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Index › Programming Questions & Help › OpenGL and 3D Libraries › floating point textures
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floating point textures (Read 1501 times)
ac
floating point textures
Dec 21st, 2006, 4:54am  
I'm working on a program that does off-screen rendering to a texture using framebuffer objects. If the texture is a regular RGBA with 4 bits per channel, then the performance is ok. But as soon as I try any floating point texture format (GL_FLOAT_RGBA16_NV, GL_RGBA_FLOAT16_ATI, GL_RGBA16F_ARB, etc.) the performance goes down dramatically.

Has anyone tried to use floating point textures with success?

Thanks.
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ac
Re: floating point textures
Reply #1 - Dec 27th, 2006, 6:50pm  
I found a way to solve this problem, and it is using a GLPbuffer for off-screen rendering. The pbuffer has to be properly configured to support floating point textures and 16 bits per channel. The following code is the pbuffer initialization:

Code:

	  int floatBits = 16;
	  int floatAlphaBits = 16;
	  int floatDepthBits = 1; // Workaround for apparent bug when not using render-to-texture-rectangle.

	  GLCapabilities caps = new GLCapabilities();
	  caps.setDoubleBuffered(false);
	  caps.setPbufferFloatingPointBuffers(true);
	  caps.setRedBits(floatBits);
	  caps.setGreenBits(floatBits);
	  caps.setBlueBits(floatBits);
	  caps.setAlphaBits(floatAlphaBits);
	  caps.setDepthBits(floatDepthBits);
	  pBuffer = GLDrawableFactory.getFactory().createGLPbuffer(caps, null, canvasWidth, canvasHeight, GLContext.getCurrent());
	  PainterEventListener listener = new PainterEventListener(painter);
	  pBuffer.addGLEventListener(listener);


In combination with the pbuffer, a GLEventListener is also needed to encapsulate the actual rendering calls. The complete example is available here:
http://shaders.computaciongrafica.com/

It's basically a particle system that runs (almost) entirely on the GPU. The gradient of the luminance is used to determine the motion of the particles.
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ac
Re: floating point textures
Reply #2 - Jan 3rd, 2007, 6:30pm  
The location of the painter program changed, now it is:

http://shaders.computaciongrafica.com/painterly/painterTest2.applet/index.html

It also should have better compatibility with ATI cards.
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