First it's a square, then a butterfly? and then finally a star field
flying by
lazarus / 39-Graphics

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TBMan · 2025-04-18 18:13

I eventually got to the star field I wanted...   lmao

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
starfielddemo; uses  ptccrt,  ptcgraph,sysutils;  const  MaxStars =
200;  Type    VideoPages = (Page0, Page1);   IchangeType = record    
 xc,yc:double;  end;   IArrayType = array[0..360] of IChangeType;  
StarType = record    xposition,yposition,    xc,yc:double;   
color:integer;  end; var  InertiaTable:IArrayType;  Page: VideoPages =
Page0;  gdriver,gmode:smallint;  Index:integer;  RightLStars, 
LeftLStars,  RightUStars,  LeftUstars:array[0..MaxStars] of
startype;   {***************** Page flipping**************}  procedure
Nextactivepage;  begin    if page = page0 then page := page1    else 
   page := page0;      SetactivePage(Ord(Page));  end; procedure
NextVisualPage;  begin    SetVisualpage(Ord(Page));  end; {*********
 Timer ****************************} procedure
frametick2(Milliseconds:integer);var  scount,ecount:qword;begin 
scount := getTickCount64;  repeat    ecount := gettickcount64;  until
ecount > scount+Milliseconds;end; {*************  Inertia Table
*******************}Procedure BuildInertiaTable; const   
CoordIncrement = 0.01111111111; var   index:integer;   Xchange, 
 Ychange,   Xaccum,   YAccum:double
;beginfillchar(InertiaTable,sizeof(InertiaTable),0);// ? is this
needed?Ychange :=  CoordIncrement; YAccum := -1;InertiaTable[0].yc :=
-1.0;Inertiatable[360].yc := -1.0;InertiaTable[0].xc :=
0;Inertiatable[360].xc := 0;Xaccum := 0;xchange := -CoordIncrement;//
build portion  to 90 degrees left the yc decreases to 0 , x builds up
to -1for index := 359 downto 270 dobegin   inertiatable[index].yc :=
YAccum;   inertiatable[index].xc := XAccum;   Xaccum :=
Xaccum+Xchange;   YAccum := YAccum+Ychange;end; // now y will increase
to 1 and x will increase to 0;Ychange := CoordIncrement;xchange :=
CoordIncrement;xaccum := -1.0;Yaccum :=  0.0;for index := 269 downto
180 dobegin   inertiatable[index].yc := YAccum; 
 inertiatable[index].xc := XAccum;   Yaccum := Yaccum+ychange; 
 Xaccum := Xaccum+xchange; end; Yaccum := 1;Xaccum := 0;Xchange :=
CoordIncrement;YChange := -CoordIncrement; // now y will decrease from
1 to 0 and x will increase from 0 to 1;for index := 179 downto 90
dobegin   inertiatable[index].yc := YAccum;   inertiatable[index].xc
:= XAccum;   Yaccum := Yaccum+ychange;   Xaccum :=
Xaccum+xchange;end; // now y will decrease from 0 to -1 and x will
decrease from 1 to 0; Xaccum := 1;Yaccum := 0;Xchange :=
-coordincrement;Ychange := -coordincrement; for index := 89 downto 0
dobegin   inertiatable[index].yc := YAccum;   inertiatable[index].xc
:= XAccum;   Yaccum := Yaccum+ychange;   Xaccum :=
Xaccum+xchange; end; end; { *************  Make initial "stars"
****************} procedure seedStars;var  d :integer; 
i:integer;begin   // do left upper quad   for i := 1 to MaxStars do 
 begin      d := random(90)+270;      with LeftUstars[i] do          
begin               xposition := 400;               yposition := 300; 
             xc := inertiatable[d].xc;               yc :=
inertiatable[d].yc;               color :=random(18)+1;           
end;   end;   // upper right    for i := 1 to MaxStars do   begin    
    d := random(90);      with RightUstars[i] do            begin    
         xposition := 400;               yposition := 300;           
  xc := inertiatable[d].xc;               yc := inertiatable[d].yc;  
           color :=random(18)+1;            end;   end;// lower
left for i := 1 to MaxStars do   begin          d := random(90)+180; 
   with LeftLstars[i] do            begin               xposition :=
400;               yposition := 300;               xc :=
inertiatable[d].xc;               yc := inertiatable[d].yc;          
   color := random(18)+1;            end;   end;  //lower right for i
:= 1 to MaxStars do   begin          d := random(90)+90;      with
RightLstars[i] do            begin               xposition := 400;   
          yposition := 300;               xc := inertiatable[d].xc;  
           yc := inertiatable[d].yc;               color
:=random(18)+1;            end;   end; end; {**********  Animate the
stars **************} procedure AnimateStars(i:integer); begin   with
LeftUstars[i] do        begin         
putpixel(round(xposition),round(Yposition),color);          xposition
:= xposition+xc;          yposition := yposition+yc;          if
(xposition <=0) or (Yposition <=0) then             begin           
 xposition := 400;             yposition := 300;             end;    
  end;    with RightUstars[i] do        begin         
putpixel(round(xposition),round(Yposition),color);          xposition
:= xposition+xc;          yposition := yposition+yc;          if
(xposition >=getmaxx) or (Yposition <=0) then             begin      
     xposition := 400;             yposition := 300;             end; 
      end;   with LeftLstars[i] do        begin         
putpixel(round(xposition),round(Yposition),color);          xposition
:= xposition+xc;          yposition := yposition+yc;          if
(xposition <0 ) or (Yposition >=getmaxy) then             begin      
     xposition := 400;             yposition := 300;            
 end;        end;   with RightLstars[i] do        begin         
putpixel(round(xposition),round(Yposition),color);          xposition
:= xposition+xc;          yposition := yposition+yc;          if
(xposition >getmaxx ) or (Yposition >=getmaxy) then             begin 
           xposition := 400;             yposition := 300;           
 end;        end; end; begin   gdriver := vesa;   // uses two video
pages   Gmode := installusermode(800, 600, 256, 2, 8000, 6000); 
WindowTitle := 'StarField';  initgraph(gdriver, gmode, '');  
BuildInertiatable;  randomize;  SeedStars; repeat  nextactivepage; 
clearviewport;   for index := 0 to maxstars do animateStars(index); 
 nextvisualpage;   frametick2(10);until keypressed;; Closegraph; end.