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back2root:archives:denthor:part-08

PART 08 : Optimization

Hello everybody! Christmas is over, the last of the chocolates have been eaten, so it's time to get on with this, the eighth part of the ASPHYXIA Demo Trainer Series. This particular part is primarily about 3-D, but also includes a bit on optimisation.

If you are already a 3-D guru, you may as well skip this text file, have a quick look at the sample program then go back to sleep, because I am going to explain in minute detail exactly how the routines work ;)

If you would like to contact me, or the team, there are many ways you can do it :

1) Write a message to Grant Smith/Denthor/Asphyxia in private mail on the ASPHYXIA BBS.
2) Write a message in the Programming conference on the For Your Eyes Only BBS (of which I am the Moderator ) This is preferred if you have a general programming query or problem others would benefit from.
4) Write to Denthor, EzE or Goth on Connectix.
5) Write to :  Grant Smith
               P.O.Box 270 Kloof
               3640
               Natal
6) Call me (Grant Smith) at (031) 73 2129 (leave a message if you call during varsity)
7) Write to mcphail@beastie.cs.und.ac.za on InterNet, and mention the word Denthor near the top of the letter.

NB : If you are a representative of a company or BBS, and want ASPHYXIA to do you a demo, leave mail to me; we can discuss it.

NNB : If you have done/attempted a demo, SEND IT TO ME! We are feeling quite lonely and want to meet/help out/exchange code with other demo groups. What do you have to lose? Leave a message here and we can work out how to transfer it. We really want to hear from you!

Optimisation

Before I begin with the note on 3-D, I would like to stress that many of these routines, and probably most of your own, could be sped up quite a bit with a little optimisation.

One must realise, however, that you must take a look at WHAT to optimise … converting a routine that is only called once at startup into a tightly coded assembler routine may show off your merits as a coder, but does absolutely nothing to speed up your program.

Something that is called often per frame is something that needs to be as fast as possible. For some, a much used procedure is the PutPixel procedure. Here is the putpixel procedure I gave you last week:

Procedure Putpixel (X,Y : Integer; Col : Byte; where:word);
BEGIN
  Asm
    push    ds                      { 14   clock ticks }
    push    es                      { 14 }
    mov     ax,[where]              { 8  }
    mov     es,ax                   { 2 }
    mov     bx,[X]                  { 8  }
    mov     dx,[Y]                  { 8  }
    push    bx                      { 15 }
    mov     bx, dx                  { 2  }
    mov     dh, dl                  { 2  }
    xor     dl, dl                  { 3  }
    shl     bx, 1                   { 2  }
    shl     bx, 1                   { 2  }
    shl     bx, 1                   { 2  }
    shl     bx, 1                   { 2  }
    shl     bx, 1                   { 2  }
    shl     bx, 1                   { 2  }
    add     dx, bx                  { 3  }
    pop     bx                      { 12 }
    add     bx, dx                  { 3  }
    mov     di, bx                  { 2 }
    xor     al,al                   { 3  }
    mov     ah, [Col]               { 8  }
    mov     es:[di],ah              { 10 }
    pop     es                      { 12 }
    pop     ds                      { 12 }
  End;
END;

Total = 153 clock ticks

Don't take my clock ticks as gospel, I probably got one or two wrong.

Right, now for some optimising. Firstly, if you have 286 instructions turned on, you may replace the 6 shl,1 with shl,6.

Secondly, the Pascal compiler automatically pushes and pops ES, so those two lines may be removed. DS:[SI] is not altered in this procedure, so we may remove those too. Also, instead of moving COL into ah, we move it into AL and call stosb (es:[di]:=al; inc di). Let's have a look at the routine now :

Procedure Putpixel (X,Y : Integer; Col : Byte; where:word);
BEGIN
  Asm
    mov     ax,[where]              { 8  }
    mov     es,ax                   { 2 }
    mov     bx,[X]                  { 8  }
    mov     dx,[Y]                  { 8  }
    push    bx                      { 15 }
    mov     bx, dx                  { 2  }
    mov     dh, dl                  { 2  }
    xor     dl, dl                  { 3  }
    shl     bx, 6                   { 8  }
    add     dx, bx                  { 3  }
    pop     bx                      { 12 }
    add     bx, dx                  { 3  }
    mov     di, bx                  { 2 }
    mov     al, [Col]               { 8  }
    stosb                           { 11 }
  End;
END;

Total = 95 clock ticks

Now, let us move the value of BX directly into DI, thereby removing a costly push and pop. The MOV and the XOR of DX can be replaced by it's equivalent, SHL DX,8

Procedure Putpixel (X,Y : Integer; Col : Byte; where:word); assembler;
asm
    mov     ax,[where]              { 8  }
    mov     es,ax                   { 2  }
    mov     bx,[X]                  { 8  }
    mov     dx,[Y]                  { 8  }
    mov     di,bx                   { 2  }
    mov     bx, dx                  { 2  }
    shl     dx, 8                   { 8  }
    shl     bx, 6                   { 8  }
    add     dx, bx                  { 3  }
    add     di, dx                  { 3  }
    mov     al, [Col]               { 8  }
    stosb                           { 11 }
end;

Total = 71 clock ticks

As you can see, we have brought the clock ticks down from 153 ticks to 71 ticks … quite an improvement. (The current ASPHYXIA putpixel takes 48 clock ticks).

As you can see, by going through your routines a few times, you can spot and remove unnecessary instructions, thereby greatly increasing the speed of your program.

Defining a 3-D object

Drawing an object in 3-D is not that easy. Sitting down and plotting a list of X,Y and Z points can be a time consuming business. So, let us first look at the three axes you are drawing them on :

                    Y    Z
                   /|\  /
                    | /
             X<-----|----->
                    |
                   \|/

X is the horisontal axis, from left to right. Y is the vertical axis, from top to bottom. Z is the depth, going straight into the screen.

In this trainer, we are using lines, so we define 2 X,Y and Z coordinates, one for each end of the line. A line from far away, in the upper left of the X and Y axes, to close up in the bottom right of the X and Y axes, would look like this :

{       x1 y1  z1   x2  y2 z2    }
    ( (-10,10,-10),(10,-10,10) )

Rotating a point with matrixes

I thought that more then one matix are matrisese (sp), but my spellchecker insists it is matrixes, so I let it have it's way ;-)

Having a 3-D object is useless unless you can rotate it some way. For demonstration purposes, I will begin by working in two dimensions, X and Y.

Let us say you have a point, A,B, on a graph.

                      Y
                      |  /O1 (Cos (a)*A-Sin (a)*B , Sin (a)*A+Cos (a)*B)
                      |/      (A,B)
               X<-----|------O-->
                      |
                      |

Now, let us say we rotate this point by 45 degrees anti-clockwise. The new A,B can be easily be calculated using sin and cos, by an adaption of our circle algorithm, ie.

           A2:=Cos (45)*A - Sin (45)*B
           B2:=Sin (45)*A + Cos (45)*B

I recall that in standard 8 and 9, we went rather heavily into this in maths. If you have troubles, fine a 8/9/10 maths book and have a look; it will go through the proofs etc.

Anyway, we have now rotated an object in two dimensions, AROUND THE Z AXIS. In matrix form, the equation looks like this :

   [  Cos (a)   -Sin (a)      0        0     ]    [  x ]
   [  Sin (a)    Cos (a)      0        0     ]  . [  y ]
   [     0         0          1        0     ]    [  z ]
   [     0         0          0        1     ]    [  1 ]

I will not go to deeply into matrixes math at this stage, as there are many books on the subject (it is not part of matric maths, however). To multiply a matrix, to add the products of the row of the left matrix and the column of the right matrix, and repeat this for all the columns of the left matrix. I don't explain it as well as my first year maths lecturer, but have a look at how I derived A2 and B2 above. Here are the other matrixes :

Matrix for rotation around the Y axis :

   [  Cos (a)      0       -Sin (a)    0     ]    [  x ]
   [     0         1          0        0     ]  . [  y ]
   [  Sin (a)      0        Cos (a)    0     ]    [  z ]
   [     0         0          0        1     ]    [  1 ]

Matrix for rotation around the X axis :

   [     1         0                   0     ]    [  x ]
   [     0       Cos (a)   -Sin (a)    0     ]  . [  y ]
   [     0       Sin (a)    Cos (a)    0     ]    [  z ]
   [     0         0          0        1     ]    [  1 ]

By putting all these matrixes together, we can translate out 3D points around the origin of 0,0,0. See the sample program for how we put them together.

In the sample program, we have a constant, never changing base object. This is rotated into a second variable, which is then drawn. I am sure many of you can thing of cool ways to change the base object, the effects of which will appear while the object is rotating. One idea is to “pulsate” a certain point of the object according to the beat of the music being played in the background. Be creative. If you feel up to it, you could make your own version of transformers ;)

Drawing a 3D point to screen

Having a rotated 3D object is useless unless we can draw it to screen. But how do we show a 3D point on a 2D screen? The answer needs a bit of explaining. Examine the following diagram :

              |         ________-------------
          ____|___------      o Object at X,Y,Z     o1 Object at X,Y,Z2
 Eye -> O)____|___
              |   ------________
              |                 -------------- Field of vision
            Screen

Let us pretend that the centre of the screen is the horizon of our little 3D world. If we draw a three dimensional line from object “o” to the centre of the eye, and place a pixel on the X and Y coordinates where it passes through the screen, we will notice that when we do the same with object o1, the pixel is closer to the horizon, even though their 3D X and Y coords are identical, but “o1”'s Z is larger then “o”'s. This means that the further away a point is, the closer to the horizon it is, or the smaller the object will appear. That sounds right, doesent it? But, I hear you cry, how do we translate this into a formula? The answer is quite simple. Divide your X and your Y by your Z. Think about it. The larger the number you divide by, the closer to zero, or the horizon, is the result! This means, the bigger the Z, the further away is the object! Here it is in equation form :

       nx := 256*x div (z-Zoff)+Xoff
       ny := 256*y div (z-Zoff)+Yoff

Zoff is how far away the entire object is, Xoff is the objects X value, and Yoff is the objects Y value. In the sample program, Xoff start off at 160 and Yoff starts off at 100, so that the object is in the middle of the screen.

The 256 that you times by is the perspective with which you are viewing. Changing this value gives you a “fish eye” effect when viewing the object. Anyway, there you have it! Draw a pixel at nx,ny, and viola! you are now doing 3D! Easy, wasn't it?

Possible improvements

This program is not the most optimised routine you will ever encounter (;-)) … it uses 12 muls and 2 divs per point. (Asphyxia currently has 9 muls and 2 divs per point) Real math is used for all the calculations in the sample program, which is slow, so fixed point math should be implemented (I will cover fixed point math in a future trainer). The line routine currently being used is very slow. Chain-4 could be used to cut down on screen flipping times.

Color values per line should be added, base object morphing could be put in, polygons could be used instead of lines, handling of more then one object should be implemented, clipping should be added instead of not drawing something if any part of it is out of bounds.

In other words, you have a lot of work ahead of you ;)

In closing

There are a lot of books out there on 3D, and quite a few sample programs too. Have a look at them, and use the best bits to create your own, unique 3D engine, with which you can do anything you want. I am very interested in 3D (though EzE and Goth wrote most of ASPHYXIA'S 3D routines), and would like to see what you can do with it. Leave me a message through one of the means described above.

I am delving into the murky world of texture mapping. If anyone out there has some routines on the subject and are interested in swapping, give me a buzz!

What to do in future trainers? Help me out on this one! Are there any effects/areas you would like a bit of info on? Leave me a message!

I unfortunately did not get any messages regarding BBS's that carry this series, so the list that follows is the same one from last time. Give me your names, sysops!

Aaaaargh!!! Try as I might, I can't think of a new quote. Next time, I promise! ;-)

Bye for now, Denthor

These fine BBS's carry the ASPHYXIA DEMO TRAINER SERIES : (alphabetical)

╔══════════════════════════╦════════════════╦═════╦═══╦════╦════╗
║BBS Name                  ║Telephone No.   ║Open ║Msg║File║Past║
╠══════════════════════════╬════════════════╬═════╬═══╬════╬════╣
║ASPHYXIA BBS #1           ║(031) 765-5312  ║ALL  ║ * ║ *  ║ *  ║
║ASPHYXIA BBS #2           ║(031) 765-6293  ║ALL  ║ * ║ *  ║ *  ║
║Connectix BBS             ║(031) 266-9992  ║ALL  ║ * ║    ║    ║
║For Your Eyes Only BBS    ║(031) 285-318   ║A/H  ║ * ║ *  ║ *  ║
╚══════════════════════════╩════════════════╩═════╩═══╩════╩════╝

Open = Open at all times or only A/H Msg = Available in message base File = Available in file base Past = Previous Parts available

Code Source

PASCAL

(*****************************************************************************)
(*                                                                           *)
(* TUT8.PAS - VGA Trainer Program 8 (in Pascal)                              *)
(*                                                                           *)
(* "The VGA Trainer Program" is written by Denthor of Asphyxia.  However it  *)
(* was limited to Pascal only in its first run.  All I have done is taken    *)
(* his original release, translated it to C++, and touched up a few things.  *)
(* I take absolutely no credit for the concepts presented in this code, and  *)
(* am NOT the person to ask for help if you are having trouble.  -Snowman    *)
(*                                                                           *)
(* Program Notes : This program presents the basis of 3D.                    *)
(*                                                                           *)
(* Author        : Grant Smith (Denthor)  - denthor@beastie.cs.und.ac.za     *)
(*                                                                           *)
(*****************************************************************************)
 
{$X+}
USES Crt;
 
CONST VGA = $A000;
      MaxLines = 12;
      Obj : Array [1..MaxLines,1..2,1..3] of integer =
        (
        ((-10,-10,-10),(10,-10,-10)),((-10,-10,-10),(-10,10,-10)),
        ((-10,10,-10),(10,10,-10)),((10,-10,-10),(10,10,-10)),
        ((-10,-10,10),(10,-10,10)),((-10,-10,10),(-10,10,10)),
        ((-10,10,10),(10,10,10)),((10,-10,10),(10,10,10)),
        ((-10,-10,10),(-10,-10,-10)),((-10,10,10),(-10,10,-10)),
        ((10,10,10),(10,10,-10)),((10,-10,10),(10,-10,-10))
        );  { The 3-D coordinates of our object ... stored as (X1,Y1,Z1), }
            { (X2,Y2,Z2) ... for the two ends of a line }
 
 
Type Point = Record
               x,y,z:real;                { The data on every point we rotate}
             END;
     Virtual = Array [1..64000] of byte;  { The size of our Virtual Screen }
     VirtPtr = ^Virtual;                  { Pointer to the virtual screen }
 
 
VAR Lines : Array [1..MaxLines,1..2] of Point;  { The base object rotated }
    Translated : Array [1..MaxLines,1..2] of Point; { The rotated object }
    Xoff,Yoff,Zoff:Integer;               { Used for movement of the object }
    lookup : Array [0..360,1..2] of real; { Our sin and cos lookup table }
    Virscr : VirtPtr;                     { Our first Virtual screen }
    Vaddr  : word;                        { The segment of our virtual screen}
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure SetMCGA;  { This procedure gets you into 320x200x256 mode. }
BEGIN
  asm
     mov        ax,0013h
     int        10h
  end;
END;
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure SetText;  { This procedure returns you to text mode.  }
BEGIN
  asm
     mov        ax,0003h
     int        10h
  end;
END;
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure Cls (Where:word;Col : Byte);
   { This clears the screen to the specified color }
BEGIN
     asm
        push    es
        mov     cx, 32000;
        mov     es,[where]
        xor     di,di
        mov     al,[col]
        mov     ah,al
        rep     stosw
        pop     es
     End;
END;
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure SetUpVirtual;
   { This sets up the memory needed for the virtual screen }
BEGIN
  GetMem (VirScr,64000);
  vaddr := seg (virscr^);
END;
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure ShutDown;
   { This frees the memory used by the virtual screen }
BEGIN
  FreeMem (VirScr,64000);
END;
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
procedure flip(source,dest:Word);
  { This copies the entire screen at "source" to destination }
begin
  asm
    push    ds
    mov     ax, [Dest]
    mov     es, ax
    mov     ax, [Source]
    mov     ds, ax
    xor     si, si
    xor     di, di
    mov     cx, 32000
    rep     movsw
    pop     ds
  end;
end;
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure Pal(Col,R,G,B : Byte);
  { This sets the Red, Green and Blue values of a certain color }
Begin
   asm
      mov    dx,3c8h
      mov    al,[col]
      out    dx,al
      inc    dx
      mov    al,[r]
      out    dx,al
      mov    al,[g]
      out    dx,al
      mov    al,[b]
      out    dx,al
   end;
End;
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Function rad (theta : real) : real;
  {  This calculates the degrees of an angle }
BEGIN
  rad := theta * pi / 180
END;
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure SetUpPoints;
  { This sets the basic offsets of the object, creates the lookup table and
    moves the object from a constant to a variable }
VAR loop1:integer;
BEGIN
  Xoff:=160;
  Yoff:=100;
  Zoff:=-256;
  For loop1:=0 to 360 do BEGIN
    lookup [loop1,1]:=sin (rad (loop1));
    lookup [loop1,2]:=cos (rad (loop1));
  END;
  For loop1:=1 to MaxLines do BEGIN
    Lines [loop1,1].x:=Obj [loop1,1,1];
    Lines [loop1,1].y:=Obj [loop1,1,2];
    Lines [loop1,1].z:=Obj [loop1,1,3];
    Lines [loop1,2].x:=Obj [loop1,2,1];
    Lines [loop1,2].y:=Obj [loop1,2,2];
    Lines [loop1,2].z:=Obj [loop1,2,3];
  END;
END;
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure Putpixel (X,Y : Integer; Col : Byte; where:word);
  { This puts a pixel on the screen by writing directly to memory. }
BEGIN
  Asm
    mov     ax,[where]
    mov     es,ax
    mov     bx,[X]
    mov     dx,[Y]
    mov     di,bx
    mov     bx, dx                  {; bx = dx}
    shl     dx, 8
    shl     bx, 6
    add     dx, bx                  {; dx = dx + bx (ie y*320)}
    add     di, dx                  {; finalise location}
    mov     al, [Col]
    stosb
  End;
END;
 
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure Line(a,b,c,d:integer;col:byte;where:word);
  { This draws a solid line from a,b to c,d in colour col }
  function sgn(a:real):integer;
  begin
       if a>0 then sgn:=+1;
       if a<0 then sgn:=-1;
       if a=0 then sgn:=0;
  end;
var i,s,d1x,d1y,d2x,d2y,u,v,m,n:integer;
begin
     u:= c - a;
     v:= d - b;
     d1x:= SGN(u);
     d1y:= SGN(v);
     d2x:= SGN(u);
     d2y:= 0;
     m:= ABS(u);
     n := ABS(v);
     IF NOT (M>N) then
     BEGIN
          d2x := 0 ;
          d2y := SGN(v);
          m := ABS(v);
          n := ABS(u);
     END;
     s := m shr 1;
     FOR i := 0 TO m DO
     BEGIN
          putpixel(a,b,col,where);
          s := s + n;
          IF not (s<m) THEN
          BEGIN
               s := s - m;
               a:= a + d1x;
               b := b + d1y;
          END
          ELSE
          BEGIN
               a := a + d2x;
               b := b + d2y;
          END;
     end;
END;
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure DrawLogo;
  { This draws 'ASPHYXIA' at the top of the screen in little balls }
CONST ball : Array [1..5,1..5] of byte =
         ((0,1,1,1,0),
          (1,4,3,2,1),
          (1,3,3,2,1),
          (1,2,2,2,1),
          (0,1,1,1,0));
 
VAR Logo : Array [1..5] of String;
    loop1,loop2,loop3,loop4:integer;
BEGIN
  pal (13,0,63,0);
  pal (1,0,0,40);
  pal (2,0,0,45);
  pal (3,0,0,50);
  pal (4,0,0,60);
  Logo[1]:=' O  OOO OOO O O O O O O OOO  O ';
  Logo[2]:='O O O   O O O O O O O O  O  O O';
  Logo[3]:='OOO OOO OOO OOO  O   O   O  OOO';
  Logo[4]:='O O   O O   O O  O  O O  O  O O';
  Logo[5]:='O O OOO O   O O  O  O O OOO O O';
  For loop1:=1 to 5 do
    For loop2:=1 to 31 do
      if logo[loop1][loop2]='O' then
        For loop3:=1 to 5 do
          For loop4:=1 to 5 do
            putpixel (loop2*10+loop3,loop1*4+loop4,ball[loop3,loop4],vaddr);
END;
 
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure RotatePoints (X,Y,Z:Integer);
  { This rotates object lines by X,Y and Z; then places the result in
    TRANSLATED }
VAR loop1:integer;
    temp:point;
BEGIN
  For loop1:=1 to maxlines do BEGIN
    temp.x:=lines[loop1,1].x;
    temp.y:=lookup[x,2]*lines[loop1,1].y - lookup[x,1]*lines[loop1,1].z;
    temp.z:=lookup[x,1]*lines[loop1,1].y + lookup[x,2]*lines[loop1,1].z;
 
    translated[loop1,1]:=temp;
 
    If y>0 then BEGIN
      temp.x:=lookup[y,2]*translated[loop1,1].x - lookup[y,1]*translated[loop1,1].y;
      temp.y:=lookup[y,1]*translated[loop1,1].x + lookup[y,2]*translated[loop1,1].y;
      temp.z:=translated[loop1,1].z;
      translated[loop1,1]:=temp;
    END;
 
    If z>0 then BEGIN
      temp.x:=lookup[z,2]*translated[loop1,1].x + lookup[z,1]*translated[loop1,1].z;
      temp.y:=translated[loop1,1].y;
      temp.z:=-lookup[z,1]*translated[loop1,1].x + lookup[z,2]*translated[loop1,1].z;
      translated[loop1,1]:=temp;
    END;
 
    temp.x:=lines[loop1,2].x;
    temp.y:=cos (rad(X))*lines[loop1,2].y - sin (rad(X))*lines[loop1,2].z;
    temp.z:=sin (rad(X))*lines[loop1,2].y + cos (rad(X))*lines[loop1,2].z;
 
    translated[loop1,2]:=temp;
 
    If y>0 then BEGIN
      temp.x:=cos (rad(Y))*translated[loop1,2].x - sin (rad(Y))*translated[loop1,2].y;
      temp.y:=sin (rad(Y))*translated[loop1,2].x + cos (rad(Y))*translated[loop1,2].y;
      temp.z:=translated[loop1,2].z;
      translated[loop1,2]:=temp;
    END;
 
    If z>0 then BEGIN
      temp.x:=cos (rad(Z))*translated[loop1,2].x + sin (rad(Z))*translated[loop1,2].z;
      temp.y:=translated[loop1,2].y;
      temp.z:=-sin (rad(Z))*translated[loop1,2].x + cos (rad(Z))*translated[loop1,2].z;
      translated[loop1,2]:=temp;
    END;
  END;
END;
 
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure DrawPoints;
  { This draws the translated object to the virtual screen }
VAR loop1:Integer;
    nx,ny,nx2,ny2:integer;
    temp:integer;
BEGIN
  For loop1:=1 to MaxLines do BEGIN
    If (translated[loop1,1].z+zoff<0) and (translated[loop1,2].z+zoff<0) then BEGIN
      temp:=round (translated[loop1,1].z+zoff);
      nx :=round (256*translated[loop1,1].X) div temp+xoff;
      ny :=round (256*translated[loop1,1].Y) div temp+yoff;
      temp:=round (translated[loop1,2].z+zoff);
      nx2:=round (256*translated[loop1,2].X) div temp+xoff;
      ny2:=round (256*translated[loop1,2].Y) div temp+yoff;
      If (NX > 0) and (NX < 320) and (NY > 25) and (NY < 200) and
         (NX2> 0) and (NX2< 320) and (NY2> 25) and (NY2< 200) then
           line (nx,ny,nx2,ny2,13,vaddr);
    END;
  END;
END;
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure ClearPoints;
  { This clears the translated object from the virtual screen ... believe it
    or not, this is faster then a straight "cls (vaddr,0)" }
VAR loop1:Integer;
    nx,ny,nx2,ny2:Integer;
    temp:integer;
BEGIN
  For loop1:=1 to MaxLines do BEGIN
    If (translated[loop1,1].z+zoff<0) and (translated[loop1,2].z+zoff<0) then BEGIN
      temp:=round (translated[loop1,1].z+zoff);
      nx :=round (256*translated[loop1,1].X) div temp+xoff;
      ny :=round (256*translated[loop1,1].Y) div temp+yoff;
      temp:=round (translated[loop1,2].z+zoff);
      nx2:=round (256*translated[loop1,2].X) div temp+xoff;
      ny2:=round (256*translated[loop1,2].Y) div temp+yoff;
      If (NX > 0) and (NX < 320) and (NY > 25) and (NY < 200) and
         (NX2> 0) and (NX2< 320) and (NY2> 25) and (NY2< 200) then
           line (nx,ny,nx2,ny2,0,vaddr);
    END;
  END;
END;
 
 
{ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ}
Procedure MoveAround;
  { This is the main display procedure. Firstly it brings the object towards
    the viewer by increasing the Zoff, then passes control to the user }
VAR deg,loop1:integer;
    ch:char;
BEGIN
  deg:=0;
  ch:=#0;
  Cls (vaddr,0);
  DrawLogo;
  For loop1:=-256 to -40 do BEGIN
    zoff:=loop1*2;
    RotatePoints (deg,deg,deg);
    DrawPoints;
    flip (vaddr,vga);
    ClearPoints;
    deg:=(deg+5) mod 360;
  END;
 
  Repeat
    if keypressed then BEGIN
      ch:=upcase (Readkey);
      Case ch of 'A' : zoff:=zoff+5;
                 'Z' : zoff:=zoff-5;
                 ',' : xoff:=xoff-5;
                 '.' : xoff:=xoff+5;
                 'S' : yoff:=yoff-5;
                 'X' : yoff:=yoff+5;
      END;
    END;
    DrawPoints;
    flip (vaddr,vga);
    ClearPoints;
    RotatePoints (deg,deg,deg);
    deg:=(deg+5) mod 360;
  Until ch=#27;
END;
 
 
BEGIN
  SetUpVirtual;
  Writeln ('Greetings and salutations! Hope you had a great Christmas and New');
  Writeln ('year! ;-) ... Anyway, this tutorial is on 3-D, so this is what is');
  Writeln ('going to happen ... a wireframe square will come towards you.');
  Writeln ('When it gets close, you get control. "A" and "Z" control the Z');
  Writeln ('movement, "," and "." control the X movement, and "S" and "X"');
  Writeln ('control the Y movement. I have not included rotation control, but');
  Writeln ('it should be easy enough to put in yourself ... if you have any');
  Writeln ('hassles, leave me mail.');
  Writeln;
  Writeln ('Read the main text file for ideas on improving this code ... and');
  Writeln ('welcome to the world of 3-D!');
  writeln;
  writeln;
  Write ('  Hit any key to contine ...');
  Readkey;
  SetMCGA;
  SetUpPoints;
  MoveAround;
  SetText;
  ShutDown;
  Writeln ('All done. This concludes the eigth sample program in the ASPHYXIA');
  Writeln ('Training series. You may reach DENTHOR under the names of GRANT');
  Writeln ('SMITH/DENTHOR/ASPHYXIA on the ASPHYXIA BBS. I am also an avid');
  Writeln ('Connectix BBS user, and occasionally read RSAProg.');
  Writeln ('For discussion purposes, I am also the moderator of the Programming');
  Writeln ('newsgroup on the For Your Eyes Only BBS.');
  Writeln ('The numbers are available in the main text. You may also write to me at:');
  Writeln ('             Grant Smith');
  Writeln ('             P.O. Box 270');
  Writeln ('             Kloof');
  Writeln ('             3640');
  Writeln ('I hope to hear from you soon!');
  Writeln; Writeln;
  Write   ('Hit any key to exit ...');
  Readkey;
END.

C

file:tut8.cpp
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// TUTPROG8.CPP - VGA Trainer Program 8 (in Turbo C++ 3.0)                 //
//                                                                         //
// "The VGA Trainer Program" is written by Denthor of Asphyxia. However it //
// was limited to only Pascal in its first run.  All I have done is taken  //
// his original release, translated it to C++ and touched up a few things. //
// I take absolutely no credit for the concepts presented in this code and //
// am NOT the person to ask for help if you are having trouble.            //
//                                                                         //
// Program Notes : This program presents the basics of 3D.  Please note    //
//                 that the compiled C++ version of this program runs      //
//                 much faster than the Pascal version.  If you are        //
//                 a 486DX/33 or higher, you may wish to turn turbo off.   //
//                                                                         //
//                 If you are compiling this program from within the       //
//                 Turbo C++ environment, you must go under Options,       //
//                 Debugger, and change the "Program Heap Size" to a value //
//                 80 or greater.  If you are going to be fooling around   //
//                 with the code a bit, I suggest raising this to about    //
//                 100 just to be on the safe side.  You don't have to     //
//                 worry about this if you are compiling command line.     //
//                                                                         //
//                 Just for reference, this is what I use:                 //
//                                                                         //
//                    tcc -mc -a -G -2 -O tut8.cpp                         //
//                                                                         //
//                 The way things are set up, there is no need to compile  //
//                 or link tut8.cpp and gfx1.cpp seperately.               //
//                                                                         //
//                 The Compact memory model (-mc) seems to provide the     //
//                 best results for this tutorial.  Remember, use this     //
//                 memory model when you have little code (less than 64k)  //
//                 and lots of data.                                       //
//                                                                         //
// Author        : Grant Smith (Denthor) - denthor@beastie.cs.und.ac.za    //
// Translator    : Christopher G. Mann   - r3cgm@dax.cc.uakron.edu         //
//                                                                         //
// Last Modified : January 14, 1995                                        //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
//               //
// INCLUDE FILES //
//               //
 
  #include <alloc.h>
                           // farcalloc()
  #include <conio.h>
                           // clrscr(), getch(), kbhit()
  #include <dos.h>
                           // FP_SEG, geninterrupt()
  #include <iostream.h>
                           // cout
  #include <math.h>
                           // sin(), cos()
  #include <stdlib.h>
                           // exit()
  #include "gfx1.cpp"
 
//          //
// TYPEDEFS //
//          //
 
  typedef unsigned char byte;
  typedef unsigned int  word;
 
//           //
// CONSTANTS //
//           //
 
  const MAXLINES = 12;     // the number of lines in our cube
 
  // The 3-D coordinates of our object ... stored as {X1,Y1,Z1},
  // {X2,Y2,Z2} ... for the two ends of a line
  const int Obj[MAXLINES][2][3] =
    { {{-10,-10,-10}, { 10,-10,-10}}, //  0        .-----2----.
      {{-10,-10,-10}, {-10, 10,-10}}, //  1       /|         /|
      {{-10, 10,-10}, { 10, 10,-10}}, //  2      9 |        A |
      {{ 10,-10,-10}, { 10, 10,-10}}, //  3     /  |       /  |
      {{-10,-10, 10}, { 10,-10, 10}}, //  4    .------6---.   3
      {{-10,-10, 10}, {-10, 10, 10}}, //  5    |   |      |   |
      {{-10, 10, 10}, { 10, 10, 10}}, //  6    |   1      7   |
      {{ 10,-10, 10}, { 10, 10, 10}}, //  7    |   |      |   |
      {{-10,-10, 10}, {-10,-10,-10}}, //  8    5   '----0-|---'
      {{-10, 10, 10}, {-10, 10,-10}}, //  9    |  /       |  /
      {{ 10, 10, 10}, { 10, 10,-10}}, //  A    | 8        | B
      {{ 10,-10, 10}, { 10,-10,-10}}  //  B    |/         |/
    };                                //       `-----4----'
 
//                     //
// FUNCTION PROTOTYPES //
//                     //
 
  // MEMORY ALLOCATION FUNCTIONS
  void SetUpVirtual ();
  void ShutDown     ();
 
  // LOGO-FUNCTION
  void DrawLogo     ();
 
  // 3D POINTS FUNCTIONS
  void SetUpPoints  ();
  void RotatePoints (int X, int Y, int Z);
  void DrawPoints   ();
  void ClearPoints  ();
 
  // MID-LEVEL FUNCTION
  void MoveAround   ();
 
//            //
// STRUCTURES //
//            //
 
  // The data on every point we rotate
  struct Point {
    float    x;
    float    y;
    float    z;
  };
 
//                              //
// GLOBAL VARIABLE DECLARATIONS //
//                              //
 
  byte far *Virscr=NULL;           // Pointer to our virtual screen
  word Vaddr;                      // Segment of our virtual screen
  float Lookup[360][2];            // Our sin and cos lookup table
  int Xoff, Yoff, Zoff;            // Used for movement of the objects
  Point Lines[MAXLINES][2];        // The base object rotated
  Point Translated[MAXLINES][2];   // The rotated object
 
 
///////////////////////////////////////////////////////////////////////////////
//                                                                           //
//                                MAIN FUNCTION                              //
//                                                                           //
///////////////////////////////////////////////////////////////////////////////
 
void main() {
 
  SetUpVirtual();
  clrscr();
  cout
    << "Greetings and salutations! Hope you had a great Christmas and New\n"
    << "year! ;-) ... Anyway, this tutorial is on 3-D, so this is what is\n"
    << "going to happen ... a wireframe square will come towards you.\n"
    << "When it gets close, you get control. ""A"" and ""Z"" control the Z\n"
    << "movement, "","" and ""."" control the X movement, and ""S"" and ""X""\n"
    << "control the Y movement. I have not included rotation control, but\n"
    << "it should be easy enough to put in yourself ... if you have any\n"
    << "hassles, leave me mail.\n\n";
  cout
    << "Read the main text file for ideas on improving this code ... and\n"
    << "welcome to the world of 3-D!\n\n";
  cout << "Hit any key to contine ...\n";
  getch();
 
  SetMCGA();
 
  SetUpPoints();
  MoveAround();
 
  ShutDown();
  SetText();
 
  cout
    << "All done. This concludes the eigth sample program in the ASPHYXIA\n"
    << "Training series. You may reach DENTHOR under the names of GRANT\n"
    << "SMITH/DENTHOR/ASPHYXIA on the ASPHYXIA BBS. I am also an avid\n"
    << "Connectix BBS user, and occasionally read RSAProg.\n"
    << "For discussion purposes, I am also the moderator of the Programming\n"
    << "newsgroup on the For Your Eyes Only BBS.\n"
    << "The numbers are available in the main text. You may also write to me at:\n"
    << "             Grant Smith\n"
    << "             P.O. Box 270\n"
    << "             Kloof\n"
    << "             3640\n"
    << "I hope to hear from you soon!\n\n\n";
  cout << "Hit any key to exit ...\n";
  getch();
 
}
 
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// SetUpVirtual() - This sets up the memory needed for the virtual screen. //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void SetUpVirtual() {
 
  Virscr = (byte far *) farcalloc(64000,1);
 
  // always check to see if enough memory was allocated
  if (Virscr == NULL) {
    SetText();
    cout << "Insufficient memory for virtual screens, exiting...";
    exit(1);
  }
 
  Vaddr = FP_SEG(Virscr);
 
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// ShutDown() - This frees the memory used by the virtual screen.          //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void ShutDown() {
  free(Virscr);
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// DrawLogo() - This draws 'SNOWMAN' at the top of the screen in little    //
//              balls.                                                     //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void DrawLogo() {
 
  const byte ball[5][5] = { 0,1,1,1,0,
                            1,4,3,2,1,
                            1,3,3,2,1,
                            1,2,2,2,1,
                            0,1,1,1,0
                          };
 
  const char *Logo[5] = { {"OOO OOO OOO O O O  O O  OOO OOO"},
                          {"O   O O O O O O O O O O O O O O"},
                          {"OOO O O O O O O O O O O OOO O O"},
                          {"  O O O O O O O O O O O O O O O"},
                          {"OOO O O OOO  O O  O O O O O O O"}
                        };
 
  int loop1, loop2, loop3, loop4;
 
  Pal(13, 0,63, 0); // set the color for the cube lines
  Pal( 1, 0, 0,40); // set the colors for the dots
  Pal( 2, 0, 0,45);
  Pal( 3, 0, 0,50);
  Pal( 4, 0, 0,60);
 
  for (loop1=0; loop1<5; loop1++)        // for each line...
    for (loop2=0; loop2<31; loop2++)       // is it active?
      if (Logo[loop1][loop2] == 'O')
      for (loop3=0; loop3<5; loop3++)        // y coordinate of the ball
        for (loop4=0; loop4<5; loop4++)        // x coordinate of the ball
          Putpixel ((loop2+1)*10+loop3, (loop1+1)*4+loop4,
                    ball[loop3][loop4],Vaddr);
 
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// SetUpPoints() - This sets the basic offsets of the object, creates the  //
//                 lookup table, and moves the object from a constant to a //
//                 variable.                                               //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void SetUpPoints() {
 
  int loop1;
 
  // set the starting offsets of the cube
  Xoff =  160;
  Yoff =  100;
  Zoff = -256;
 
  // generate the sin() and cos() tables
  for (loop1=0; loop1<361; loop1++) {
    Lookup [loop1][0] = sin(rad(loop1));
    Lookup [loop1][1] = cos(rad(loop1));
  }
 
  // move the Obj constant array into the Lines array
  for (loop1=0; loop1<MAXLINES; loop1++) {
    Lines[loop1][0].x = Obj[loop1][0][0];
    Lines[loop1][0].y = Obj[loop1][0][1];
    Lines[loop1][0].z = Obj[loop1][0][2];
    Lines[loop1][1].x = Obj[loop1][1][0];
    Lines[loop1][1].y = Obj[loop1][1][1];
    Lines[loop1][1].z = Obj[loop1][1][2];
  }
 
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// RotatePoints() - This rotates object lines by X, Y, and Z.  Then it     //
//                  places the result in Translated.                       //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void RotatePoints (int X,int Y,int Z) {
 
  int loop1;
  Point temp;
 
  // for each line...
  for (loop1=0; loop1<MAXLINES; loop1++) {
 
    // start point of line
 
    temp.x = Lines[loop1][0].x;
    temp.y = Lookup[X][1]*Lines[loop1][0].y - Lookup[X][0]*Lines[loop1][0].z;
    temp.z = Lookup[X][0]*Lines[loop1][0].y + Lookup[X][1]*Lines[loop1][0].z;
    Translated[loop1][0] = temp;
 
    if (Y > 0) {
      temp.x = Lookup[Y][1]*Translated[loop1][0].x - Lookup[Y][0]*Translated[loop1][0].y;
      temp.y = Lookup[Y][0]*Translated[loop1][0].x + Lookup[Y][1]*Translated[loop1][0].y;
      temp.z = Translated[loop1][0].z;
      Translated[loop1][0] =temp;
    }
 
    if (Z > 0) {
      temp.x = Lookup[Z][1]*Translated[loop1][0].x + Lookup[Z][0]*Translated[loop1][0].z;
      temp.y = Translated[loop1][0].y;
      temp.z = (-Lookup[Z][0])*Translated[loop1][0].x + Lookup[Z][1]*Translated[loop1][0].z;
      Translated[loop1][0] = temp;
    }
 
    // end point of line
 
    temp.x = Lines[loop1][1].x;
    temp.y = cos(rad(X))*Lines[loop1][1].y - sin(rad(X))*Lines[loop1][1].z;
    temp.z = sin(rad(X))*Lines[loop1][1].y + cos(rad(X))*Lines[loop1][1].z;
    Translated[loop1][1] = temp;
 
    if (Y > 0) {
      temp.x = cos(rad(X))*Translated[loop1][1].x - sin(rad(Y))*Translated[loop1][1].y;
      temp.y = sin(rad(Y))*Translated[loop1][1].x + cos(rad(Y))*Translated[loop1][1].y;
      temp.z = Translated[loop1][1].z;
      Translated[loop1][1] = temp;
    }
 
    if (Z > 0) {
      temp.x = cos(rad(Z))*Translated[loop1][1].x + sin(rad(Z))*Translated[loop1][1].z;
      temp.y = Translated[loop1][1].y;
      temp.z = (-sin(rad(Z)))*Translated[loop1][1].x + cos(rad(Z))*Translated[loop1][1].z;
      Translated[loop1][1] = temp;
    }
  }
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// DrawPoints() - This draws the translated object to the virtual screen.  //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void DrawPoints() {
 
  int loop1, nx, ny, nx2, ny2, temp;
 
  for (loop1=0; loop1<MAXLINES; loop1++) {
    if ((Translated[loop1][0].z+Zoff<0) && (Translated[loop1][1].z+Zoff<0)) {
 
      // start point of line
      temp = Translated[loop1][0].z + Zoff;
      nx   = ((256*Translated[loop1][0].x) / temp) + Xoff;
      ny   = ((256*Translated[loop1][0].y) / temp) + Yoff;
 
      // end point of line
      temp = Translated[loop1][1].z + Zoff;
      nx2  = ((256*Translated[loop1][1].x) / temp) + Xoff;
      ny2  = ((256*Translated[loop1][1].y) / temp) + Yoff;
 
      // check to make sure the line is within bounds
      if ((nx >-1) && (nx <320) && (ny >25) && (ny <200) &&
          (nx2>-1) && (nx2<320) && (ny2>25) && (ny2<200))
        Line(nx,ny,nx2,ny2,13,Vaddr);
    }
  }
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// ClearPoints() - This clears the translated object from the virtual      //
//                 screen ... believe it or not, this is faster than a     //
//                 straight cls(0,vaddr);                                  //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void ClearPoints() {
 
  int loop1, nx, ny, nx2, ny2, temp;
 
  for (loop1=0; loop1<MAXLINES; loop1++) {
    if ((Translated[loop1][0].z+Zoff<0) && (Translated[loop1][1].z+Zoff<0)) {
 
      // start point of line
      temp = Translated[loop1][0].z + Zoff;
      nx   = ((256*Translated[loop1][0].x) / temp) + Xoff;
      ny   = ((256*Translated[loop1][0].y) / temp) + Yoff;
 
      // end point of line
      temp = Translated[loop1][1].z + Zoff;
      nx2  = ((256*Translated[loop1][1].x) / temp) + Xoff;
      ny2  = ((256*Translated[loop1][1].y) / temp) + Yoff;
 
      // check to make sure the line is within bounds
      if ((nx >-1) && (nx <320) && (ny >25) && (ny <200) &&
          (nx2>-1) && (nx2<320) && (ny2>25) && (ny2<200))
        Line(nx,ny,nx2,ny2,0,Vaddr);
    }
  }
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// MoveAround() - This is the main display function.  First it brings the  //
//                object towards the viewer by increasing the Zoff, then   //
//                it passes control to the user.                           //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void MoveAround() {
 
  // For some reason, the values we defined Xoff, Yoff, and Zoff to be in
  // the function SetUpPoints() won't hold until this point.  If you know
  // the reason, please send it to r3cgm@dax.cc.uakron.edu
  Xoff =  160;  // redefined
  Yoff =  100;  // redefined
  Zoff = -256;  // redefined
 
  int deg=0, loop1;
  byte ch=1; // assign a dummy value to ch
 
  Cls(0,Vaddr);
 
  DrawLogo();
 
  for (loop1=(-256); loop1<(-39); loop1++) {
    Zoff = loop1 * 2;
    RotatePoints(deg,deg,deg);
    DrawPoints();
    Flip(Vaddr,VGA);
    ClearPoints();
    deg = (deg + 5) % 360;
  }
 
  do {
 
    if (kbhit()) {
      ch = getch();
      switch (ch) {
        // We are not going to use toupper() because if we did, we'd have
        // to include the whole ctype.h file.  This might take a little more
        // time, but the program will be smaller.  We already have 7 include
        // files, and its getting a bit rediculous.
        case 'A': case 'a': Zoff += 5; break;  // away
        case 'Z': case 'z': Zoff -= 5; break;  // toward
        case ',':           Xoff -= 5; break;  // left
        case '.':           Xoff += 5; break;  // right
        case 'S': case 's': Yoff -= 5; break;  // down
        case 'X': case 'x': Yoff += 5; break;  // up
      }
    }
    DrawPoints();
    Flip(Vaddr,VGA);
    ClearPoints();
    RotatePoints(deg,deg,deg);
    deg = (deg + 5) % 360;
 
    // if the key pressed above was 0 (i.e. a control character) then
    // read the character code
    if (ch == 0) ch = getch();
 
  } while (ch != 27); // if the escape code was 27 (escape key) then exit
}
file:gfx1.cpp
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// GFX1.CPP - VGA Trainer Program secondary module containing graphics     //
//            functions.  Note: This module does not follow a lot of good  //
//            programming practices.  It was built to be used with the     //
//            VGA tutorial series.  If you are planning on using this      //
//            module with a different source file, some modifications may  //
//            be necessary.                                                //
//                                                                         //
// Author        : Grant Smith (Denthor) - denthor@beastie.cs.und.ac.za    //
// Translator    : Christopher G. Mann   - r3cgm@dax.cc.uakron.edu         //
//                                                                         //
// Last Modified : January 13, 1995                                        //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
//               //
// INCLUDE FILES //
//               //
 
  #include <dos.h>
                           // geninterrupt()
  #include <math.h>
                           // abs()
 
//         //
// DEFINES //
//         //
 
  #if !defined(PI)
    #define PI 3.1415927
  #endif
 
  #if !defined(VGA)
    #define VGA 0xA000
  #endif
 
//          //
// TYPEDEFS //
//          //
 
  typedef unsigned char byte;
  typedef unsigned int  word;
 
//                     //
// FUNCTION PROTOTYPES //
//                     //
 
  // MODE SETTING FUNCTIONS
  void  SetMCGA     ();
  void  SetText     ();
 
  // PALLETTE FUNCTIONS
  void  Pal         (byte Col, byte  R, byte  G, byte  B);
  void  GetPal      (byte Col, byte &R, byte &G, byte &B);
 
  // MATH-LIKE FUNCTIONS
  float rad         (float theta);
  int   sgn         (int a);
 
  // DRAWING FUNCTIONS
  void  Putpixel    (word X, word Y, byte Col, word Where);
  void  Line        (int a, int b, int c, int  d, int col, word Where);
 
  // VIDEO MEMORY FUNCTIONS
  void  Cls         (byte Col, word Where);
  void  Flip        (word source, word dest);
 
 
//--------------------------MODE SETTING FUNCTIONS-------------------------//
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// SetMCGA() - This function gets you into 320x200x256 mode.               //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void SetMCGA() {
  _AX = 0x0013;
  geninterrupt (0x10);
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// SetText() - This function gets you into text mode.                      //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void SetText() {
  _AX = 0x0003;
  geninterrupt (0x10);
}
 
 
//----------------------------PALLETTE FUNCTIONS---------------------------//
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// Pal() - This sets the Red, Green, and Blue values of a certain color.   //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void Pal (byte Col, byte  R, byte  G, byte  B) {
  asm {
    mov     dx, 0x3C8    // load DX with 3C8 (write pallette function)
    mov     al, [Col]    // move color to AL
    out     dx, al       // write DX to the VGA (tell VGA that we want to
                         //   work with the color in AL
    inc     dx           // load DX with 3C9 (write RGB colors)
    mov     al, [R]      // move Red   to AL
    out     dx, al       // write DX to VGA (tell VGA that we want to use
                         //   the Red value in AL
    mov     al, [G]      // move Green to AL
    out     dx, al       // write DX to VGA
    mov     al, [B]      // move Blue  to AL
    out     dx, al       // write DX to VGA
  }
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// GetPal() - This reads the values of the Red, Green, and Blue values of  //
//            a certain color.  This function uses pass-by-reference.      //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void GetPal (byte Col, byte &R, byte &G, byte &B) {
 
  byte rr,gg,bb;
 
  asm {
    mov     dx, 0x03C7   // load DX with 3C7 (read pallette function)
    mov     al, [Col]    // move color to AL
    out     dx, al       // write DX to the VGA (tell VGA that we want to
                         //   work with the color in AL
    add     dx, 2        // load DX with 3C9 (read RGB colors)
    in      al, dx       // read Red   to AL
    mov     [rr],al      // copy AL to rr
    in      al, dx       // read Green to AL
    mov     [gg],al      // copy AL to gg
    in      al, dx       // read Blue  to AL
    mov     [bb],al      // copy AL to bb
  }
 
  R = rr;
  G = gg;
  B = bb;
 
}
 
 
//----------------------------MATH-LIKE FUNCTIONS--------------------------//
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// rad() - This calculates the degrees of an angle.                        //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
float rad(float theta) {
  return ((theta * PI)/180);
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// sgn() - This checks the sign of an integer and returns a 1, -1, or 0.   //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
int sgn (int a) {
 
  if (a > 0)  return +1;
  if (a < 0)  return -1;
  return 0;
}
 
 
//-----------------------------DRAWING FUNCTIONS---------------------------//
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// Putpixel() - This puts a pixel on the screen by writing directly to     //
//              memory.                                                    //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void Putpixel (word X, word Y, byte Col, word Where) {
  asm {
    push    ds           // save DS
    push    es           // save ES
    mov     ax, [Where]  // move segment of Where to AX
    mov     es, ax       // set ES to segment of Where
    mov     bx, [X]      // set BX to X
    mov     dx, [Y]      // set DX to Y
    push    bx           // save BX (our X value)
    mov     bx, dx       // now BX and DX are equal to Y
    mov     dh, dl       // copy DL to DH (multiply Y by 256)
    xor     dl, dl       // zero out DL
    shl     bx, 6        // shift BX left 6 places (multiply Y by 64).
    add     dx, bx       // add BX to DX (Y*64 + Y*256 = Y*320)
    pop     bx           // restore BX (X coordinate)
    add     bx, dx       // add BX to DX (Y*320 + X).  this gives you
                         //   the offset in memory you want
    mov     di, bx       // move the offset to DI
    xor     al, al       // zero out AL
    mov     ah, [Col]    // move value of Col into AH
    mov     es:[di], ah  // move Col to the offset in memory (DI)
    pop     es           // restore ES
    pop     ds           // restore DS
  }
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// Line() - This draws a line from a,b to c,d of color col on screne Where //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void Line(int a, int b, int c, int d, int col, word Where) {
 
  int i,u,s,v,d1x,d1y,d2x,d2y,m,n;
 
  u   = c-a;      // x2-x1
  v   = d-b;      // y2-y1
  d1x = sgn(u);   // d1x is the sign of u (x2-x1) (VALUE -1,0,1)
  d1y = sgn(v);   // d1y is the sign of v (y2-y1) (VALUE -1,0,1)
  d2x = sgn(u);   // d2x is the sign of u (x2-x1) (VALUE -1,0,1)
  d2y = 0;
  m   = abs(u);   // m is the distance between x1 and x2
  n   = abs(v);   // n is the distance between y1 and y2
 
  if (m<=n) {     // if the x distance is greater than the y distance
    d2x = 0;
    d2y = sgn(v); // d2y is the sign of v (x2-x1) (VALUE -1,0,1)
    m   = abs(v); // m is the distance between y1 and y2
    n   = abs(u); // n is the distance between x1 and x2
  }
 
  s = m / 2; // s is the m distance (either x or y) divided by 2
 
  for (i=0;i<m+1;i++) { // repeat this loop until it
                 // is = to m (y or x distance)
    Putpixel(a,b,col,Where); // plot a pixel at the original x1, y1
    s += n;                  // add n (dis of x or y) to s (dis of x of y)
    if (s >= m) {            // if s is >= m (distance between y1 and y2)
      s -= m;
      a += d1x;
      b += d1y;
    }
    else {
      a += d2x;
      b += d2y;
    }
  }
 
}
 
 
//--------------------------VIDEO MEMORY FUNCTIONS-------------------------//
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// Cls() - This clears the screen at location Where to color Col           //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void Cls(byte Col, word Where) {
  asm {
    push    es           // save ES
    mov     cx, 32000    // this is our loop counter.  we want to clear
                         //   64000 bytes of memory, so why do we use 32000?
                         //   1 word = 2 bytes, and we are moving a word at
                         //   a time
    mov     es, [Where]  // move address in Where to ES
    xor     di, di       // zero out DI
    mov     al, [Col]    // move color to AL
    mov     ah, al       // move color to AH (Remember, will be moving
                         //   a WORDS, so we need two copies
    rep     stosw        // copy AX to Where and drecrement CX by 1
                         //   until CX equals 0
    pop     es           // restore ES
  }
}
 
/////////////////////////////////////////////////////////////////////////////
//                                                                         //
// Flip() - This copies the entire screen at "source" to destination.      //
//                                                                         //
/////////////////////////////////////////////////////////////////////////////
 
void Flip(word source, word dest) {
  asm {
    push    ds           // save DS
    mov     ax, [dest]   // copy segment of destination to AX
    mov     es, ax       // set ES to point to destination
    mov     ax, [source] // copy segment of source to AX
    mov     ds, ax       // set DS to point to source
    xor     si, si       // zero out SI
    xor     di, di       // zero out DI
    mov     cx, 32000    // set our counter to 32000
    rep     movsw        // move source to destination by words.  decrement
                         //   CX by 1 each time until CX is 0
    pop     ds           // restore DS
  }
}

back2root/archives/denthor/part-08.txt · Dernière modification: 2021/09/18 20:39 de frater