unit Tri;

interface

uses
  OpenGL,Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs,StdCtrls,ExtCtrls,ComCtrls;

type
  TForm1 = class(TForm)
    Timer1: TTimer;
    procedure FormCreate(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
  private
    { Private declarations }
    angle:single;
    procedure Draw;//Draws an OpenGL scene on request
  public
    { Public declarations }
  end;

var
  Form1: TForm1;


implementation

{$R *.dfm}

function getNormal(p1,p2,p3:TGLArrayf3):TGLArrayf3;
var a,b:TGLArrayf3;
begin
 a[0]:=p2[0]-p1[0]; a[1]:=p2[1]-p1[1]; a[2]:=p2[2]-p1[2];
 b[0]:=p3[0]-p1[0]; b[1]:=p3[1]-p1[1]; b[2]:=p3[2]-p1[2];
 result[0]:=a[1]*b[2]-a[2]*b[1];
 result[1]:=a[2]*b[0]-a[0]*b[2];
 result[2]:=a[0]*b[1]-a[1]*b[0];
end;


procedure setupPixelFormat(DC:HDC);
const
 pfd:TPIXELFORMATDESCRIPTOR = (
	nSize:sizeof(TPIXELFORMATDESCRIPTOR);	// size
	nVersion:1;				// version
	dwFlags:PFD_SUPPORT_OPENGL or PFD_DRAW_TO_WINDOW or
                PFD_DOUBLEBUFFER;		// support double-buffering
	iPixelType:PFD_TYPE_RGBA;		// color type
	cColorBits:24;				// prefered color depth
	cRedBits:0; cRedShift:0;		// color bits (ignored)
        cGreenBits:0;  cGreenShift:0;
        cBlueBits:0; cBlueShift:0;
        cAlphaBits:0;  cAlphaShift:0;   // no alpha buffer
        cAccumBits: 0;
        cAccumRedBits: 0;  		// no accumulation buffer,
        cAccumGreenBits: 0;             // accum bits (ignored)
        cAccumBlueBits: 0;
        cAccumAlphaBits: 0;
	cDepthBits:16;				// depth buffer
	cStencilBits:0;				// no stencil buffer
	cAuxBuffers:0;				// no auxiliary buffers
	iLayerType:PFD_MAIN_PLANE;              // main layer
        bReserved: 0;
    dwLayerMask: 0;
    dwVisibleMask: 0;
    dwDamageMask: 0;                    // no layer, visible, damage masks */
    );
var pixelFormat:integer;
begin
  pixelFormat := ChoosePixelFormat(DC, @pfd);
  if (pixelFormat = 0) then begin
	MessageBox(WindowFromDC(DC), 'ChoosePixelFormat failed.', 'Error',
		MB_ICONERROR or MB_OK);
	exit;
  end;
  if (SetPixelFormat(DC, pixelFormat, @pfd) <> TRUE) then begin
	MessageBox(WindowFromDC(DC), 'SetPixelFormat failed.', 'Error',
		MB_ICONERROR or MB_OK);
	exit;
  end;
end;


procedure GLInit;
const
  light0_position:TGLArrayf4=( -8.0, 8.0, -16.0, 0.0);
  ambient:  TGLArrayf4=( 0.3, 0.3, 0.3, 0.3);
begin
   // set viewing projection */
   glMatrixMode(GL_PROJECTION);
   glFrustum(-0.1, 0.1, -0.1, 0.1, 0.3, 25.0);
   // position viewer */
   glMatrixMode(GL_MODELVIEW);
   glEnable(GL_DEPTH_TEST);
   glEnable(GL_LIGHTING);

    glLightfv(GL_LIGHT0, GL_POSITION, @light0_position);
    glLightfv(GL_LIGHT0, GL_AMBIENT, @ambient);
    glEnable(GL_LIGHT0);
end;


procedure TForm1.FormCreate(Sender: TObject);
var DC:HDC;
    RC:HGLRC;
    i:integer;
begin
 DC:=GetDC(Handle); //Actually, you can use any widowed control here
 SetupPixelFormat(DC);
 RC:=wglCreateContext(DC); //mache das DC als OpenGL Fenster
 wglMakeCurrent(DC, RC); //aktiviere OpenGL Fenster
 GLInit;
end;



procedure TForm1.FormPaint(Sender: TObject);
begin
   Draw;
end;

procedure TForm1.Draw;
const D=1.5;
      H1=D/1.732;
      H2=D*1.732-H1; // D/H = tg(30) = 1/sqrt(3)
      HY=3.0;
const //vertexes
      a1:TGLArrayf3=(-D, 0, -H1);
      a2:TGLArrayf3=(D, 0, -H1);
      a3:TGLArrayf3=(0, 0, H2);
      a4:TGLArrayf3=(0, HY, 0);
var   n1, n2, n3, n4: TGLArrayf3;   //normals
begin
 n1 := getNormal(a1,a3,a2);
 n2 := getNormal(a1,a2,a4);
 n3 := getNormal(a2,a3,a4);
 n4 := getNormal(a3,a1,a4);
 glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT);
 glEnable(GL_NORMALIZE);
 glShadeModel(GL_FLAT);
 glCullFace(GL_BACK);
 glLoadIdentity;
 glTranslatef(0.0, 0.0, -12.0);
 glRotatef(angle, 0.0, 1.0, 0.0);
 glBegin(GL_TRIANGLES);
  glNormal3fv(@n1);
  glVertex3fv(@a1); glVertex3fv(@a2); glVertex3fv(@a3);
  glNormal3fv(@n2);
  glVertex3fv(@a1); glVertex3fv(@a2); glVertex3fv(@a4);
  glNormal3fv(@n3);
  glVertex3fv(@a2); glVertex3fv(@a3); glVertex3fv(@a4);
  glNormal3fv(@n4);
  glVertex3fv(@a3); glVertex3fv(@a1); glVertex3fv(@a4);
 glEnd;
 SwapBuffers(wglGetCurrentDC);
end;



procedure TForm1.Timer1Timer(Sender: TObject);
begin
    angle:=angle+1.0;
    Draw;

end;

end.