Shadow maps - trouble with GL_COMPARE_R_TO_TEXTURE

BlitzMax Forums/OpenGL Module/Shadow maps - trouble with GL_COMPARE_R_TO_TEXTURE

Warner

(Posted 2011) [#1]

I'm trying to convert one of the sgi examples on shadow maps to BlitzMax, but I have trouble getting GL_COMPARE_R_TO_TEXTURE to work.
When I leave the R row of the texture matrix empty, it draws the entire shadow map, without filtering it.

It could be just my card, though, all other shadow map samples showed a black screen.

Hopefully there is someone who wants to have a look at it? Code should run without any external mods.
I indicated the line with "-HERE". (all caps)
Without that line, I see a (blockish, but clear) gray shadow on the white ground. With that line added, there is no shadow visible.

SuperStrict

Rem
/*
 * Copyright (c) 1993-2003, Silicon Graphics, Inc.
 * All Rights Reserved
 *
 * Permission To use, copy, modify, And distribute this software For any
 * purpose And without fee is hereby granted, provided that the above
 * copyright notice appear in all copies And that both the copyright
 * notice And this permission notice appear in supporting documentation,
 * And that the name of Silicon Graphics, Inc. Not be used in
 * advertising Or publicity pertaining To distribution of the software
 * without specific, written prior permission.
 *
 * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED To YOU "AS-IS" And
 * WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED Or OTHERWISE,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY Or
 * FITNESS For A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
 * Graphics, INC.  BE LIABLE To YOU Or ANYONE Else For ANY DIRECT,
 * SPECIAL, INCIDENTAL, INDIRECT Or CONSEQUENTIAL DAMAGES OF ANY KIND,
 * Or ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION, LOSS OF
 * PROFIT, LOSS OF USE, SAVINGS Or REVENUE, Or THE CLAIMS OF THIRD
 * PARTIES, WHETHER Or Not SILICON Graphics, INC.  HAS BEEN ADVISED OF
 * THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED And ON ANY THEORY OF
 * LIABILITY, ARISING OUT OF Or IN CONNECTION WITH THE POSSESSION, USE
 * Or PERFORMANCE OF THIS SOFTWARE.
 *
 * US Government Users Restricted Rights 
 * Use, duplication, Or disclosure by the Government is subject To
 * restrictions set forth in FAR 52.227.19(c)(2) Or subparagraph
 * (c)(1)(ii) of the Rights in Technical Data And Computer Software
 * clause at DFARS 252.227-7013 And/Or in similar Or successor clauses
 * in the FAR Or the DOD Or NASA FAR Supplement.  Unpublished - rights
 * reserved under the copyright laws of the United States.
 *
 * Contractor/manufacturer is:
 *	Silicon Graphics, Inc.
 *	1500 Crittenden Lane
 *	Mountain View, CA  94043
 *	United State of America
 *
 * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
 */
 *     shadowmap.c
 *
 */

End Rem

Import brl.GLGraphics

'Include "glutfunc.bmx" 'included below

GLGraphics 800, 600, 0, 60, GRAPHICS_BACKBUFFER | GRAPHICS_DEPTHBUFFER

glewInit()

Const SHADOW_MAP_WIDTH% = 256
Const SHADOW_MAP_HEIGHT% = 256

Const fovy# = 60.0
Const nearPlane# = 10.0
Const farPlane# = 100.0

Global angle# = 0.0
Global torusAngle# = 0.0

Global lightPos:Float[] = [25.0, 25.0, 25.0, 1.0]

Global lookat:Float[] = [0.0, 0.0, 0.0]
Global up:Float[] = [0.0, 0.0, 1.0]

Global white:Float[] = [ 1.0, 1.0, 1.0, 1.0 ]

Global showShadow% = False

init()
reshape(800, 600)

Repeat

	idle()
	display()

Until KeyHit(27)
End


Function init()


    glTexImage2D( GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, ..
  		  SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT, 0, ..
		  GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, Null )
		
    glLightfv( GL_LIGHT0, GL_POSITION, lightPos )
    glLightfv( GL_LIGHT0, GL_SPECULAR, white )
    glLightfv( GL_LIGHT0, GL_DIFFUSE, white )

    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE )
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE )
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR )
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR )
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_GEQUAL )
    glTexParameteri( GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE, GL_LUMINANCE)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_R_TO_TEXTURE)

    glTexGeni( GL_S, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR )
    glTexGeni( GL_T, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR )
    glTexGeni( GL_R, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR )
    glTexGeni( GL_Q, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR )

    glColorMaterial( GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE )

    glCullFace( GL_BACK )

    glEnable( GL_DEPTH_TEST )
    glEnable( GL_LIGHT0 )
    glEnable( GL_LIGHTING )
    glEnable( GL_TEXTURE_2D )
    glEnable( GL_TEXTURE_GEN_S )
    glEnable( GL_TEXTURE_GEN_T )
    glEnable( GL_TEXTURE_GEN_R ) 
    glEnable( GL_TEXTURE_GEN_Q ) 
    glEnable( GL_COLOR_MATERIAL ) 
    glEnable( GL_CULL_FACE ) 
    glDepthFunc(GL_LEQUAL)

End Function

Function reshape( width%, height% )
    glViewport( 0, 0, width, height ) 

    glMatrixMode( GL_PROJECTION ) 
    glLoadIdentity() 
    gluPerspective( fovy, Float(width)/Float(height), nearPlane, farPlane ) 
    glMatrixMode( GL_MODELVIEW ) 
End Function

Function idle()
    angle :+ (KeyDown(39)-KeyDown(37))
    torusAngle :+ 1
End Function

Function transposeMatrix:Float[]( m:Float[] )
    Local r#
    r# = m[1] m[1] = m[4] m[4] = r
    r# = m[2] m[2] = m[8] m[8] = r
    r# = m[3] m[3] = m[12] m[12] = r 
    r# = m[6] m[6] = m[9] m[9] = r
    r# = m[7] m[7] = m[13] m[13] = r
    r# = m[11] m[11] = m[14] m[14] = r
End Function

Function drawObjects( shadowRender%=False )

    Local textureOn% = glIsEnabled( GL_TEXTURE_2D ) 

    If ( shadowRender ) ..
        glDisable( GL_TEXTURE_2D ) 

    If ( Not (shadowRender )  )
        glNormal3f( 0, 0, 1 ) 
        glColor3f( 1, 1, 1 ) 
        glRectf( -20.0, -20.0, 20.0, 20.0 ) 
    End If
    
    glPushMatrix() 
    glTranslatef( 11, 11, 11 ) 
    glRotatef( 54.73, -5, 5, 0 ) 
    glRotatef( torusAngle, 1, 0, 0 ) 
    glColor3f( 1, 0, 0 ) 
    glutSolidTorus( 1, 4, 8, 36 ) 
    glPopMatrix() 

    glPushMatrix() 
    glTranslatef( 2, 2, 2 ) 
    glColor3f( 0, 0, 1 ) 
    glutSolidCube( 4 ) 
    glPopMatrix() 

    glPushMatrix() 
    glTranslatef( lightPos[0], lightPos[1], lightPos[2] ) 
    glColor3f( 1, 1, 1 ) 
'    glutWireSphere( 0.5, 6, 6 ) 
    glPopMatrix() 

    If ( shadowRender  And  textureOn )  ..
        glEnable( GL_TEXTURE_2D ) 

End Function


Function generateShadowMap()

    Local viewport:Int[4] 
    Local lightPos:Float[4] 

    glGetLightfv( GL_LIGHT0, GL_POSITION, Varptr lightPos[0] ) 
    glGetIntegerv( GL_VIEWPORT, Varptr viewport[0] ) 
    glViewport( 0, 0, SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT ) 

    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ) 

    glMatrixMode( GL_PROJECTION ) 
    glPushMatrix() 
    glLoadIdentity() 
    gluPerspective( 80.0, 1.0, 10.0, 1000.0 )

    glMatrixMode( GL_MODELVIEW ) 

    glPushMatrix() 
    glLoadIdentity() 
    gluLookAt( lightPos[0], lightPos[1], lightPos[2], ..
	       lookat[0], lookat[1], lookat[2], ..
	       up[0], up[1], up[2] ) 

    drawObjects( GL_TRUE ) 

    glPopMatrix() 
    glMatrixMode( GL_PROJECTION ) 
    glPopMatrix() 
    glMatrixMode( GL_MODELVIEW ) 

    glCopyTexImage2D( GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, 0, 0, ..
		      SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT, 0 ) 

    glViewport( viewport[0], viewport[1], viewport[2], viewport[3] ) 

    If ( showShadow ) 
      Local depthImage:Float[SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT] 
      glReadPixels( 0, 0, SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT,  ..
		    GL_DEPTH_COMPONENT, GL_FLOAT, depthImage ) 
      glDrawPixels( SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT, GL_LUMINANCE,  ..
		    GL_FLOAT, depthImage ) 
      Flip
    End If

End Function

Function generateTextureMatrix()

    Local tmpMatrix:Float[16] 

    Rem
	/*
     *  Set up projective texture matrix.  We use the GL_MODELVIEW matrix
     *    stack And OpenGL matrix commands To make the matrix.
     */
    End Rem

    glPushMatrix() 
    glLoadIdentity() 
    glTranslatef( 0.5, 0.5, 0.0 ) 
    glScalef( 0.5, 0.5, 1.0 ) 
    gluPerspective( 60.0, 1.0, 1.0, 1000.0 );
    gluLookAt( lightPos[0], lightPos[1], lightPos[2], ..
	       lookat[0], lookat[1], lookat[2], ..
	       up[0], up[1], up[2] ) 
    
    glGetFloatv( GL_MODELVIEW_MATRIX, Varptr tmpMatrix[0] ) 
    glPopMatrix() 

    transposeMatrix( tmpMatrix )

    glTexGenfv( GL_S, GL_OBJECT_PLANE, Varptr tmpMatrix[0])
    glTexGenfv( GL_T, GL_OBJECT_PLANE, Varptr tmpMatrix[4])
'    glTexGenfv( GL_R, GL_OBJECT_PLANE, Varptr tmpMatrix[8])'<-----------------------------------HERE
    glTexGenfv( GL_Q, GL_OBJECT_PLANE, Varptr tmpMatrix[12])

End Function

Function display()

    Local radius# = 30 

    generateShadowMap() 
    generateTextureMatrix() 

    If ( showShadow ) ..
      Return 

    glClearColor( 0, 1, 0, 1 )
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ) 
    glClearColor( 0, 0, 0, 1 )
    
    glPushMatrix() 
    gluLookAt( radius*Cos(angle), radius*Sin(angle), 30, ..
	       lookat[0], lookat[1], lookat[2],  ..
	       up[0], up[1], up[2] )  
    drawObjects( GL_FALSE ) 
    glPopMatrix() 

    Flip

End Function









' --------------------- glutfunc - -------------------- glutfunc -----------------------

Function glutSolidTorus(innerRadius:Float, outerRadius:Float, nsides:Int, rings:Int)
	doughnut(innerRadius, outerRadius, nsides, rings)
End Function

Function doughnut(r:Float, _r:Float, nsides:Int, rings:Int)
  Local i:Int, j:Int;
  Local theta:Float, phi:Float, theta1:Float;
  Local cosTheta:Float, sinTheta:Float;
  Local cosTheta1:Float, sinTheta1:Float;
  Local ringDelta:Float, sideDelta:Float;

  ringDelta = 2.0 * 180 / rings; 'changed from PI to 180degrees because bmax uses degrees in cos/sin
  sideDelta = 2.0 * 180 / nsides;

  theta = 0.0;
  cosTheta = 1.0;
  sinTheta = 0.0;
  For i = rings-1 To 0 Step -1
    theta1 = theta + ringDelta;
    cosTheta1 = Cos(theta1);
    sinTheta1 = Sin(theta1);
    glBegin(GL_QUAD_STRIP);
    phi = 0.0;
    For j = nsides To 0 Step -1
      Local cosPhi:Float, sinPhi:Float, dist:Float;

      phi :+ sideDelta;
      cosPhi = Cos(phi);
      sinPhi = Sin(phi);
      dist = _R + r * cosPhi;

      glNormal3f(cosTheta1 * cosPhi, -sinTheta1 * cosPhi, sinPhi);
      glVertex3f(cosTheta1 * dist, -sinTheta1 * dist, r * sinPhi);
      glNormal3f(cosTheta * cosPhi, -sinTheta * cosPhi, sinPhi);
      glVertex3f(cosTheta * dist, -sinTheta * dist,  r * sinPhi);
    Next
    glEnd();
    theta = theta1;
    cosTheta = cosTheta1;
    sinTheta = sinTheta1;
  Next
End Function



Function drawBox(size:Float, drawStyle:Int )

  Local n:Float[][] =[.. '6*3
    [-1.0, 0.0, 0.0],..
    [0.0, 1.0, 0.0],..
    [1.0, 0.0, 0.0],..
    [0.0, -1.0, 0.0],..
    [0.0, 0.0, 1.0],..
    [0.0, 0.0, -1.0]..
  ];


  Local faces:Float[][] =[.. '6*4
    [0.0, 1.0, 2.0, 3.0],..
    [3.0, 2.0, 6.0, 7.0],..
    [7.0, 6.0, 5.0, 4.0],..
    [4.0, 5.0, 1.0, 0.0],..
    [5.0, 6.0, 2.0, 1.0],..
    [7.0, 4.0, 0.0, 3.0]..
  ];

  Local v:Float[8,3] '8*3
	v[0,0] = -size / 2;
	v[1,0] = -size / 2;
	v[2,0] = -size / 2;
	v[3,0] = -size / 2;
	
	v[4,0] = size / 2;
	v[5,0] = size / 2;
	v[6,0] = size / 2;
	v[7,0] = size / 2;
	
	v[0,1] = -size / 2;
	v[1,1] = -size / 2;
	v[4,1] = -size / 2;
	v[5,1] = -size / 2;
	
	v[7,1] = size / 2;
	v[3,1] = size / 2;
	v[2,1] = size / 2;
	v[6,1] = size / 2;
	
	v[7,2] = -size / 2;
	v[4,2] = -size / 2;
	v[0,2] = -size / 2;
	v[3,2] = -size / 2;
	
	v[6,2] = size / 2;
	v[5,2] = size / 2;
	v[1,2] = size / 2;
	v[2,2] = size / 2;

  For Local i:Int = 5 To 0 Step -1
    glBegin(drawStyle);
    glNormal3fv(Varptr n[i][0] );
    glVertex3fv(Varptr v[faces[i][0],0]);
    glVertex3fv(Varptr v[faces[i][1],0]);
    glVertex3fv(Varptr v[faces[i][2],0]);
    glVertex3fv(Varptr v[faces[i][3],0]);
    glEnd();
  Next
End Function

Function glutSolidCube(size:Double)
	drawBox(size, GL_QUADS)
End Function

Last edited 2011

jkrankie

(Posted 2011) [#2]

Hi,

I'm seeing this on my mac with the line commented out:

and this with it uncommented:

This is on my Mac Mini, which has an Nvidia Gforce 9800 card.

Cheers
Charlie

Warner

(Posted 2011) [#3]

That's just weird. Without the line, I get this:

And with that line, I see this:

I find it troubling that the same code renders something else on two different cards, however, it is reassuring that both not render what it is supposed to render.
I'll start the translation again from scratch. Maybe there is something I am overlooking:

/*
 * Copyright (c) 1993-2003, Silicon Graphics, Inc.
 * All Rights Reserved
 *
 * Permission To use, copy, modify, And distribute this software For any
 * purpose And without fee is hereby granted, provided that the above
 * copyright notice appear in all copies And that both the copyright
 * notice And this permission notice appear in supporting documentation,
 * And that the name of Silicon Graphics, Inc. Not be used in
 * advertising Or publicity pertaining To distribution of the software
 * without specific, written prior permission.
 *
 * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED To YOU "AS-IS" And
 * WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED Or OTHERWISE,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY Or
 * FITNESS For A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
 * Graphics, INC.  BE LIABLE To YOU Or ANYONE Else For ANY DIRECT,
 * SPECIAL, INCIDENTAL, INDIRECT Or CONSEQUENTIAL DAMAGES OF ANY KIND,
 * Or ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION, LOSS OF
 * PROFIT, LOSS OF USE, SAVINGS Or REVENUE, Or THE CLAIMS OF THIRD
 * PARTIES, WHETHER Or Not SILICON Graphics, INC.  HAS BEEN ADVISED OF
 * THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED And ON ANY THEORY OF
 * LIABILITY, ARISING OUT OF Or IN CONNECTION WITH THE POSSESSION, USE
 * Or PERFORMANCE OF THIS SOFTWARE.
 *
 * US Government Users Restricted Rights 
 * Use, duplication, Or disclosure by the Government is subject To
 * restrictions set forth in FAR 52.227.19(c)(2) Or subparagraph
 * (c)(1)(ii) of the Rights in Technical Data And Computer Software
 * clause at DFARS 252.227-7013 And/Or in similar Or successor clauses
 * in the FAR Or the DOD Or NASA FAR Supplement.  Unpublished - rights
 * reserved under the copyright laws of the United States.
 *
 * Contractor/manufacturer is:
 *	Silicon Graphics, Inc.
 *	1500 Crittenden Lane
 *	Mountain View, CA  94043
 *	United State of America
 *
 * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
 */
 *     shadowmap.c
 *
 */

#Include <stdio.h>
#Include <GL/glut.h>
#Include <GL/glext.h>
#Include "helpers.h"

#ifdef GL_ARB_shadow
#define GL_TEXTURE_COMPARE_MODE      GL_TEXTURE_COMPARE_MODE_ARB
#define GL_TEXTURE_COMPARE_FUNC      GL_TEXTURE_COMPARE_FUNC_ARB
#define GL_DEPTH_TEXTURE_MODE        GL_DEPTH_TEXTURE_MODE_ARB
#define GL_COMPARE_R_TO_TEXTURE      GL_COMPARE_R_TO_TEXTURE_ARB
#EndIf

#define SHADOW_MAP_WIDTH      256
#define SHADOW_MAP_HEIGHT     256

#define Pi       3.14159265359

GLdouble    fovy      = 60.0;
GLdouble    nearPlane = 10.0;
GLdouble    farPlane  = 100.0;

GLfloat     angle = 0.0;
GLfloat     torusAngle = 0.0;

GLfloat     lightPos[] = { 25.0, 25.0, 25.0, 1.0 };
GLfloat     lookat[] = { 0.0, 0.0, 0.0 };
GLfloat     up[] = { 0.0, 0.0, 1.0 };

GLboolean showShadow = GL_FALSE;

void
init( void )
{
    GLfloat  white[] = { 1.0, 1.0, 1.0, 1.0 };

    glTexImage2D( GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, 
  		  SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT, 0,
		  GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, Null );

    glLightfv( GL_LIGHT0, GL_POSITION, lightPos );
    glLightfv( GL_LIGHT0, GL_SPECULAR, white );
    glLightfv( GL_LIGHT0, GL_DIFFUSE, white );

    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL );
    glTexParameteri( GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE, GL_LUMINANCE );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE,
		     GL_COMPARE_R_TO_TEXTURE );

    glTexGeni( GL_S, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR );
    glTexGeni( GL_T, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR );
    glTexGeni( GL_R, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR );
    glTexGeni( GL_Q, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR );

    glColorMaterial( GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE );

    glCullFace( GL_BACK );

    glEnable( GL_DEPTH_TEST );
    glEnable( GL_LIGHT0 );
    glEnable( GL_LIGHTING );
    glEnable( GL_TEXTURE_2D );
    glEnable( GL_TEXTURE_GEN_S );
    glEnable( GL_TEXTURE_GEN_T );
    glEnable( GL_TEXTURE_GEN_R );
    glEnable( GL_TEXTURE_GEN_Q );
    glEnable( GL_COLOR_MATERIAL );
    glEnable( GL_CULL_FACE );
}

void
reshape( Int width, Int height )
{
    glViewport( 0, 0, width, height );

    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    gluPerspective( fovy, (GLdouble) width/height, nearPlane, farPlane );
    glMatrixMode( GL_MODELVIEW );
}

void
idle( void )
{
    angle += Pi / 10000;
    torusAngle += .1;
    glutPostRedisplay();
}


void
keyboard( unsigned char key, Int x, Int y )
{
    switch( key ) {
    Case 27:  /* Escape */
      Exit( 0 );
      break;

    Case 't': {
        static GLboolean textureOn = GL_TRUE;
        textureOn = !textureOn;
        If ( textureOn )
	glEnable( GL_TEXTURE_2D );
        Else
	glDisable( GL_TEXTURE_2D );
      }
      break;
      
    Case 'm': {
        static GLboolean compareMode = GL_TRUE;
        compareMode = !compareMode;
        printf( "Compare mode %s\n", compareMode ? "On" : "Off" );
        glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE,
		         compareMode ? GL_COMPARE_R_TO_TEXTURE : GL_NONE );
      }
      break;

    Case 'f': {
        static GLboolean funcMode = GL_TRUE;
        funcMode = !funcMode;
        printf( "Operator %s\n", funcMode ? "GL_LEQUAL" : "GL_GEQUAL" );
        glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC,
		         funcMode ? GL_LEQUAL : GL_GEQUAL );
      }
      break;

    Case 's':
      showShadow = !showShadow;
      break;

    Case 'p': {
        static GLboolean  Animate = GL_TRUE;
        Animate = !Animate;
        glutIdleFunc( Animate ? idle : Null );
      }
      break;
    }

    glutPostRedisplay();
}


void
transposeMatrix( GLfloat m[16] )
{
    GLfloat  tmp;
#define Swap( a, b )    tmp = a; a = b; b = tmp
    Swap( m[1],  m[4]  );
    Swap( m[2],  m[8]  );
    Swap( m[3],  m[12] );
    Swap( m[6],  m[9]  );
    Swap( m[7],  m[13] );
    Swap( m[11], m[14] );
#undef Swap
}

void
drawObjects( GLboolean shadowRender )
{
    GLboolean textureOn = glIsEnabled( GL_TEXTURE_2D );

    If ( shadowRender )
        glDisable( GL_TEXTURE_2D );

    If ( !shadowRender ) {
        glNormal3f( 0, 0, 1 );
        glColor3f( 1, 1, 1 );
        glRectf( -20.0, -20.0, 20.0, 20.0 );
    }
    
    glPushMatrix();
    glTranslatef( 11, 11, 11 );
    glRotatef( 54.73, -5, 5, 0 );
    glRotatef( torusAngle, 1, 0, 0 );
    glColor3f( 1, 0, 0 );
    glutSolidTorus( 1, 4, 8, 36 );
    glPopMatrix();

    glPushMatrix();
    glTranslatef( 2, 2, 2 );
    glColor3f( 0, 0, 1 );
    glutSolidCube( 4 );
    glPopMatrix();

    glPushMatrix();
    glTranslatef( lightPos[0], lightPos[1], lightPos[2] );
    glColor3f( 1, 1, 1 );
    glutWireSphere( 0.5, 6, 6 );
    glPopMatrix();

    If ( shadowRender && textureOn ) 
        glEnable( GL_TEXTURE_2D );
}


void
generateShadowMap( void )
{
    GLint    viewport[4];
    GLfloat  lightPos[4];

    glGetLightfv( GL_LIGHT0, GL_POSITION, lightPos );
    glGetIntegerv( GL_VIEWPORT, viewport );

    glViewport( 0, 0, SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT );

    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

    glMatrixMode( GL_PROJECTION );
    glPushMatrix();
    glLoadIdentity();
    gluPerspective( 80.0, 1.0, 10.0, 1000.0 );
    glMatrixMode( GL_MODELVIEW );

    glPushMatrix();
    glLoadIdentity();
    gluLookAt( lightPos[0], lightPos[1], lightPos[2],
	       lookat[0], lookat[1], lookat[2],
	       up[0], up[1], up[2] );

    drawObjects( GL_TRUE );

    glPopMatrix();
    glMatrixMode( GL_PROJECTION );
    glPopMatrix();
    glMatrixMode( GL_MODELVIEW );

    glCopyTexImage2D( GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, 0, 0,
		      SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT, 0 );

    glViewport( viewport[0], viewport[1], viewport[2], viewport[3] );

    If ( showShadow ) {
      GLfloat depthImage[SHADOW_MAP_WIDTH][SHADOW_MAP_HEIGHT];
      glReadPixels( 0, 0, SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT, 
		    GL_DEPTH_COMPONENT, GL_FLOAT, depthImage );
      glWindowPos2f( viewport[2]/2, 0 );
      glDrawPixels( SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT, GL_LUMINANCE, 
		    GL_FLOAT, depthImage );
      glutSwapBuffers();
    }
}

void
generateTextureMatrix( void )
{
    GLfloat  tmpMatrix[16];

    /*
     *  Set up projective texture matrix.  We use the GL_MODELVIEW matrix
     *    stack And OpenGL matrix commands To make the matrix.
     */
    glPushMatrix();
    glLoadIdentity();
    glTranslatef( 0.5, 0.5, 0.0 );
    glScalef( 0.5, 0.5, 1.0 );
    gluPerspective( 60.0, 1.0, 1.0, 1000.0 );
    gluLookAt( lightPos[0], lightPos[1], lightPos[2],
	       lookat[0], lookat[1], lookat[2],
	       up[0], up[1], up[2] );
    glGetFloatv( GL_MODELVIEW_MATRIX, tmpMatrix );
    glPopMatrix();

    transposeMatrix( tmpMatrix );

    glTexGenfv( GL_S, GL_OBJECT_PLANE, &tmpMatrix[0] );
    glTexGenfv( GL_T, GL_OBJECT_PLANE, &tmpMatrix[4] );
    glTexGenfv( GL_R, GL_OBJECT_PLANE, &tmpMatrix[8] );
    glTexGenfv( GL_Q, GL_OBJECT_PLANE, &tmpMatrix[12] );
}

void
display( void )
{
    GLfloat  radius = 30;

    generateShadowMap();
    generateTextureMatrix();

    If ( showShadow )
      Return;

    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
    
    glPushMatrix();
    gluLookAt( radius*Cos(angle), radius*Sin(angle), 30,
	       lookat[0], lookat[1], lookat[2], 
	       up[0], up[1], up[2] );
    drawObjects( GL_FALSE );
    glPopMatrix();

    glutSwapBuffers();
}

Int
Main( Int argc, char** argv )
{
    glutInit( &argc, argv );
    glutInitDisplayMode( GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE );
    glutInitWindowSize( 512, 512 );
    glutInitWindowPosition( 100, 100 );
    glutCreateWindow( argv[0] );

    init();

    glutDisplayFunc( display );
    glutReshapeFunc( reshape );
    glutKeyboardFunc( keyboard );
    glutIdleFunc( idle );

    glutMainLoop();

    Return 0;
}

jkrankie

(Posted 2011) [#4]

Output is identical on Windows XP with an Nvidia 6800 GT.

The shadow projected from both the box and the torus onto the ground plane looks right, although it's very blocky. Those projected onto the cube and the torus look wrong though, almost as if you've got the texcoords wrong.

Can't think why the shadow texture is inverted on the plane.

Cheers
Charlie

Warner

(Posted 2011) [#5]

I now tried running the C code in DevC++. That seems to work exactly as the BlitzMax version. So, I'm thinking the problem could be in the original sample. That would be weird, since it is a sgi example.
I have trouble understanding the technique, but as I understood, the technique should work as follows:
1. render the scene from the light view
2. store z-buffer in texture
3. adjust texture matrix to match camera view
4. apply texture
5. set 'compare' mode on for z-buffer (compares texture z-buffer and screen z-buffer)
6. render scene again
I may be missing some key steps in this process, though.
In this case, the z-comparisation seems to malfunction in the above program.
But when you disable this, it does show the texture rendered in step 1-4.

Warner

(Posted 2011) [#6]

I just can't get it to work properly. Is there anyone with shadow mapping experience that could give some pointers or possibly an example?

col	(Posted 2011) [#7]

double post. lol

Last edited 2011

col	(Posted 2011) [#8]

Hi Warner.

I get the same result as in Post#2 by jkrankie. I'm more of a DirectX guy but I'll take a look through your code now, no promises though...

Maybe JoshK would be a better person to help you on this? He's well into OpenGL.

Have you checked this tutorial http://www.paulsprojects.net/tutorials/smt/smt.html?? The only reason I suggest this link is he seems to set up the matrices similar to how I did the shadow mapping in the graphics showcase forum.

Sony Vaio VGN-FW31M

Last edited 2011