//------------------------------------------------------------------------
//
// Author              : Dario Corno (rIo) / Jeff Molofee (NeHe)
// Converted to Delphi : Jan Horn
// Email               : jhorn@global.co.za
// Website             : http://www.sulaco.co.za
// Authors Web Site    : http://www.spinningkids.org/rio
// Date                : 14 October 2001
// Version             : 1.0
// Description         : Radial Blur
//
// Adapted to FPC      : Sebastian Guenther (sg@freepascal.org) 2001-11-21
//
//------------------------------------------------------------------------
program RadialBlur;

{$mode objfpc}

uses GL, GLU, GLUT;

const
  WND_TITLE = 'Radial Blur';

type TVector = Array[0..2] of glFloat;
var
  ElapsedTime : Integer;             // Elapsed time between frames

  // Textures
  BlurTexture : glUint;              // An Unsigned Int To Store The Texture Number

  // User vaiables
  Angle : glFloat;
  Vertexes : Array[0..3] of TVector;
  normal : TVector;

const
  FPSCount : Integer = 0;            // Counter for FPS
  // Lights and Materials
  globalAmbient  : Array[0..3] of glFloat = (0.2, 0.2,  0.2, 1.0);	// Set Ambient Lighting To Fairly Dark Light (No Color)
  Light0Pos      : Array[0..3] of glFloat = (0.0, 5.0, 10.0, 1.0); 	// Set The Light Position
  Light0Ambient  : Array[0..3] of glFloat = (0.2, 0.2,  0.2, 1.0);	// More Ambient Light
  Light0Diffuse  : Array[0..3] of glFloat = (0.3, 0.3,  0.3, 1.0); 	// Set The Diffuse Light A Bit Brighter
  Light0Specular : Array[0..3] of glFloat = (0.8, 0.8,  0.8, 1.0);      // Fairly Bright Specular Lighting

  LmodelAmbient  : Array[0..3] of glFloat = (0.2, 0.2,  0.2, 1.0); 	// And More Ambient Light


function EmptyTexture : glUint;
var txtnumber : glUint;
    pData : Pointer;
begin
  // Create Storage Space For Texture Data (128x128x4)
  GetMem(pData, 128*128*4);

  glGenTextures(1, @txtnumber);		      		// Create 1 Texture
  glBindTexture(GL_TEXTURE_2D, txtnumber);    		// Bind The Texture
  glTexImage2D(GL_TEXTURE_2D, 0, 4, 128, 128, 0, GL_RGBA, GL_UNSIGNED_BYTE, pData);
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);

  result :=txtNumber;
end;


procedure ReduceToUnit(var vector : Array of glFloat);
var length : glFLoat;
begin
  // Calculates The Length Of The Vector
  length := sqrt((vector[0]*vector[0]) + (vector[1]*vector[1]) + (vector[2]*vector[2]));
  if Length = 0 then
    Length :=1;

  vector[0] :=vector[0] / length;
  vector[1] :=vector[1] / length;
  vector[2] :=vector[2] / length;
end;


procedure calcNormal(const v : Array of TVector; var cross : Array of glFloat);
var v1, v2 : Array[0..2] of glFloat;
begin
  // Finds The Vector Between 2 Points By Subtracting
  // The x,y,z Coordinates From One Point To Another.

  // Calculate The Vector From Point 1 To Point 0
  v1[0] := v[0][0] - v[1][0];	      		// Vector 1.x=Vertex[0].x-Vertex[1].x
  v1[1] := v[0][1] - v[1][1];	      		// Vector 1.y=Vertex[0].y-Vertex[1].y
  v1[2] := v[0][2] - v[1][2];	      		// Vector 1.z=Vertex[0].y-Vertex[1].z
  // Calculate The Vector From Point 2 To Point 1
  v2[0] := v[1][0] - v[2][0];	      		// Vector 2.x=Vertex[0].x-Vertex[1].x
  v2[1] := v[1][1] - v[2][1];	      		// Vector 2.y=Vertex[0].y-Vertex[1].y
  v2[2] := v[1][2] - v[2][2];	      		// Vector 2.z=Vertex[0].z-Vertex[1].z
  // Compute The Cross Product To Give Us A Surface Normal
  cross[0] := v1[1]*v2[2] - v1[2]*v2[1];      	// Cross Product For Y - Z
  cross[1] := v1[2]*v2[0] - v1[0]*v2[2];      	// Cross Product For X - Z
  cross[2] := v1[0]*v2[1] - v1[1]*v2[0];      	// Cross Product For X - Y

  ReduceToUnit(cross);	 			// Normalize The Vectors
end;


// Draws A Helix
procedure ProcessHelix;
const Twists = 5;
      MaterialColor : Array[1..4] of glFloat = (0.4, 0.2, 0.8, 1.0);
      Specular      : Array[1..4] of glFloat = (1, 1, 1, 1);
var x, y, z : glFLoat;
    phi, theta : Integer;
    r, u, v : glFLoat;
begin
  glLoadIdentity();				// Reset The Modelview Matrix
  gluLookAt(0, 5, 50, 0, 0, 0, 0, 1, 0);	// Eye Position (0,5,50) Center Of Scene (0,0,0), Up On Y Axis

  glPushMatrix();				// Push The Modelview Matrix
    glTranslatef(0,0,-50);		        // Translate 50 Units Into The Screen
    glRotatef(angle/2.0, 1, 0, 0);		// Rotate By angle/2 On The X-Axis
    glRotatef(angle/3.0, 0, 1, 0);		// Rotate By angle/3 On The Y-Axis

    glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, @MaterialColor);
    glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, @specular);

    r :=1.5;					// Radius

    glBegin(GL_QUADS);				// Begin Drawing Quads
      phi :=0;
      while phi < 360 do
      begin
        theta :=0;
        while theta < 360*twists do
        begin
          v := phi / 180.0 * pi;  		// Calculate Angle Of First Point	(  0 )
          u := theta / 180.0 * pi; 		// Calculate Angle Of First Point	(  0 )

          x :=cos(u)*(2 + cos(v))*r;		// Calculate x Position (1st Point)
          y :=sin(u)*(2 + cos(v))*r;		// Calculate y Position (1st Point)
          z :=(u-(2*pi) + sin(v))*r;		// Calculate z Position (1st Point)

          vertexes[0][0] :=x;			// Set x Value Of First Vertex
          vertexes[0][1] :=y;			// Set y Value Of First Vertex
          vertexes[0][2] :=z;			// Set z Value Of First Vertex

          v :=(phi/180.0 * pi);	  		// Calculate Angle Of Second Point	(  0 )
          u :=((theta+20)/180.0 * pi);		// Calculate Angle Of Second Point	( 20 )

          x :=cos(u)*(2 + cos(v))*r;		// Calculate x Position (2nd Point)
          y :=sin(u)*(2 + cos(v))*r;		// Calculate y Position (2nd Point)
          z :=(u-(2*pi) + sin(v))*r;		// Calculate z Position (2nd Point)

          vertexes[1][0] :=x;	      		// Set x Value Of Second Vertex
          vertexes[1][1] :=y;	                // Set y Value Of Second Vertex
          vertexes[1][2] :=z;			// Set z Value Of Second Vertex

          v :=(phi+20)/180.0*pi;		// Calculate Angle Of Third Point	( 20 )
          u :=(theta+20)/180.0*pi;		// Calculate Angle Of Third Point	( 20 )

          x :=cos(u)*(2 + cos(v))*r;		// Calculate x Position (3rd Point)
          y :=sin(u)*(2 + cos(v))*r;		// Calculate y Position (3rd Point)
          z :=(u-(2*pi) + sin(v))*r;		// Calculate z Position (3rd Point)

          vertexes[2][0] :=x;			// Set x Value Of Third Vertex
          vertexes[2][1] :=y;			// Set y Value Of Third Vertex
          vertexes[2][2] :=z;			// Set z Value Of Third Vertex

          v :=(phi+20)/180.0*pi;     		// Calculate Angle Of Fourth Point	( 20 )
          u :=theta / 180.0*pi;	     		// Calculate Angle Of Fourth Point	(  0 )

          x :=cos(u)*(2 + cos(v))*r;   		// Calculate x Position (4th Point)
          y :=sin(u)*(2 + cos(v))*r;   		// Calculate y Position (4th Point)
          z :=(u-(2*pi) + sin(v))*r;		// Calculate z Position (4th Point)

          vertexes[3][0] :=x;	    		// Set x Value Of Fourth Vertex
          vertexes[3][1] :=y;	    		// Set y Value Of Fourth Vertex
          vertexes[3][2] :=z;	    		// Set z Value Of Fourth Vertex

          calcNormal(vertexes, normal);	  	// Calculate The Quad Normal

          glNormal3f(normal[0],normal[1],normal[2]);	// Set The Normal

          // Render The Quad
          glVertex3f(vertexes[0][0],vertexes[0][1],vertexes[0][2]);
          glVertex3f(vertexes[1][0],vertexes[1][1],vertexes[1][2]);
          glVertex3f(vertexes[2][0],vertexes[2][1],vertexes[2][2]);
          glVertex3f(vertexes[3][0],vertexes[3][1],vertexes[3][2]);
          theta := theta + 20;
        end;
        phi :=phi + 20;
      end;
    glEnd();				       // Done Rendering Quads
  glPopMatrix();			       // Pop The Matrix
end;


// Set Up An Ortho View
procedure ViewOrtho;
begin
  glMatrixMode(GL_PROJECTION);		   	// Select Projection
  glPushMatrix();			   	// Push The Matrix
  glLoadIdentity();			   	// Reset The Matrix
  glOrtho( 0, 640 , 480 , 0, -1, 1 );	   	// Select Ortho Mode (640x480)
  glMatrixMode(GL_MODELVIEW);		   	// Select Modelview Matrix
  glPushMatrix();			   	// Push The Matrix
  glLoadIdentity();			   	// Reset The Matrix
end;


// Set Up A Perspective View
procedure ViewPerspective;
begin
  glMatrixMode( GL_PROJECTION );	   	// Select Projection
  glPopMatrix();			   	// Pop The Matrix
  glMatrixMode( GL_MODELVIEW );		   	// Select Modelview
  glPopMatrix();    			        // Pop The Matrix
end;


// Renders To A Texture
procedure RenderToTexture;
begin
  glViewport(0, 0, 128, 128);                      	// Set Our Viewport (Match Texture Size)
  ProcessHelix();   					// Render The Helix
  glBindTexture(GL_TEXTURE_2D,BlurTexture);		// Bind To The Blur Texture

  // Copy Our ViewPort To The Blur Texture (From 0,0 To 128,128... No Border)
  glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, 0, 0, 128, 128, 0);
  glClearColor(0.0, 0.0, 0.5, 0.5);			// Set The Clear Color To Medium Blue
  glClear(GL_COLOR_BUFFER_BIT OR GL_DEPTH_BUFFER_BIT);	// Clear The Screen And Depth Buffer
  glViewport(0, 0, 640 ,480);				// Set Viewport (0,0 to 640x480)
end;


// Draw The Blurred Image
procedure DrawBlur(const times : Integer; const inc : glFloat);
var spost, alpha, alphainc : glFloat;
    I : Integer;
begin
  alpha := 0.2;

  glEnable(GL_TEXTURE_2D);		   	// Enable 2D Texture Mapping
  glDisable(GL_DEPTH_TEST);		   	// Disable Depth Testing
  glBlendFunc(GL_SRC_ALPHA,GL_ONE);	   	// Set Blending Mode
  glEnable(GL_BLEND);			   	// Enable Blending
  glBindTexture(GL_TEXTURE_2D,BlurTexture);	// Bind To The Blur Texture
  ViewOrtho();				   	// Switch To An Ortho View

  alphainc := alpha / times;		   	// alphainc=0.2f / Times To Render Blur

  glBegin(GL_QUADS);			   	// Begin Drawing Quads
    // Number Of Times To Render Blur
    For I :=0 to times-1 do
    begin
      glColor4f(1.0, 1.0, 1.0, alpha);	        // Set The Alpha Value (Starts At 0.2)
      glTexCoord2f(0+spost,1-spost);		// Texture Coordinate	( 0, 1 )
      glVertex2f(0,0);		              	// First Vertex		(   0,   0 )

      glTexCoord2f(0+spost,0+spost);		// Texture Coordinate	( 0, 0 )
      glVertex2f(0,480);			// Second Vertex	(   0, 480 )

      glTexCoord2f(1-spost,0+spost);		// Texture Coordinate	( 1, 0 )
      glVertex2f(640,480);			// Third Vertex		( 640, 480 )

      glTexCoord2f(1-spost,1-spost);		// Texture Coordinate	( 1, 1 )
      glVertex2f(640,0);			// Fourth Vertex	( 640,   0 )

      spost := spost + inc; 			// Gradually Increase spost (Zooming Closer To Texture Center)
      alpha := alpha - alphainc;		// Gradually Decrease alpha (Gradually Fading Image Out)
    end;
  glEnd();					// Done Drawing Quads

  ViewPerspective();				// Switch To A Perspective View

  glEnable(GL_DEPTH_TEST);			// Enable Depth Testing
  glDisable(GL_TEXTURE_2D);			// Disable 2D Texture Mapping
  glDisable(GL_BLEND);				// Disable Blending
  glBindTexture(GL_TEXTURE_2D,0);		// Unbind The Blur Texture
end;

{------------------------------------------------------------------}
{  Function to draw the actual scene                               }
{------------------------------------------------------------------}
procedure glDraw;
begin
  glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT);    // Clear The Screen And The Depth Buffer
  glLoadIdentity();                     // Reset The View
  RenderToTexture; 			// Render To A Texture
  ProcessHelix;    			// Draw Our Helix
  DrawBlur(25, 0.02);			// Draw The Blur Effect

  angle :=ElapsedTime / 5.0;   		// Update angle Based On The Clock
end;


{------------------------------------------------------------------}
{  Initialise OpenGL                                               }
{------------------------------------------------------------------}
procedure glInit;
begin
  glClearColor(0.0, 0.0, 0.0, 0.5); 	   // Black Background
  glShadeModel(GL_SMOOTH);                 // Enables Smooth Color Shading
  glClearDepth(1.0);                       // Depth Buffer Setup
  glDepthFunc(GL_LESS);		           // The Type Of Depth Test To Do

  glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);   //Realy Nice perspective calculations

  glEnable(GL_DEPTH_TEST);                 // Enable Depth Buffer
  glEnable(GL_TEXTURE_2D);                 // Enable Texture Mapping

  glLightModelfv(GL_LIGHT_MODEL_AMBIENT, @LmodelAmbient);       // Set The Ambient Light Model

  glLightModelfv(GL_LIGHT_MODEL_AMBIENT, @GlobalAmbient);     	// Set The Global Ambient Light Model
  glLightfv(GL_LIGHT0, GL_POSITION, @light0Pos);	      	// Set The Lights Position
  glLightfv(GL_LIGHT0, GL_AMBIENT, @light0Ambient);	      	// Set The Ambient Light
  glLightfv(GL_LIGHT0, GL_DIFFUSE, @light0Diffuse);	      	// Set The Diffuse Light
  glLightfv(GL_LIGHT0, GL_SPECULAR, @light0Specular);	      	// Set Up Specular Lighting
  glEnable(GL_LIGHTING);										// Enable Lighting
  glEnable(GL_LIGHT0);										// Enable Light0

  BlurTexture := EmptyTexture();								// Create Our Empty Texture
  glShadeModel(GL_SMOOTH);									// Select Smooth Shading
  glMateriali(GL_FRONT, GL_SHININESS, 128);
end;


{------------------------------------------------------------------}
{  Handle window resize                                            }
{------------------------------------------------------------------}
procedure glResizeWnd(Width, Height : Integer);
begin
  if (Height = 0) then                // prevent divide by zero exception
    Height := 1;
  glViewport(0, 0, Width, Height);    // Set the viewport for the OpenGL window
  glMatrixMode(GL_PROJECTION);        // Change Matrix Mode to Projection
  glLoadIdentity();                   // Reset View
  gluPerspective(45.0, Width/glFloat(Height), 2.0, 200.0);  // Do the perspective calculations. Last value = max clipping depth

  glMatrixMode(GL_MODELVIEW);         // Return to the modelview matrix
  glLoadIdentity();                   // Reset View
end;


var
  DemoStart, LastTime : LongWord;


procedure DisplayWindow; cdecl;
begin
  Inc(FPSCount);                      // Increment FPS Counter

  LastTime :=ElapsedTime;
  ElapsedTime := glutGet(GLUT_ELAPSED_TIME) - DemoStart;     // Calculate Elapsed Time
  ElapsedTime :=(LastTime + ElapsedTime) DIV 2; // Average it out for smoother movement
  glDraw;
  glutSwapBuffers;
  Inc(ElapsedTime, 10);
  glutPostRedisplay;
end;

procedure OnReshape(width, height: Integer); cdecl;
begin
  glResizeWnd(width, height);
end;


begin
  glutInit(@argc, argv);
  glutInitDisplayMode(GLUT_RGB or GLUT_DOUBLE or GLUT_DEPTH);
  glutCreateWindow(WND_TITLE);
  glutDisplayFunc(@DisplayWindow);
  glutReshapeFunc(@OnReshape);
  glutInitWindowSize(640, 480);

  glInit;

  DemoStart := glutGet(GLUT_ELAPSED_TIME);
  glutMainLoop;
end.