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Re: [Gnu3dkit-discuss] GL slang draft

From: Brent Gulanowski
Subject: Re: [Gnu3dkit-discuss] GL slang draft
Date: Thu, 27 Feb 2003 14:49:06 -0500

On Thursday, February 27, 2003, at 12:39 PM, Philippe C.D. Robert wrote:


FYI the GL slang draft has been posted

This is disappointing:

Related OpenGL state is also automatically tracked if used by the shader. A fragment shader cannot change a fragment's x/y position. To support parallelism at the fragment processing level, fragment shaders are written in a way that expresses the computation required for a single fragment, and access to neighboring fragments is not allowed. A fragment shader is free to read multiple values from a single texture, or multiple values from multiple textures. The values computed by the fragment shader are ultimately used to update frame-buffer memory or texture memory, depending on the current OpenGL
state and the OpenGL command that caused the fragments to be generated.

If I understand that correctly, it means that you cannot simulate things like aberrations in a lens or depth of field using the fragment shader. (The latter I see in the OGL PG is to be done with the accumulation buffer.) Or does it mean that you have to do some kind of two-stage process?

It seems to mean that the kinds of filters associated with photoshop, like blurs, swirls, bleeds, and other such things are still not ready for hardware acceleration. I was hoping that visualizers like for iTunes and WinAmp would be able to move their work to the card, but it seems unlikely.

Brent Gulanowski                                address@hidden
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