   Cat4.2 and OpenGL
  ATI have released there latest drivers and with it the final extension missing from 1.5 (well, according to the OpenGL Extension viewer) GL_Ext_Shadow_Func I''m also wondering if they have made any fixes to the GLSL stuff, such as the errors pointed out in the ATI GLSL Implimentation thread 
  The GLSL bugs I noticed should be fixed, according to the devrel guy I emailed. It''s too bad I rewrote my shaders in Cg .  ;  hehe, score one for backing up ;  oh I''ve still got the old shaders, but they''re not finished and I''ve changed loads of code since then, so they wouldn''t be compatible without lots of effort. In a couple of months, once the drivers are more or less stable, I might convert them over. Still, at the moment, I really can''t see any advantage over Cg.  ;  ah, fair play, would have been nice to know for def but i understand ya more inclind to do what ya need and not keep stuff ''hanging around'' incase it was needed and to an extent ya right, certainly without the Nvidia implimentation its currently not a fantasic option...  ;quote:Original post by benjamin bunny  oh I''ve still got the old shaders, but they''re not finished and I''ve changed loads of code since then, so they wouldn''t be compatible without lots of effort. In a couple of months, once the drivers are more or less stable, I might convert them over. Still, at the moment, I really can''t see any advantage over Cg.    The advantage that GLSL has is in the optimizations that Cg makes.  Specifically, Cg optimizes shader code for minimum register usage, often at the expense of higher instruction counts.  GeforceFXs benefit from this as the performance hit for using more registers is much higher than for increased instructions, but the same is not true for Radeons -- which have no performance penalty for using more registers.  You could use every single register the Radeon has and there would be no performance hit.  As such, the increased instruction count is purely detrimental to performance.Someone at the Beyond3D.com forums demonstrated this comparing the a shader''s performance in Cg to Direct3D''s HLSL.  The result was that the HLSL version performed 20% better.  That new Tomb Raider game also apparently has a way to force Cg to be used.  On a Radeon, the HLSL version performs better.The languages themselves certainly don''t hold any advantages over each other -- at least on a Radeon.  Cg may be better for GeforceFXs than GLSL because Cg explicitly supports specific precision (and GeforceFXs receive less of a performance hit for using more FP16 registers), but the same is not true for Cg versus D3D''s HLSL.  HLSL does explicitly support multiple precisions (well, two), so for DirectX programmers Cg isn''t really anything special. 