Marek Olšák wrote:
On Thu, Jun 24, 2010 at 12:25 AM, Marek Olšák <mar...@gmail.com
<mailto:mar...@gmail.com>> wrote:
On Wed, Jun 23, 2010 at 11:51 PM, Corbin Simpson
<mostawesomed...@gmail.com <mailto:mostawesomed...@gmail.com>> wrote:
Yep, it's that time again. These are just things marked in the
docs as
unknown, so I'm not grinding any axes, just cleaning stuff up.
~ "If a surface includes several layers/slices (XXX: not yet...)
then
all layers will be cleared." From the information on
pipe_context::clear(). Is this just wishful thinking, or do drivers
need to implement this?
I believe this has something to do with geometry shaders where you
can select a layer (slice, face) you want to emit a primitive to.
This way you may e.g. render to a whole cubemap in one pass.
~ An explanation of dual-source blends and how they work would
be nice.
http://www.opengl.org/registry/specs/ARB/blend_func_extended.txt
~ If logicop_enable and independent_blend_enable are set, are lops
performed for all render targets, or only those that have
blend_enable
set?
~ PIPE_CAP_TEXTURE_SHADOW_MAP and PIPE_CAP_MAX_PREDICATE_REGISTERS
aren't explained.
I think PIPE_CAP_TEXTURE_SHADOW_MAP means shadow samplers.
~ PIPE_CAP_GUARD_BAND_* obviously refers to the guard bands, but
what
exactly do they mean as capabilities? Maximum guard band settings?
Minimum?
~ Could somebody explain exactly what's up with the RCC opcode? Its
definition is kind of ridiculous: dst = (1 / src.x) > 0 ? clamp(1 /
src.x, 5.42101e-020, 1.884467e+019) : clamp(1 / src.x,
-1.884467e+019,
-5.42101e-020)
~ Are we going to introduce new cap bits for parts of the TGSI ISA?
(I'll understand if this is off the table for now.)
~ TGSI_SEMANTIC_POSITION is (x, y, z, w) where x, y, and z are
position, and w is the homogeneous coordinate. Is w also for
perspective divide? Is the perspective divide configurable, or is it
always done in shaders?
The perspective divide is done per-pixel after the rasterization and
before the fragment shader, and there is no way to disable it in
Gallium. It's never done in shaders, it's rather a fixed
functionality and imposing additional restrictions on it would make
it hard to implement in drivers.
Hm, it's done during the rasterization, actually.
Divide by W takes place in two places:
1. Per-vertex to convert clip coords into normalized device coords.
2. During fragment shader attribute interpolation to do
perspective-corrected interpolation. Actually, we usually have 1/W at
this point so it's a multiplication.
I've rewritten the Gallium docs for TGSI_SEMANTIC_POSITION/COLOR/BCOLOR.
-Brian
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