Potential divide by zero in Bloom shader

[oncer]

If you look inside Assets/Kino/Bloom/Shader/Bloom.cginc in the prefilter part:

    // Under-threshold part: quadratic curve
    half rq = clamp(br - _Curve.x, 0, _Curve.y);
    rq = _Curve.z * rq * rq;

    // Combine and apply the brightness response curve.
    m *= max(rq, br - _Threshold) / max(br, 1e-5);

Half is a 16-bit floating number on some platforms (see Unity docs). The smallest "normal" number for a 16-bit float is 0.000061035, so 1e-5, or 0.00001 is either denormalized or flushed to zero, depending on the shader compiler, potentially resulting in nan values for fragments with calculated brightness of 0.
I can confirm this happens on Nintendo Switch, probably some mobile platforms too. The areas with nan values in the prefilter texture will get passed down in the downsample/upsample passes and result in black rectangles in the final renderbuffer.
Changing this value from 1e-5 to 6.2e-5 resolves the issue.

[keijiro]

Thanks for pointing it out. I think this has been fixed in the post-processing stack. I'm not using this effect (KinoBloom) any more, but I'll fix it if there is any chance to update this for some reason.

[larssteenhoff]

Thanks for the fix, I'm still using it