Light Volume

OpenGL OpenGL: Advanced Coding
1

Im playing around will light volume and they look great… the only thing is I can’t get rid of a 1px (or something) artifact around it… Im sure it comes from my stencil test code… I try to fiddle with it but can’t get rid of these artifacts… does anyone have an idea??? or can point me a better technique than the one Im using? tks in advance!


		...
		...
		...

		glDepthMask( GL_FALSE );
		
		glColorMask( GL_FALSE,
					 GL_FALSE,
					 GL_FALSE,
					 GL_FALSE );
		
		glEnable( GL_DEPTH_TEST );
		glEnable( GL_STENCIL_TEST );		
		
		glClearStencil( 0 );
		glClear( GL_STENCIL_BUFFER_BIT );
		glEnable( GL_CULL_FACE );

		

		glCullFace( GL_FRONT );
		glDepthFunc( GL_GREATER );		
		glStencilFunc( GL_ALWAYS, 1, 1 );
		glStencilOp( GL_KEEP, GL_REPLACE, GL_KEEP );
		
		render_light_volume( tmp );
		
		
		
		glCullFace( GL_BACK );
		glStencilOp( GL_KEEP, GL_KEEP, GL_REPLACE );
		
		render_light_volume( tmp );
		
		

		glColorMask( GL_TRUE,
					 GL_TRUE,
					 GL_TRUE,
					 GL_TRUE );
		
		glDepthFunc( GL_ALWAYS );
		glStencilFunc( GL_NOTEQUAL, 1, 1 );
		glStencilOp( GL_KEEP, GL_KEEP, GL_KEEP );
		
		glDisable( GL_CULL_FACE );

		render_light_volume( tmp );

		glEnable( GL_CULL_FACE );
		glDisable( GL_STENCIL_TEST );		
		glCullFace( GL_BACK );
		glDepthFunc( GL_LEQUAL );
		glDepthMask( GL_TRUE );

		...
		...
		...
2

What exactly is that code supposed to do? Most code which marks something within the stencil (whether it is a shadow volume or pixels influenced by the light) uses the GL_INCR and GL_DECR stencil operations.

3

yes, perhaps a more complete example is in order…

4

Im implementing the example of deferred shading example of the more opengl programming book… however Im trying to tweak it a little cuz I think their approach is a bit too generic… I make the whole thing work except that artifact on the light volume that I can seems to be capable to fix… :frowning:

That’s why any help would be appreciated! :slight_smile:

5

How the artifact looks like? You can use the GLIntercept to check if the stencil buffer contains expected content.

6

Light volumes are kindof same as shadow volumes but handled differently.
You using stencil pass or fail method?