unit RayTr;
{ Everything-independent super ultra ray-tracing
  by Brion Vibber, 12-13-92, based on lots of stuff
  last revised 12-31-92, unless I forget to change this line.
  12-25-92: set for Doubles
  12-31-92: Totally changed to compete with POV-Ray
}
interface

{$N+,E-,G+,X+} { Heck, I'm only going to use it here }

uses Objects; { For TCollection, a super-useful thingy }

const
  MinReal = 5.0e-324;
  MaxReal = 1.7e308;
  DarnSmall = 0.0001;

type
  PUniverse = ^TUniverse;
  PObject3d = ^TObject3d;
  PLightSource = ^TLightSource;
  PPoint3d = ^TPoint3d;
  PRayInfo = ^TRayInfo;
  PTexture = ^TTexture;
  {PPolygon3d = ^TPolygon3d;
  PPolygonList = ^TPolygonList;}

  TPoint3d = object
    x,y,z: Double;
    procedure SetTo(ax,ay,az: Double);
    procedure MakeUnit;
    procedure Cross(v: TPoint3d);
    function Dot(v: TPoint3d): Double;
    procedure Add(v: TPoint3d);
    procedure Sub(v: TPoint3d);
    procedure Scale(s: Double);
    function Length: Double;
    procedure RotateFrom(v: TPoint3d);
    procedure RotateTo(v: TPoint3d);
    procedure RotateX(d: Double);
    procedure RotateY(d: Double);
    procedure RotateZ(d: Double);
    procedure Rotate(x,y,z: Double);
  end;
  TRay = object
    o,d: TPoint3d;
  end;
  TColor = object
    r,g,b,a: Double; { 0 - 1 } { a[lpha] is transparency }
  end;
  TTexture = object(TObject)

  end;

function Power(x,y: Double): Double;
function Log(x,y: Double): Double;
function ArcSin(x: Double): Double;
function ArcCos(x: Double): Double;
function Tan(x: Double): Double;

implementation

procedure MakeTrip(r,g,b: Double; var c: RgbTriple);
begin
  c.r := r; c.g := g; c.b := b;
end;

function Power(x,y: Double): Double;
var
  i: Integer;
  x1: Double;
begin
  {Power := Exp(y * Ln(x));}
  x1 := x;
  for i := 1 to Trunc(y)-1 do
    x1 := x1 * x;
  Power := x;
end;

function Log(x,y: Double): Double;
begin
  Log := Ln(x) / Ln(y);
end;

function ArcSin(x: Double): Double;
begin
  ArcSin := ArcTan(x / Sqrt(1 - (x*x)));
end;

function ArcCos(x: Double): Double;
begin
  ArcCos := ArcTan(Sqrt(1 - Sqr(x)) / x);
end;

function Tan(x: Double): Double;
begin
  Tan := Sin(x) / Cos(x);
end;

procedure TPoint3d.SetTo(ax,ay,az: Double);
begin
  x := ax; y := ay; z := az;
end;

procedure TPoint3d.MakeUnit;
var
  d: Double;
begin
  d := Sqrt(Sqr(x)+Sqr(y)+Sqr(z));
  if d <> 0 then begin
    x := x / d;
    y := y / d;
    z := z / d;
  end;
end;

procedure TPoint3d.Cross(v: TPoint3d);
var
  xa,ya: Double;
begin
  xa := y*v.z - z*v.y;
  ya := z*v.x - x*v.z;
  z := x*v.y - y*v.x;
  x := xa; y := ya;
end;

function TPoint3d.Dot(v: TPoint3d): Double;
begin
  Dot := x*v.x + y*v.y + z*v.z;
end;

procedure TPoint3d.Add(v: TPoint3d);
begin
  x := x + v.x;
  y := y + v.y;
  z := z + v.z;
end;

procedure TPoint3d.Sub(v: TPoint3d);
begin
  x := x - v.x;
  y := y - v.y;
  z := z - v.z;
end;

procedure TPoint3d.Scale(s: Double);
begin
  x := x * s;
  y := y * s;
  z := z * s;
end;

function TPoint3d.Length: Double;
begin
  Length := Sqrt(Sqr(x)+Sqr(y)+Sqr(z));
end;

procedure TPoint3d.RotateFrom(v: TPoint3d);
var
  d,xa,ya,za,cos1,sin1: Double;
begin
  v.MakeUnit;
  d := Sqrt(Sqr(v.y)+Sqr(v.z));
  cos1 := v.z/d; sin1 := v.y/d;
  ya := y*cos1-z*sin1; z := y*sin1+z*cos1; y := ya;
  cos1 := d; sin1 := -v.x;
  za := z*cos1-x*sin1; x := z*sin1+x*cos1; z := za;
end;

procedure TPoint3d.RotateTo(v: TPoint3d);
var
  d,xa,ya,za,cos1,sin1: Double;
begin
  v.MakeUnit;
  d := Sqrt(Sqr(v.y)+Sqr(v.z));
  cos1 := -v.z/d; sin1 := -v.y/d;
  ya := y*cos1-z*sin1; z := y*sin1+z*cos1; y := ya;
  cos1 := -d; sin1 := v.x;
  za := z*cos1-x*sin1; x := z*sin1+x*cos1; z := za;
end;

end.