My project should greatly benefit from arbitrary/atomic read and write operations in a texture from glsl shaders. The Image load store extension is what I need. Only problem, my target platform does not support OpenGL 4. Is there an extension for OGL 3 that achieves similar results? I mean, atomic read/write operations in a texture or shared buffer of some sort from fragment shaders.
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1 Answers
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Image Load Store and, especially atomic operations are features that must be backed up by specific hardware capabilities, that are very similar to features used in compute shaders. Only some of the GL3 hardware can handle it and only in a limited way.
Image Load Store in core profile since 4.2, so if your hardware (and driver) is capable of OpenGL 4.2, then you don't need any extensions at all
if your hardware (and driver) capabilities is lower than GL 4.2, but higher than GL 3.0, you can, probably, use
ARB_shader_image_load_storeextension.- quote:
OpenGL 3.0 and GLSL 1.30 are required - obviously, not all 3.0 hardware (and drivers) will support this extension, so you must check for its support before use it
- I believe, most NVIDIA GL 3.3 hardware supports it, but not AMD or Intel (that's my subjective observations ;) ).
- quote:
If your hardware is lower than GL 4.2 and not capable of this extension, nothing really you can do. Just have an alternative code path with texture sampling and rendering to texture and no atomics (as I understood this is possible, but without "great benefit of atomic"), or simply report an error to those users, who not yet upgraded their rigs.
Hope it helps.
