When trying to read from a 3D texture with a R32F or R32UI formats via an image binding in a compute shader, the value returned is always 0 (using imageLoad function). If I read from the same texture using a sampler instead (using texelFetch) the value returned as expected. Reading from a texture with RGBA8 format via image binding is also successful.
I have confirmed the above behaviour in an isolated case and have a GLSL shader to reproduce it, but the website doesn’t allow me to upload an attachment.
I do not get any OpenGL errors reported during the texture data upload or the compute dispatch.
Writing via an image binding might also not work, but I have not yet confirmed that in an isolated scenario.
EDIT: just wanted to mention that the same code runs fine on other mobile GPUs.
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Would it be possible to provide a Development build of an Android application reproducing the issue? You can use our Support email IMG-InternalSupportDevTechEcosystem@imgtec.com in case that makes handling the application easier.
I’ve sent an email with the application to the email address you provided.
For anyone else reading this: I’ve pinpointed the core of the issue - imageLoad fails unless the texture has its min/mag filters set to GL_NEAREST, even though the sampler state and/or mipmap-completness probably shouldn’t matter for the purpose of imageLoad/Store operations (and other drivers seem to happily ignore it).
It seems the code must follow the spec, where integer textures do not support linear filtering. GL_TEXTURE_MAG_FILTER must be GL_NEAREST and GL_TEXTURE_MIN_FILTER either GL_NEAREST or GL_NEAREST_MIPMAP_NEAREST ( Texture - OpenGL Wiki ). This makes the code work correctly.
