3D Solids

                    嬪様様様様様様様様様様様様様様様
                             W E L C O M E         
                      To the VGA Trainer Program    
                                  By                
                          DENTHOR of ASPHYXIA        
                    塒様様様様様様様様様様様様様様様  
                      陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳 
                        陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳

                            --==[ PART 9 ]==--

 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
  Introduction

 Hi there! ASPHYXIA is BACK with our first MegaDemo, Psycho Neurosis! A
 paltry 1.3MB download is all it takes to see the group from Durbs first
 major production! We are quite proud of it, and think you should see it
 ;)

 Secondly, I released a small little trainer (a trainerette ;-)) on
 RsaPROG and Connexctix BBS mail, also on the ASPHYXIA BBS as COPPERS.ZIP
 It is a small Pascal program demonstrating how to display copper bars in
 text mode. Also includes a check for horizontal retrace (A lot of people
 wanted it, that is why I wrote the program) (ASPHYXIA ... first with the
 trainer goodies ;-)  aargh, sorry, had to be done ))

 Thirdly, sorry about the problems with Tut 8! If you had all the
 checking on, the tutorial would probably die on the first points. The
 reason is this : in the first loop, we have DrawPoints then
 RotatePoints. The variables used in DrawPoints are set in RotatePoints,
 so if you put RotatePoints before DrawPoints, the program should work
 fine. Alternatively, turn off error checking 8-)

 Fourthly, I have had a surprisingly large number of people saying that
 "I get this, like, strange '286 instructions not enabled' message!
 What's wrong with your code, dude?"  To all of you, get into Pascal, hit
 Alt-O (for options), hit enter and a 2 (for Enable 286 instructions). Hard
 hey? Doesn't anyone EVER set up their version of Pascal?

 Now, on to todays tutorial! 3D solids. That is what the people wanted,
 that is what the people get! This tutorial is mainly on how to draw the
 polygon on screen. For details on how the 3D stuff works, check out tut
 8.

 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 to Denthor, EzE or Goth on Connectix.
             3) Write to :  Grant Smith
                            P.O.Box 270 Kloof
                            3640
                            Natal
             4) Call me (Grant Smith) at (031) 73 2129 (leave a message if you
                   call during varsity)
             5) 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!

 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
  How to draw a polygon

 Sounds easy enough, right? WRONG! There are many, many different ways to
 go about this, and today I'll only be showing you one. Please don't take
 what is written here as anything approaching the best method, it is just
 here to get you on your way...

 The procedure I will be using here is based on something most of us
 learned in standard eight ... I think. I seem to recall doing something
 like this in Mrs. Reids maths class all those years ago ;)

 Take two points, x1,y1 and x2,y2. Draw them :

                   + (x1,y1)
                    \
                      \  <-- Point a somewhere along the line
                        \
                          + (x2,y2)

 Right, so what we have to do is this : if we know the y-coord of a, what
 is it's x-coord? To prove the method we will give the points random
 values.

                  + (2,10)
                   \
                     \  <-- a.y = 12
                       \
                         +  (15,30)

 Right. Simple enough problem. This is how we do it :
    (a.y-y1) = (12 - 10)  {to get a.y as though y1 was zero}
    *(x2-x1) = *(15 - 2)  {the total x-length of the line}
    /(y2-y1) = /(30 - 10) {the total y-length of the line}
         +x1 = +2         { to get the equation back to real coords}

 So our equation is :  (a.y-y1)*(x2-x1)/(y2-y1)+x4    or
                       (12-10)*(15-2)/(30-10)+2
       which gives you :
                       2*13/20+2 = 26/20+2
                                 = 3.3

 That means that along the line with y=12, x is equal to 3.3. Since we
 are not concerned with the decimal place, we replace the  /  with a div,
 which in Pascal gives us an integer result, and is faster too. All well
 and good, I hear you cry, but what does this have to do with life and
 how it relates to polygons in general. The answer is simple. For each of
 the four sides of the polygon we do the above test for each y line. We
 store the smallest and the largest x values into separate variables for
 each line, and draw a horizontal line between them. Ta-Dah! We have a
 cool polygon!

 For example : Two lines going down :

                 +             +
                / <-x1     x2->|   <--For this y line
              /                |
            +                  +

 Find x1 and x2 for that y, then draw a line between them. Repeat for all
 y values.

 Of course, it's not as simple as that. We have to make sure we only
 check those y lines that contain the polygon (a simple min y, max y test
 for all the points). We also have to check that the line we are
 calculating actually extends as far as where our current y is (check
 that the point is between both y's). We have to compare each x to see
 weather it is smaller then the minimum x value so far, or bigger then
 the maximum (the original x min is set as a high number, and the x max
 is set as a small number). We must also check that we only draw to the
 place that we can see ( 0-319 on the x ; 0-199 on the y (the size of the
 MCGA screen))

 To see how this looks in practice, have a look at the sample code
 provided. (Mrs. Reid would probably kill me for the above explanation,
 so when you learn it in school, split it up into thousands of smaller
 equations to get the same answer ;))

 Okay, that's it! What's that? How do you draw a vertical line? Thats
 simple ...

 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
  Drawing a vertical line

 Right, this is a lot easier than drawing a normal line (Tut 5 .. I
 think), because you stay on the same y value. So, what you do is you set
 ES to the screen you want to write to, and get DI to the start of the
 y-line (see earlier trainers for a description of how SEGMENT:OFFSET
 works.

 IN   : x1 , x2, y, color, where

            asm
              mov    ax,where
              mov    es,ax
              mov    di,y
              mov    ax,y
              shl    di,8   { di:=di*256 }
              shl    ax,6   { ax:=ax*64 }
              add    di,ax  { di := (y*256)+(y*64) := y*320 Faster then a
                              straight multiplication }

 Right, now you add the first x value to get your startoff.
              add    di,x1
 Move the color to store into ah and al
              mov    al,color
              mov    ah,al       { ah:=al:=color }
 then get CX equal to how many pixels across you want to go
              mov    cx,x2
              sub    cx,x1   { cx:=x2-x1 }
 Okay, as we all know, moving a word is a lot faster then moving a byte,
 so we halve CX
              shr    cx,1    { cx:=cx/2 }
 but what happens if CX was an odd number. After a shift, the value of
 the last number is placed in the carry flag, so what we do is jump over
 a single byte move if the carry flag is zero, or execute it if it is
 one.
             jnc     @Start  { If there is no carry, jump to label Start }
             stosb           { ES:[DI]:=al ; increment DI }
         @Start :            { Label Start }
             rep     stosw   { ES:[DI]:=ax ; DI:=DI+2; repeat CX times }

 Right, the finished product looks like this :

 Procedure Hline (x1,x2,y:word;col:byte;where:word); assembler;
   { This draws a horizontal line from x1 to x2 on line y in color col }
 asm
   mov   ax,where
   mov   es,ax
   mov   ax,y
   mov   di,ax
   shl   ax,8
   shl   di,6
   add   di,ax
   add   di,x1

   mov   al,col
   mov   ah,al
   mov   cx,x2
   sub   cx,x1
   shr   cx,1
   jnc   @start
   stosb
 @Start :
   rep   stosw
 end;

 Done!

 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
   In closing

 This 3D system is still not perfect. It needs to be faster, and now I
 have also dumped the problem of face-sorting on you! Nyahahahaha!

            [ My sister and I were driving along the other day when she
                asked me, what would I like for my computer.
              I thought long and hard about it, and came up with the
                following hypothesis. When a girl gets a Barbie doll, she
                then wants the extra ballgown for the doll, then the
                hairbrush, and the car, and the house, and the friends
                etc.
              When a guy gets a computer, he wants the extra memory, the
                bigger hard drive, the maths co-pro, the better
                motherboard, the latest software, and the bigger monitor
                etc.
              I told my sister all of this, and finished up with : "So as
                you can see, computers are Barbie dolls for MEN!"
              She called me a chauvinist. And hit me. Hard.
                                                                    ]
                                                        - Grant Smith
                                                            19:24
                                                              26/2/94

 See you next time!
   - Denthor

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

 浜様様様様様様様様様様様様曜様様様様様様様様僕様様僕様僕様曜様様
 BBS Name                  Telephone No.   Open MsgFilePast
 麺様様様様様様様様様様様様洋様様様様様様様様陵様様陵様陵様洋様様
 ASPHYXIA BBS #1           (031) 765-5312  ALL   *  *   *  
 ASPHYXIA BBS #2           (031) 765-6293  ALL   *  *   *  
 Connectix BBS             (031) 266-9992  ALL      *   *  
 藩様様様様様様様様様様様様擁様様様様様様様様瞥様様瞥様瞥様擁様様

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

 Does no other BBS's ANYWHERE carry the trainer? Am I writing this for
 three people who get it from one of these BBS's each week? Should I go
 on? (Hehehehe ... I was pleased to note that Tut 8 was THE most
 downloaded file from ASPHYXIA BBS last month ... )

 {$X+}
 USES Crt;

 CONST VGA = $A000;
       maxpolys = 5;
       A : Array [1..maxpolys,1..4,1..3] of integer =
         (
          ((-10,10,0),(-2,-10,0),(0,-10,0),(-5,10,0)),
          ((10,10,0),(2,-10,0),(0,-10,0),(5,10,0)),
          ((-2,-10,0),(2,-10,0),(2,-5,0),(-2,-5,0)),
          ((-6,0,0),(6,0,0),(7,5,0),(-7,5,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0))
         );  { The 3-D coordinates of our object ... stored as (X1,Y1,Z1), }
             { (X2,Y2,Z2) ... for the 4 points of a poly }
      S : Array [1..maxpolys,1..4,1..3] of integer =
         (
          ((-10,-10,0),(10,-10,0),(10,-7,0),(-10,-7,0)),
          ((-10,10,0),(10,10,0),(10,7,0),(-10,7,0)),
          ((-10,1,0),(10,1,0),(10,-2,0),(-10,-2,0)),
          ((-10,-8,0),(-7,-8,0),(-7,0,0),(-10,0,0)),
          ((10,8,0),(7,8,0),(7,0,0),(10,0,0))
         );  { The 3-D coordinates of our object ... stored as (X1,Y1,Z1), }
             { (X2,Y2,Z2) ... for the 4 points of a poly }
      P : Array [1..maxpolys,1..4,1..3] of integer =
         (
          ((-10,-10,0),(-7,-10,0),(-7,10,0),(-10,10,0)),
          ((10,-10,0),(7,-10,0),(7,0,0),(10,0,0)),
          ((-9,-10,0),(9,-10,0),(9,-7,0),(-9,-7,0)),
          ((-9,-1,0),(9,-1,0),(9,2,0),(-9,2,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0))
         );  { The 3-D coordinates of our object ... stored as (X1,Y1,Z1), }
             { (X2,Y2,Z2) ... for the 4 points of a poly }
      H : Array [1..maxpolys,1..4,1..3] of integer =
         (
          ((-10,-10,0),(-7,-10,0),(-7,10,0),(-10,10,0)),
          ((10,-10,0),(7,-10,0),(7,10,0),(10,10,0)),
          ((-9,-1,0),(9,-1,0),(9,2,0),(-9,2,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0))
         );  { The 3-D coordinates of our object ... stored as (X1,Y1,Z1), }
             { (X2,Y2,Z2) ... for the 4 points of a poly }
      Y : Array [1..maxpolys,1..4,1..3] of integer =
         (
          ((-7,-10,0),(0,-3,0),(0,0,0),(-10,-7,0)),
          ((7,-10,0),(0,-3,0),(0,0,0),(10,-7,0)),
          ((-2,-3,0),(2,-3,0),(2,10,0),(-2,10,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0))
         );  { The 3-D coordinates of our object ... stored as (X1,Y1,Z1), }
             { (X2,Y2,Z2) ... for the 4 points of a poly }
      X : Array [1..maxpolys,1..4,1..3] of integer =
         (
          ((-7,-10,0),(10,7,0),(7,10,0),(-10,-7,0)),
          ((7,-10,0),(-10,7,0),(-7,10,0),(10,-7,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0))
         );  { The 3-D coordinates of our object ... stored as (X1,Y1,Z1), }
             { (X2,Y2,Z2) ... for the 4 points of a poly }
      I : Array [1..maxpolys,1..4,1..3] of integer =
         (
          ((-10,-10,0),(10,-10,0),(10,-7,0),(-10,-7,0)),
          ((-10,10,0),(10,10,0),(10,7,0),(-10,7,0)),
          ((-2,-9,0),(2,-9,0),(2,9,0),(-2,9,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0)),
          ((0,0,0),(0,0,0),(0,0,0),(0,0,0))
         );  { The 3-D coordinates of our object ... stored as (X1,Y1,Z1), }
             { (X2,Y2,Z2) ... for the 4 points of a poly }

 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..maxpolys,1..4] of Point;  { The base object rotated }
     Translated : Array [1..maxpolys,1..4] 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}

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 Procedure SetMCGA;  { This procedure gets you into 320x200x256 mode. }
 BEGIN
   asm
      mov        ax,0013h
      int        10h
   end;
 END;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 Procedure SetText;  { This procedure returns you to text mode.  }
 BEGIN
   asm
      mov        ax,0003h
      int        10h
   end;
 END;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 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;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 Procedure SetUpVirtual;
    { This sets up the memory needed for the virtual screen }
 BEGIN
   GetMem (VirScr,64000);
   vaddr := seg (virscr^);
 END;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 Procedure ShutDown;
    { This frees the memory used by the virtual screen }
 BEGIN
   FreeMem (VirScr,64000);
 END;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 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;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 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;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 Procedure Hline (x1,x2,y:word;col:byte;where:word); assembler;
   { This draws a horizontal line from x1 to x2 on line y in color col }
 asm
   mov   ax,where
   mov   es,ax
   mov   ax,y
   mov   di,ax
   shl   ax,8
   shl   di,6
   add   di,ax
   add   di,x1

   mov   al,col
   mov   ah,al
   mov   cx,x2
   sub   cx,x1
   shr   cx,1
   jnc   @start
   stosb
 @Start :
   rep   stosw
 end;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 Procedure DrawPoly(x1,y1,x2,y2,x3,y3,x4,y4:integer;color:byte;where:word);
   { This draw a polygon with 4 points at x1,y1 , x2,y2 , x3,y3 , x4,y4
     in color col }
 var
   x:integer;
   mny,mxy:integer;
   mnx,mxx,yc:integer;
   mul1,div1,
   mul2,div2,
   mul3,div3,
   mul4,div4:integer;

 begin
   mny:=y1; mxy:=y1;
   if y2mxy then mxy:=y2;
   if y3mxy then mxy:=y3;    { Choose the min y mny and max y mxy }
   if y4mxy then mxy:=y4;

   if mny<0 then mny:=0;
   if mxy>199 then mxy:=199;
   if mny>199 then exit;
   if mxy<0 then exit;        { Verticle range checking }

   mul1:=x1-x4; div1:=y1-y4;
   mul2:=x2-x1; div2:=y2-y1;
   mul3:=x3-x2; div3:=y3-y2;
   mul4:=x4-x3; div4:=y4-y3;  { Constansts needed for intersection calc }

   for yc:=mny to mxy do
     begin
       mnx:=320;
       mxx:=-1;
       if (y4>=yc) or (y1>=yc) then
         if (y4<=yc) or (y1<=yc) then   { Check that yc is between y1 and y4 }
           if not(y4=y1) then
             begin
               x:=(yc-y4)*mul1 div div1+x4; { Point of intersection on x axis }
               if xmxx then
                 mxx:=x;       { Set point as start or end of horiz line }
             end;
       if (y1>=yc) or (y2>=yc) then
         if (y1<=yc) or (y2<=yc) then   { Check that yc is between y1 and y2 }
           if not(y1=y2) then
             begin
               x:=(yc-y1)*mul2 div div2+x1; { Point of intersection on x axis }
               if xmxx then
                 mxx:=x;       { Set point as start or end of horiz line }
             end;
       if (y2>=yc) or (y3>=yc) then
         if (y2<=yc) or (y3<=yc) then   { Check that yc is between y2 and y3 }
           if not(y2=y3) then
             begin
               x:=(yc-y2)*mul3 div div3+x2; { Point of intersection on x axis }
               if xmxx then
                 mxx:=x;       { Set point as start or end of horiz line }
             end;
       if (y3>=yc) or (y4>=yc) then
         if (y3<=yc) or (y4<=yc) then   { Check that yc is between y3 and y4 }
           if not(y3=y4) then
             begin
               x:=(yc-y3)*mul4 div div4+x3; { Point of intersection on x axis }
               if xmxx then
                 mxx:=x;       { Set point as start or end of horiz line }
             end;
       if mnx<0 then
         mnx:=0;
       if mxx>319 then
         mxx:=319;          { Range checking on horizontal line }
       if mnx<=mxx then
         hline (mnx,mxx,yc,color,where);   { Draw the horizontal line }
     end;
   end;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 Function rad (theta : real) : real;
   {  This calculates the degrees of an angle }
 BEGIN
   rad := theta * pi / 180
 END;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 Procedure SetUpPoints;
   { This creates the lookup table }
 VAR loop1,loop2:integer;
 BEGIN
   For loop1:=0 to 360 do BEGIN
     lookup [loop1,1]:=sin (rad (loop1));
     lookup [loop1,2]:=cos (rad (loop1));
   END;
 END;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 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;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 Procedure RotatePoints (X,Y,Z:Integer);
   { This rotates object lines by X,Y and Z; then places the result in
     TRANSLATED }
 VAR loop1,loop2:integer;
     temp:point;
 BEGIN
   For loop1:=1 to maxpolys do BEGIN
     For loop2:=1 to 4 do BEGIN
       temp.x:=lines[loop1,loop2].x;
       temp.y:=lookup[x,2]*lines[loop1,loop2].y - lookup[x,1]*lines[loop1,loop2].z;
       temp.z:=lookup[x,1]*lines[loop1,loop2].y + lookup[x,2]*lines[loop1,loop2].z;

       translated[loop1,loop2]:=temp;

       If y>0 then BEGIN
         temp.x:=lookup[y,2]*translated[loop1,loop2].x - lookup[y,1]*translated[loop1,loop2].y;
         temp.y:=lookup[y,1]*translated[loop1,loop2].x + lookup[y,2]*translated[loop1,loop2].y;
         temp.z:=translated[loop1,loop2].z;
         translated[loop1,loop2]:=temp;
       END;

       If z>0 then BEGIN
         temp.x:=lookup[z,2]*translated[loop1,loop2].x + lookup[z,1]*translated[loop1,loop2].z;
         temp.y:=translated[loop1,loop2].y;
         temp.z:=-lookup[z,1]*translated[loop1,loop2].x + lookup[z,2]*translated[loop1,loop2].z;
         translated[loop1,loop2]:=temp;
       END;
     END;
   END;
 END;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 Procedure DrawPoints;
   { This draws the translated object to the virtual screen }
 VAR loop1:Integer;
     nx,ny,nx2,ny2,nx3,ny3,nx4,ny4:integer;
     temp:integer;
 BEGIN
   For loop1:=1 to maxpolys do BEGIN
     If (translated[loop1,1].z+zoff<0) and (translated[loop1,2].z+zoff<0) and
        (translated[loop1,3].z+zoff<0) and (translated[loop1,4].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;
       temp:=round (translated[loop1,3].z+zoff);
       nx3:=round (256*translated[loop1,3].X) div temp+xoff;
       ny3:=round (256*translated[loop1,3].Y) div temp+yoff;
       temp:=round (translated[loop1,4].z+zoff);
       nx4:=round (256*translated[loop1,4].X) div temp+xoff;
       ny4:=round (256*translated[loop1,4].Y) div temp+yoff;
       drawpoly (nx,ny,nx2,ny2,nx3,ny3,nx4,ny4,13,vaddr);
     END;
   END;
 END;

 {陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳}
 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,loop2:integer;
     ch:char;

   Procedure Whizz (sub:boolean);
   VAR loop1:integer;
   BEGIN
     For loop1:=-64 to -5 do BEGIN
       zoff:=loop1*8;
       if sub then xoff:=xoff-7 else xoff:=xoff+7;
       RotatePoints (deg,deg,deg);
       DrawPoints;
       flip (vaddr,vga);
       Cls (vaddr,0);
       deg:=(deg+5) mod 360;
     END;
   END;

 BEGIN
   deg:=0;
   ch:=#0;
   Yoff:=100;
   Xoff:=350;
   Cls (vaddr,0);
   For loop1:=1 to maxpolys do
     For loop2:=1 to 4 do BEGIN
       Lines [loop1,loop2].x:=a [loop1,loop2,1];
       Lines [loop1,loop2].y:=a [loop1,loop2,2];
       Lines [loop1,loop2].z:=a [loop1,loop2,3];
     END;
   Whizz (TRUE);

   For loop1:=1 to maxpolys do
     For loop2:=1 to 4 do BEGIN
       Lines [loop1,loop2].x:=s [loop1,loop2,1];
       Lines [loop1,loop2].y:=s [loop1,loop2,2];
       Lines [loop1,loop2].z:=s [loop1,loop2,3];
     END;
   Whizz (FALSE);

   For loop1:=1 to maxpolys do
     For loop2:=1 to 4 do BEGIN
       Lines [loop1,loop2].x:=p [loop1,loop2,1];
       Lines [loop1,loop2].y:=p [loop1,loop2,2];
       Lines [loop1,loop2].z:=p [loop1,loop2,3];
     END;
   Whizz (TRUE);

   For loop1:=1 to maxpolys do
     For loop2:=1 to 4 do BEGIN
       Lines [loop1,loop2].x:=h [loop1,loop2,1];
       Lines [loop1,loop2].y:=h [loop1,loop2,2];
       Lines [loop1,loop2].z:=h [loop1,loop2,3];
     END;
   Whizz (FALSE);

   For loop1:=1 to maxpolys do
     For loop2:=1 to 4 do BEGIN
       Lines [loop1,loop2].x:=y [loop1,loop2,1];
       Lines [loop1,loop2].y:=y [loop1,loop2,2];
       Lines [loop1,loop2].z:=y [loop1,loop2,3];
     END;
   Whizz (TRUE);

   For loop1:=1 to maxpolys do
     For loop2:=1 to 4 do BEGIN
       Lines [loop1,loop2].x:=x [loop1,loop2,1];
       Lines [loop1,loop2].y:=x [loop1,loop2,2];
       Lines [loop1,loop2].z:=x [loop1,loop2,3];
     END;
   Whizz (FALSE);

   For loop1:=1 to maxpolys do
     For loop2:=1 to 4 do BEGIN
       Lines [loop1,loop2].x:=i [loop1,loop2,1];
       Lines [loop1,loop2].y:=i [loop1,loop2,2];
       Lines [loop1,loop2].z:=i [loop1,loop2,3];
     END;
   Whizz (TRUE);

   For loop1:=1 to maxpolys do
     For loop2:=1 to 4 do BEGIN
       Lines [loop1,loop2].x:=a [loop1,loop2,1];
       Lines [loop1,loop2].y:=a [loop1,loop2,2];
       Lines [loop1,loop2].z:=a [loop1,loop2,3];
     END;
   Whizz (FALSE);

   cls (vaddr,0);
   cls (vga,0);
   Xoff := 160;

   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);
     cls (vaddr,0);
     RotatePoints (deg,deg,deg);
     deg:=(deg+5) mod 360;
   Until ch=#27;
 END;

 BEGIN
   SetUpVirtual;
   clrscr;
   Writeln ('Hello there! Varsity has begun once again, so it is once again');
   Writeln ('back to the grindstone ;-) ... anyway, this tutorial is, by');
   Writeln ('popular demand, on poly-filling, in relation to 3-D solids.');
   Writeln;
   Writeln ('In this program, the letters of ASPHYXIA will fly past you. As you');
   Writeln ('will see, they are solid, not wireframe. After the last letter has');
   Writeln ('flown by, a large A will be left in the middle of the screen.');
   Writeln;
   Writeln ('You will be able to move it around the screen, and you will notice');
   Writeln ('that it may have bits only half on the screen, i.e. clipping is');
   Writeln ('perfomed. To control it use the following : "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 ('I hope this is what you wanted...leave me mail for new ideas.');
   writeln;
   writeln;
   Write ('  Hit any key to contine ...');
   Readkey;
   SetMCGA;
   SetUpPoints;
   MoveAround;
   SetText;
   ShutDown;
   Writeln ('All done. This concludes the ninth 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 ('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.

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Date this article was posted to GameDev.net: 7/16/1999
(Note that this date does not necessarily correspond to the date the article was written)

See Also:
Denthor's Asphyxia Tutorials

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