On 27.05.2015 18:28, Marek Olšák wrote:
Another thing to consider is linking shaders that occur before the
rasterizer (e.g. any two shaders from VS->TCS->TES->GS). The maximum
number of written distances is still 8, but what happens if VS writes
1x clip and 7x cull and GS reads 8x clip and no cull?
i think this should be rejected anyway (in the glsl?!), constraining vs
output to be the same as gs input where the last definition is the valid
one....
In this case
it's basically a generic varying. How is linking separate shaders
supposed to work with one combined clip-or-cull array? It doesn't seem
to be possible.
Marek
On Mon, May 25, 2015 at 5:07 PM, Ilia Mirkin <[email protected]> wrote:
On Mon, May 25, 2015 at 9:40 AM, Tobias Klausmann
<[email protected]> wrote:
On 25.05.2015 07:17, Dave Airlie wrote:
On 25 May 2015 at 08:11, Marek Olšák <[email protected]> wrote:
It's the same on Radeon. There are 2x ClipOrCullDistance output
vectors and a mask saying it should clip or cull or do nothing.
Marek
My thinking was gallium should have a single semantic and a mask in
the shader definition maybe.
though it doesn't solve the does nvidia do the right thing with
cull[0] and clip[0], and what is the right thing.
Dave.
I'm still convinced that both clip[0] and cull[0] should be possible. Plus i
have written a shader_test for this a while ago which you pushed to piglit
(fs-cull-and-clip-distance-different.shader_test). If i remember right
nvidia passed that test just fine.
Ah btw, if we follow Brian Paul, overlapping indexes are fine! (and it
is way more intuitive to use for a shader developer)
My take (and note that I last read the extension many months ago) is
that you're supposed to figure out the max gl_ClipDistance[] written,
and then write all your cull distances above that. So if you, e.g.,
have something like
gl_ClipDistance[5] = 1;
gl_CullDistance[0] = 1;
Then it would decide that there are 6 clip distances (or if there's an
explicit out float gl_ClipDistance[n], then use that), and 1 cull
distance. In the TGSI, I'm thinking this might look approximately like
PROPERTY CULL_MASK (1<<6)
DCL OUT[0], CLIPDIST[0]
DCL OUT[1], CLIPDIST[1]
MOV OUT[1].y, 1 (clip distance[5])
MOV OUT[1].z, 1 (cull distance[0])
Then basically you'd have
(rast->clip_enable & shader->actual_clip_writes_mask) | cull_mask =
the enabled distances
cull_mask = cull mask
This would work *very* well for nouveau, not sure how suitable it is
for other hardware.
Cheers,
-ilia
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