----- Original Message -----
> On 12/13/2011 09:11 PM, Jose Fonseca wrote:
> >
> >
> > ----- Original Message -----
> >> This is an updated version of the patch set I sent to the list a
> >> few
> >> hours
> >> ago.
> >
> >
> >> There is now a TGSI property called
> >> TGSI_PROPERTY_NUM_CLIP_DISTANCES
> >> that drivers can use to determine how many of the 8 available clip
> >> distances
> >> are actually used by a shader.
> >
> > Can't the info in TGSI_PROPERTY_NUM_CLIP_DISTANCES be easily
> > derived from the shader, and queried through
> > src/gallium/auxiliary/tgsi/tgsi_scan.h ?
> >
> >
> > Could you also elaborate on why TGSI_SEMANTIC_CLIPDIST is useful
> > for the drivers? I personally don't have nothing against it, but
> > just like to understand why it makes a difference.
> >
>
> Why does TGSI_SEMANTIC_*POSITION* make a difference ?
>
> Right, because the position values are consumed by the fixed function
> rasterizer. So are the clip distances.
>
> This is not about pipe_clip_state.ucp but about what this legacy
> cruft
> has to be turned into if GL_CLIP_PLANEi is used instead of GLSL 1.3's
> gl_ClipDistance[i].
I'm just surprised because I thought there was no more fixed function clipping.
Can you give an example of such legacy cruft?
> The same mentality ("What's information useful for ?") cost me
> TGSI_SEMANTIC_TEXCOORD and now I have to rely on a hack to make point
> coordinate replacement work on nvc0
> (http://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/drivers/nvc0/nvc0_program.c#n29).
>
> I'm sorry I'm a bit sensitive on the issue of dropping information at
> the gallium threshold.
Please don't vent it on me. As I explicitly said, I don't oppose (I imagined
there was a good reason), and I'm asking for my own education.
And these are questions that always need to be asked. Or even better, should
be answered from the start -- commit messages in general, and interface changes
in particular, should not just summarize what its being changed, but also _why_
it changed. The patch series included no pipe driver changes, so it's not
possible even to induce from them.
Concerning TGSI_SEMANTIC_TEXCOORD I can't remember/comment if/what/why it was
decided like that. Please start a new thread and a link to any previous thread
if you wanna revisit it.
I'm sorry the choices done in gallium cause you so much grief. But dropping
information is a trade off between simple interface and a rich interface, and
not inherently bad or good. The only question is have the right trade offs been
made. And there's always room for improvement.
Jose
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