Hi,
I'm going to implement GLSL 1.0 support for r300 and I have few questions.
The problem is r300 and r400 hw doesn't support branching/loops. For loops
there's no other way than fallback to software, but I can do branching by
executing all branches and then selecting result depending on condition.
Let's take a look at this shader (in pseudo-code):
if (some_vec4 > {2.0, 3.0, 1.0, 0.0})
some_code;
else
other_code;
endif
It would be translated into something like this:
SGT TEMP[1].w, TEMP[0].xyzw, CONST[0].xyzw
IF TEMP[1].wwww
some_code;
ELSE
other_code;
ENDIF
How should I understand that IF instruction? If all components are greater
than zero, or only one have to be greater than zero, or maybe all components
must equal to 1.0?
What if the condition be something like this (var.xw > {2.0, 0.0})?
Is it even legal to compare only selected vector components?
If so, how would the code look like after translation?
Regards,
Maciej Cencora
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