koobas.hobune.stream
Batch texture sampling in shader?
Is there a batch texture sample function I can use to test an array of uv coords or something similar, which won't slam performance? Currently calling tex2D quite a few times within my shader, and just wondering if there's a way to call an optimized version of it.
Want to sample a texel and the 8 texels surrounding it, for each texel.
Alternatively, can we predict the order in which texels will be sampled and/or store the results of the sample for use in the next frag call? I could cut down the number of calls necessary if I can 'remember' some of the previously sampled texels.
By the nature of the graphics pipeline, it's impossible for a frag shader to "remember" values from previous fragments or pass them to other programs - shaders are stateless and independent, processed in parallel.
That's why blur effects are relatively expensive - because they use a kernel similar to that you describe in which each pixel must sample its neighbours - creating multiple texture reads for each fragment (which then will inevitably be sampled again for another pixel)
A pity. Thanks for the response though.
So it's safe to say that any optimizations (or insight into how to achieve them) I could hope to achieve will likely be present in current blur shaders?
I haven't exa$$anonymous$$ed it closely, but I think it's reasonable to assume that the Blur image effect that comes with Unity 5.x is relatively well-optimised and represents the current industry standard in creating such effects (certainly, it's been written and tested by pretty smart people who know more about the Unity rendering pipeline that most of us here....).
Of course, that's designed as a generic, all-purpose blur effect - it might be possible to write a more efficient blur shader that is specific to the needs of your project, but you'll need pretty good shader knowledge to achieve that I'd say.
