Hello,
As discussed with a few people on XDC I am mailing my current version of the
WINEX_provoking_vertex extension to this list. For more details and what this
is about refer to the description of the extension.
Best regards,
Stefan
XXX - not complete yet
Name string: WINEX_provoking_vertex
GL name: GL_WINEX_provoking vertex
Contributors:
Stefan Dösinger <[EMAIL PROTECTED]>
Summary:
This extension allows GL clients to specify which vertex of a triangle
determines the color of a primite. This is needed by Wine, a software that
implements the Microsoft Windows API, including Direct3D, on top of Unix, X11
and OpenGL. In Direct3D, the first vertex decides the color, while in OpenGL
the last does that.
New functions and procedures:
ProvokingVertexWINEX(enum vertex);
New tokens:
Accepted by ProvokingVertexWINEX:
FIRST_VERTEX_WINEX 0x????
LAST_VERTEX_WINEX 0x????
Accepted by Get*
PROVOKING_VERTEX_WINEX 0x????
Issues:
1.a) Which name should the extension have? The name provoking_vertex was
inspired by the register documented in the ATI r500 GPU documentation which
configures this feature on the hardware side
1.b) Should we use MESA instead of WINE? There are a few MESA extensions
already, but no WINE extensions(other than Wine-internal ones). Still more of
those may appear in the future
2) Which options should this extension offer? The r500 documentation mentiones
first, second, third and last vertex as possible provoking vertices. OpenGL
default is LAST_VERTEX_WINEX, Wine needs FIRST_VERTEX_WINEX for Direct3D.
Providing too many options may make this extension unimplementable on other
implementations, but the other options may be useful for other purposes
Resolved: Just stick to FIRST_VERTEX_WINEX and LAST_VERTEX_WINEX for now.
Secound vertex and third vertex cause issues with points and lines.
3) Trademarks, political correctness? OpenGL extensions never talk about
Direct3D, only "another popular 3D API"(see NV_texture_shader and
ARB_fragment_program)
4) Specifying the extension formally. Which chapters to modify? Where to get
enumeration values from?
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