program My_3D;
uses graph,crt;
const max=100;

procedure calc(var x,y,z,xt,yt,zt,xan,yan,zan:real);
begin
  Yt:= Y * COS(Xan) - Z * SIN(Xan);
  Zt:= Y * SIN(Xan) + Z * COS(Xan);
  Y:= Yt;
  Z:= Zt;
  Xt:= X * COS(Yan) - Z * SIN(Xan);
  Zt:= X * SIN(Yan) + Z * COS(Xan);
  X:= Xt;
  Z:= Zt;
  Xt:= X * COS(Zan) - Y * SIN(Zan);
  Yt:= X * SIN(Zan) + Y * COS(Zan);
  X:= Xt;
  Y:= Yt;

end;

var
 gd,gm,i,i1,i2:integer;
  modelx4,modely4,modelz4,modelx1,modely1,modelz1,modelx2,modely2,modelz2,modelx3,
modely3,modelz3:array[1..max] of real;
 xan,yan,zan:real;
 yt,xt,zt:real;
 sx1,sx2,sx3,sx4,sy1,sy2,sy3,sy4,sz1,sz2,sz3,sz4:integer;
 arr: array[1 .. 8] of integer;
 modelfile:text;
 path:string;
 zoom:integer;
 colorbuf:integer;
 color:array[1..max] of integer;
 buf1,buf2,buf3,buf4:real;
 sum1,sum2:real;
 j1,j2,j3,j4,j1a,j2a,j3a,j4a:real;
 page:integer;

begin
writeln('Hello I am 3d engine =)');
writeln('Select model:');
readln(path);
writeln('Let the party begin!');
readln;
gd:=detect;initgraph(gd,gm,'C:\bp\bgi');

xan:=0.02;
yan:=0.02;
zan:=0.02;

zoom:=15;

{path:='cube.dat';}
assign(modelfile,path);
reset(modelfile);
readln(modelfile,i);

for i1:=1 to i do
 begin
   readln(modelfile,color[i1],modelx1[i1],modely1[i1],modelz1[i1],modelx2[i1],model
y2[i1],modelz2[i1],
  modelx3[i1],modely3[i1],modelz3[i1],modelx4[i1],modely4[i1],modelz4[i1]);
 end;

page:=1;

repeat

setcolor(white);
for i1:=1 to i do
 begin
  calc(modelx1[i1],modely1[i1],modelz1[i1],xt,yt,zt,xan,yan,zan);
  calc(modelx2[i1],modely2[i1],modelz2[i1],xt,yt,zt,xan,yan,zan);
  calc(modelx3[i1],modely3[i1],modelz3[i1],xt,yt,zt,xan,yan,zan);
  calc(modelx4[i1],modely4[i1],modelz4[i1],xt,yt,zt,xan,yan,zan);
 end;

for i1:=1 to i-1 do
 for i2:=1 to i-1 do
 begin
  sum1:=modelz1[i1]+modelz2[i1]+modelz3[i1]+modelz4[i1];
  sum2:=modelz1[i1+1]+modelz2[i1+1]+modelz3[i1+1]+modelz4[i1+1];
  if sum1<sum2 then
   begin
    buf1:=modelz1[i1+1];
    buf2:=modelz2[i1+1];
    buf3:=modelz3[i1+1];
    buf4:=modelz4[i1+1];
    modelz1[i1+1]:=modelz1[i1];
    modelz2[i1+1]:=modelz2[i1];
    modelz3[i1+1]:=modelz3[i1];
    modelz4[i1+1]:=modelz4[i1];
    modelz1[i1]:=buf1;
    modelz2[i1]:=buf2;
    modelz3[i1]:=buf3;
    modelz4[i1]:=buf4;

    buf1:=modelx1[i1+1];
    buf2:=modelx2[i1+1];
    buf3:=modelx3[i1+1];
    buf4:=modelx4[i1+1];
    modelx1[i1+1]:=modelx1[i1];
    modelx2[i1+1]:=modelx2[i1];
    modelx3[i1+1]:=modelx3[i1];
    modelx4[i1+1]:=modelx4[i1];
    modelx1[i1]:=buf1;
    modelx2[i1]:=buf2;
    modelx3[i1]:=buf3;
    modelx4[i1]:=buf4;

    buf1:=modely1[i1+1];
    buf2:=modely2[i1+1];
    buf3:=modely3[i1+1];
    buf4:=modely4[i1+1];
    modely1[i1+1]:=modely1[i1];
    modely2[i1+1]:=modely2[i1];
    modely3[i1+1]:=modely3[i1];
    modely4[i1+1]:=modely4[i1];
    modely1[i1]:=buf1;
    modely2[i1]:=buf2;
    modely3[i1]:=buf3;
    modely4[i1]:=buf4;

    colorbuf:=color[i1+1];
    color[i1+1]:=color[i1];
    color[i1]:=colorbuf;
   end;
 end;

setactivepage(page);               <-- вот тут я это и делаю 
if page=1 then page:=2
else page:=1;
setvisualpage(page);

for i1:=2 to i do
 begin
  sx1:=round(zoom*modelx1[i1])+320;
  sy1:=round(zoom*modely1[i1])+240;
  sx2:=round(zoom*modelx2[i1])+320;
  sy2:=round(zoom*modely2[i1])+240;
  sx3:=round(zoom*modelx3[i1])+320;
  sy3:=round(zoom*modely3[i1])+240;
  sx4:=round(zoom*modelx4[i1])+320;
  sy4:=round(zoom*modely4[i1])+240;
  line(sx1,sy1,sx2,sy2);
  line(sx2,sy2,sx3,sy3);
  line(sx3,sy3,sx4,sy4);
  line(sx4,sy4,sx1,sy1);
  arr[1]:=sx1;
  arr[2]:=sy1;
  arr[3]:=sx2;
  arr[4]:=sy2;
  arr[5]:=sx3;
  arr[6]:=sy3;
  arr[7]:=sx4;
  arr[8]:=sy4;
  setfillstyle(1,color[i1]);
  fillpoly(4,arr);
 end;

delay(15000);
cleardevice;

until keypressed;
closegraph;
end.