[Mesa-dev] TGSI and Tessellation Control Shader outputs

[Marek Olšák]

On Tue, Sep 16, 2014 at 5:42 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> OK, so just to summarize:
>
> The approach suggested by Roland is to have the outputs be
> one-dimensional and only representing the current invocation's
> per-vertex outputs. Each invocation would also get access to other
> invocations' per-vertex outputs via a 2d input array.
>
> So a shader might look something like
>
> TESSC
> DECL IN[][0], POSITION (input patch's per-vertex position)
> DECL IN[][1], GENERIC (input patch's per-vertex generic attribute)
> DECL IN[][2], TCS_POSITION (output patch's per-vertex position)
> DECL IN[][3], TCS_OUTPUT (output patch's per-vertex generic attribute)
> DECL OUT[0], POSITION
> DECL OUT[1], GENERIC
> DECL OUT[2], PATCH
>
> And then anything written to OUT[0] would be aliased via IN[][2].
> Roland, does that sound right? This seems kinda nasty that there are
> going to be 2 types of position/pointsize/clipdistance inputs -- do
> you have a better suggestion for handling that?

The output-as-input arrays can be declared as system values (SV), then
you don't need to duplicate semantic names.

Marek