Michel DÃnzer wrote:
On Thu, 2005-03-03 at 20:22 +0100, Roland Scheidegger wrote:
Michel DÃnzer wrote:
On Wed, 2005-03-02 at 16:11 +0100, Marcello Maggioni wrote:
When using HW TCL in Tuxracer or PPRacer (that is essentially the same game) with my Radeon 8500 with DRI drivers dated 25 february 2005 you can see that there are problems with light reflection in those places where there's ice (for example in the first stage that is full of ice pools ) .
You mean the flickering? That's probably Z fighting, most likely a problem in the game itself. You should bring this up with the PPRacer project, now that there's active development there...
No, this is a result of the tcl fallback used for the GL_SPHERE_MAP texgen (it is z fighting I guess).
Sure, but Brian told me the application has to be prepared for and deal with this.
Really? Interesting. What does it have to do? I never really understood what exactly caused the z-fighting issues with the fallbacks.
One of the appendices of the OpenGL Programming Guide discusses invariance. The basic idea is that certain kinds of OpenGL state changes should not result in any difference in the final rasterization, in terms of fragment x,y,z and/or color. For example, changing GL_DEPTH_FUNC from GL_LESS to GL_GEQUAL should have no effect on the generated fragments.
In other cases, a stage change such as enabling/disabling texgen may require that the OpenGL implementation use totally different vertex processing paths (hardware vs. software, perhaps) and the set of fragments generated will be different. That's allowable.
The application programmer has to be aware of this if they're relying on some sort of repeatability.
That said, I don't know exactly what Tuxracer is doing.
-Brian
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