glBindAttribLocation does not take effect until the program is
re-linked. In other words I was doing it wrong!
New code gets attrib locations from program, then remembers the attrib
-> location mapping for subsequent draw calls.
The program and VertexFormat are not modified (makes threading and reuse
easier).
There are older ways to give OpenGL hints about buffer invalidation, but
glInvalidateBufferData does exactly what we want. Use this function when
OpenGL 4.3 is available (Windows and proprietary Linux drivers).
Part of Gawain immediate mode.
glMapBufferRange is a wonderful function that doesn’t exist on GL < 3.0.
Use the APPLE_flush_buffer_range extension on Mac. It offers several of
glMapBufferRange’s benefits.
Use older “black arts” method to orphan VBOs when we are done with
them. In modern OpenGL this behavior is more obvious.
Add APPLE_flush_buffer_range to Mac requirements. Every GPU is
supported. T49012
Apple invented VAOs and exposes them via an extension in legacy GL.
Other platforms use at least GL 3.0 which has VAOs built in.
QUADS were removed from core profile but are useful for immediate-mode
drawing. We’ll have to implement our own QUAD drawing before switching
to core profile.
Immediate mode no longer leaves its internals bound after use. Part of
transition from a simple prototype app to non-simple Blender, which has
lots of other parts using OpenGL.
More ways to send values via immAttrib:
2D float vectors
3 & 4 component ubytes (for colors mostly)
New immVertex functions that act more like familiar glVertex. We’ll
find a balance between making this API convenient and keeping it small.
2f and 3f are enough for now.
Introducing an immediate mode drawing API that works with modern GL 3.2
core profile. I wrote and tested this using a core context on Mac.
This is part of the Gawain library which is Apache 2 licensed. Be very
careful not to pull other Blender code into these files.
Modifications for the Blender integration:
- prefix filenames to match rest of Blender’s GPU libs
- include GPU_glew.h instead of <OpenGL/gl3.h>
- disable thread-local vars until we figure out how best to do this
