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gallium: add caps for POSITION and FACE system values

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v2: document the integer behavior

Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com
Reviewed-by: Brian Paul <brianp@vmware.com>
This commit is contained in:
Marek Olšák
2016-01-02 20:45:00 +01:00
parent 24737f2298
commit 34738a92de
17 changed files with 48 additions and 6 deletions
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5
src/gallium/docs/source/screen.rst
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@@ -292,6 +292,11 @@ The integer capabilities:
supported in vertex shaders.
* ``PIPE_CAP_TGSI_PACK_HALF_FLOAT``: Whether the ``UP2H`` and ``PK2H``
TGSI opcodes are supported.
* ``PIPE_CAP_TGSI_FS_POSITION_IS_SYSVAL``: If state trackers should use
a system value for the POSITION fragment shader input.
* ``PIPE_CAP_TGSI_FS_FACE_IS_INTEGER_SYSVAL``: If state trackers should use
a system value for the FACE fragment shader input.
Also, the FACE system value is integer, not float.
.. _pipe_capf:

19
src/gallium/docs/source/tgsi.rst
View File

@@ -2658,7 +2658,8 @@ space coordinate system. After clipping, the X, Y and Z components of the
vertex will be divided by the W value to get normalized device coordinates.
For fragment shaders, TGSI_SEMANTIC_POSITION is used to indicate that
fragment shader input contains the fragment's window position. The X
fragment shader input (or system value, depending on which one is
supported by the driver) contains the fragment's window position. The X
component starts at zero and always increases from left to right.
The Y component starts at zero and always increases but Y=0 may either
indicate the top of the window or the bottom depending on the fragment
@@ -2770,11 +2771,17 @@ typically only used for legacy graphics APIs.
TGSI_SEMANTIC_FACE
""""""""""""""""""
This label applies to fragment shader inputs only and indicates that
the register contains front/back-face information of the form (F, 0,
0, 1). The first component will be positive when the fragment belongs
to a front-facing polygon, and negative when the fragment belongs to a
back-facing polygon.
This label applies to fragment shader inputs (or system values,
depending on which one is supported by the driver) and indicates that
the register contains front/back-face information.
If it is an input, it will be a floating-point vector in the form (F, 0, 0, 1),
where F will be positive when the fragment belongs to a front-facing polygon,
and negative when the fragment belongs to a back-facing polygon.
If it is a system value, it will be an integer vector in the form (F, 0, 0, 1),
where F is 0xffffffff when the fragment belongs to a front-facing polygon and
0 when the fragment belongs to a back-facing polygon.
TGSI_SEMANTIC_EDGEFLAG