[Bf-viewport] OpenGL low level shader API proposal

[Jacob Merrill]

would this new viewport also modify the material system?

PBR an NPR workflow?

and obligatory - Will this render bge usable by the bge? will it
boost performance their also?


On Sat, Dec 5, 2015 at 3:34 PM, Mike Erwin <significant.bit at gmail.com>
wrote:

> Yes, thank you! Interesting stuff. Here's my first round of notes:
>
> +1 for immutable draw state.
> +100 for minimizing state changes! Marry desired state to the draw call.
>
> Re: Uniform Buffer Objects -- Compatibility with GL 2.1 is a temporary
> concern, so anything we do there should be minimal and marked for future
> removal.
>
> For passing in the current transformation, I don't think the lowest-level
> API should treat this or any other inputs special. Do like the convenience
> of not having to specify CTM every time though... maybe I'm on the fence
> about this one! Since a lot of this has to do with UI drawing, how about a
> dedicated 2D transformation system, stack or otherwise? See bottom part of:
> http://wiki.blender.org/index.php/Dev:2.8/Source/OpenGL/Transformations
> 3D shaders would automatically get a 3x4 ModelView and 4x4 Projection
> matrix, maybe a 4x4 MVP for efficiency. 2D shaders would automatically get
> a 2x3 ModelView matrix and that's it.
>
>
> Some basic assumptions, definitions, questions... please let me know if
> any of these are way off:
>
> GPUShader is a compiled & linked set of Vertex shader, optional Geometry
> shader, and Fragment shader.
>
> Inputs for the GPUShader are the active uniforms (which could be from any
> of the above shader stages) and vertex attributes from the first stage.
>
> Uniform values are set once per draw. Attribute values are typically set
> per vertex from data in VBOs. Attributes can also be set once per draw
> using glVertexAttrib, acting more like uniforms from client program's point
> of view.
>
> Uniforms can have default values in GLSL. Is there any way to query the
> program to see if an input *requires* us to set a value? Beyond parsing the
> GLSL source text.
>
> Anyone interested in parsing GLSL source text?
>
>
> Mike Erwin
> musician, naturalist, pixel pusher, hacker extraordinaire
>
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>
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