Using a depth buffer as a texture

OpenGL Development JOGL Development
#1

Hi

What’s the best way to use a (texture configured as a) depth buffer as an actual texture? Preferably without having to write a shader!

I tried just binding and using, but I get a uniform grey rectangle.

Cheers

IA

#2

I use a depth texture attached to the depth attachment of a framebuffer object directly as a texture in my app, and it works.
Make sure you’re disabling GL_TEXTURE_COMPARE_MODE if it’s used as a shadowmap normally.

Maybe show us the faulty code?

#3 

            GL gl = view.getGL ();
            GLU glu = view.getGLU ();
            
        /* 2D setup */
            gl.glPushAttrib( GL_ALL_ATTRIB_BITS );
            gl.glPushClientAttrib( (int)GL_CLIENT_ALL_ATTRIB_BITS );
            gl.glDisable( GL_LIGHTING );
            gl.glDisable( GL_DEPTH_TEST );
            gl.glDepthMask( false );
            gl.glMatrixMode( GL_PROJECTION );
            gl.glPushMatrix();
            gl.glLoadIdentity();
            
            int width = view.getDrawable().getWidth();
            int height = view.getDrawable().getHeight();
            glu.gluOrtho2D( 0, width, 0, height );
            gl.glEnable( GL_TEXTURE_2D );
            
            gl.glMatrixMode( GL_MODELVIEW );
            gl.glPushMatrix();
            gl.glLoadIdentity(); 
            gl.glDisable( GL_TEXTURE_COMPARE_MODE );
                        
        /* Render */
            int depthBufferID = frameBuffer.getDepthBufferID();
            gl.glBindTexture( GL_TEXTURE_2D, depthBufferID );
            gl.glBegin( GL_QUADS );
            //gl.glColor3f( 1.0f, 0.0f, 0.0f );
            gl.glTexCoord2f( 0.0f, 0.0f );
            gl.glVertex2f( 0, 0 );
            //gl.glColor3f( 0.0f, 1.0f, 0.0f );
            gl.glTexCoord2f( 1.0f, 0.0f );
            gl.glVertex2f( 256, 0 );
            //gl.glColor3f( 0.0f, 0.0f, 1.0f );
            gl.glTexCoord2f( 1.0f, 1.0f );
            gl.glVertex2f( 256, 256 );
            //gl.glColor3f( 1.0f, 1.0f, 0.0f );
            gl.glTexCoord2f( 0.0f, 1.0f );
            gl.glVertex2f( 0, 256 );
            gl.glEnd();
            
        /* 2D teardown */
            gl.glMatrixMode( GL_PROJECTION );
            gl.glPopMatrix();
            gl.glMatrixMode( GL_MODELVIEW );
            gl.glPopMatrix();
            gl.glDepthMask( true );
            gl.glEnable( GL_DEPTH_TEST );            
            gl.glPopClientAttrib();
            gl.glPopAttrib();
#4

I don’t think glDisable will work here. Here’s what I use :
gl.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_COMPARE_MODE, GL.GL_NONE);

Also a “gl.glColor4f(1, 1, 1, 1);” might help.

#5

Bah, I went ahead and wrote a CG shader, which was an education for me. Works nicely now (though I’d still like to know what was missing from the above ??? )