Shader performance on rPi

Hello again, everyone! So I’ve been working on a project on the Raspberry Pi which basically uses GLES shaders drawing fullscreen, i.e., fragment shaders doing all the drawing - and the performance seems to be quite terrible on even simple random/perlin noise based shaders (I’m talking 5 fps or less). I’m wondering if there’s some tweaking that needs to be done somewhere, something obvious I’m missing or is the Pi just that weak when it comes to running shaders?

The GPU has been allocated 512mb of memory already, so I don’t think that would be an issue…

I’ve tried on both Stretch and now Jessie with 0.9.8 Nightly, GL legacy driver selected on the Pi.

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So it looks like there are massive slowdowns if I’m calling functions declared outside main() in the frag file but if I do everything within main, it’s reaching acceptable behaviour. Interesting!