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The following issue is also logged here, which links to the relevant files
Platform details are at the end.
This fragment shader:
https://github.com/mc-imperial/shader-compiler-bugs/raw/master/ARM-Mali-T628-Chromebook-WebGL/wrong_images/small-v100-we…
causes this image to be rendered:
In contrast, this shader:
https://raw.githubusercontent.com/mc-imperial/shader-compiler-bugs/master/ARM-Mali-T628-Chromebook-WebGL/wrong_images/sm…
causes the following similar but visually distinct image to be rendered:
The shaders are identical, except in the second shader, this line from the first shader:
vec3 b = fract(sin(co.x * 0.3e-3 + co.y) * vec3(8.1e5, 1.0e5, 0.1e5));
has been replaced by:
vec3 b = fract(sin(co.x * 0.3e-3 + co.y) * (vec3(8.1e5, 1.0e5, 0.1e5) + vec3(injectionSwitch.x, 0.0, 0.0)));
At runtime, we set injectionSwitch to (0.0, 1.0), so adding vec3(injectionSwitch.x, 0.0, 0.0) should be like adding a vector of zeroes; i.e., it should have no effect. Yet making this change causes a visible difference in the image that is rendered.
vec3(injectionSwitch.x, 0.0, 0.0)
Platform details:
- Samsung Chromebook
- Chrome OS
* Version: 54.0.2840.101
* Platform: 8743.85.0 (Official Build) stable-channel peach_pit
* Firmware: Google_Peach_Pit.4482.95.0
- GPU: ARM Mali-T628
Version and renderer info obtained via WebGL API:
Hi Ally,
We've not managed to reproduce this with the latest driver for the Midgard GPU family (Mali-T* GPUs), so it's possibly already fixed in devices running a newer release drivers.
We're trying to work out exactly when this was fixed to give you a more precise driver revision to aim for, and will provide feedback to the device manufacturer.
Kind regards, Pete