OpenGL 4.0

MilfredCubicleX · 2010-03-15T14:38:13

It looks like the spec for OpenGL 4.0 has come out: http://www.opengl.org/registry/ Reading through it, it looks like the most notable change is the addition of "Tessellation Control Processor" and "Tessellation Evaluation Processor". From the GLSL spec: Quote:The tessellation control processor is a programmable unit that operates on a patch of incoming vertices and their associated data, emitting a new output patch. Compilation units written in the OpenGL Shading Language to run on this processor are called tessellation control shaders. When a complete set of tessellation control shaders are compiled and linked, they result in a tessellation control shader executable that runs on the tessellation control processor. The tessellation control shader is invoked for each vertex of the output patch. Each invocation can read the attributes of any vertex in the input or output patches, but can only write per-vertex attributes for the corresponding output patch vertex. The shader invocations collectively produce a set of per-patch attributes for the output patch. After all tessellation control shader invocations have completed, the output vertices and per-patch attributes are assembled to form a patch to be used by subsequent pipeline stages. Tessellation control shader invocation run mostly independently, with undefined relative execution order. However, the built-in function barrier() can be used to control execution order by synchronizing invocations, effectively dividing tessellation control shader execution into a set of phases. Tessellation control shaders will get undefined results if one invocation reads a per-vertex or per-patch attribute written by another invocation at any point during the same phase, or if two invocations attempt to write different values to the same per-patch output in a single phase. The tessellation evaluation processor is a programmable unit that evaluates the position and other attributes of a vertex generated by the tessellation primitive generator, using a patch of incoming vertices and their associated data. Compilation units written in the OpenGL Shading Language to run on this processor are called tessellation evaluation shaders. When a complete set of tessellation evaluation shaders are compiled and linked, they result in a tessellation evaluation shader executable that runs on the tessellation evaluation processor. Each invocation of the tessellation evaluation executable computes the position and attributes of a single vertex generated by the tessellation primitive generator. The executable can read the attributes of any vertex in the input patch, plus the tessellation coordinate, which is the relative location of the vertex in the primitive being tessellated. The executable writes the position and other attributes of the vertex. I'm not sure that I see how this would be very useful. Any thoughts?

Graphics and GPU Programming Programming OpenGL

Started by MilfredCubicleX March 11, 2010 09:50 AM

9 comments, last by Enalis 14 years, 1 month ago

Enalis

333

March 15, 2010 02:38 PM

Hah, all the posts make so much sense now, thank you! I kinda feel dumb as I've been tinkering with OpenGL for far too long to not know this. Especially since I've used this plenty of times. I guess GLEW always hid the extension loading from me.

Douglas Eugene Reisinger II
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OpenGL 4.0

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OpenGL 4.0

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