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type
  float=extended;

  PPoint3DF=^TPoint3DF;
  TPoint3DF=record
    x, y, z: single;
  end;

  PPointCL=^TPointCL;
  TPointCL=record
    x, y, z: extended; //Treffkoordinate der Wand
    ck:byte; //Wo Kollision stattgefunden hat (ob X-, Y- oder Z-Wand)
  end;
  TPointCLArray=array of TPointCL;

...

function QFrac(q:extended):extended;
begin
  if q>=0then result:=Frac(q)else result:=1-Frac(-q);
end;

function QInt(q:extended):extended;
begin
  //if q>=0then result:=Floor(q)else result:=Ceil(q);
  result:=abs(floor(q));
  if q<0then result:=floor(-1-result);
end;

function QSgn(q:extended):shortint;
begin
  result:=0;
  if q<0then result:=-1;
  if q>0then result:=1;
end;

function ESgn(q:extended):shortint;
begin
  result:=0;
  if q>=0then result:=1;
end;

function EqSgn(q,r:extended):shortint;
begin
  result:=0;
  if q>=0then result:=1-result;
  if r>=0then result:=1-result;
//  if q>=0then result:=result or 1;
//  if r>=0then result:=result or 1;
end;

function CalculateCollision(start,stop:TPoint3DF;var output:TPointCLArray): integer;
var
  i:integer;r:byte;
  xs,ys,zs,q:extended;
  xp,yp,zp:extended;
  qx,qy,qz:extended;
  qd:extended;
  p:TPointCL;
begin
  if (Length(output)=0) then begin
    result:=0;
    exit;
  end;
  i:=0;
  xs:=stop.x - start.x;
  ys:=stop.y - start.y;
  zs:=stop.z - start.z;
  q:=0;
  qd:=((Abs(xs)+Abs(ys)+Abs(zs))*1000);
  if qd=0 then qd:=1 else qd:=1/qd;
  while i<length(output) do begin
    q:=q+qd;
    //Find grid position
    xp:=start.x+xs*q;
    yp:=start.y+ys*q;
    zp:=start.z+zs*q;
    if xs=0then qx:=high(integer)else qx:=(QInt(xp)+1*ESgn(xs)-start.x)/xs;
    if ys=0then qy:=high(integer)else qy:=(QInt(yp)+1*ESgn(ys)-start.y)/ys;
    if zs=0then qz:=high(integer)else qz:=(QInt(zp)+1*ESgn(zs)-start.z)/zs;
    if(qx<=qy)and(qx<=qz)then begin
      q:=qx;r:=1;
      if q>1 then break;
      p.x:=start.x+xs*q;
      p.y:=start.y+ys*q;
      p.z:=start.z+zs*q;
      p.ck:=r;output[i]:=p;Inc(i);
      if i>=length(output) then Continue;
      if (Frac(p.y)=0) and (ys<>0) then begin
        p.ck:=2;output[i]:=p;Inc(i);
        if i>=length(output) then Continue;
      end;
      if (Frac(p.z)=0) and (zs<>0) then begin
        p.ck:=3;output[i]:=p;Inc(i);
        if i>=length(output) then Continue;
      end;
      Continue;
    end;
    if(qy<=qx)and(qy<=qz)then begin
      q:=qy;r:=2;
      if q>1 then break;
      p.x:=start.x+xs*q;
      p.y:=start.y+ys*q;
      p.z:=start.z+zs*q;
      p.ck:=r;output[i]:=p;Inc(i);
      if i>=length(output) then Continue;
      if (Frac(p.x)=0) and (xs<>0) then begin
        p.ck:=1;output[i]:=p;Inc(i);
        if i>=length(output) then Continue;
      end;
      if (Frac(p.z)=0) and (zs<>0) then begin
        p.ck:=3;output[i]:=p;Inc(i);
        if i>=length(output) then Continue;
      end;
      Continue;
    end;
    if(qz<=qx)and(qz<=qy)then begin
      q:=qz;r:=3;
      if q>1 then break;
      p.x:=start.x+xs*q;
      p.y:=start.y+ys*q;
      p.z:=start.z+zs*q;
      p.ck:=r;output[i]:=p;Inc(i);
      if i>=length(output) then Continue;
      if (Frac(p.x)=0) and (xs<>0) then begin
        p.ck:=1;output[i]:=p;Inc(i);
        if i>=length(output) then Continue;
      end;
      if (Frac(p.y)=0) and (ys<>0) then begin
        p.ck:=2;output[i]:=p;Inc(i);
        if i>=length(output) then Continue;
      end;
      Continue;
    end;
  end;
  result:=i;