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"Cubemap Size" affects procedural texture's scale in the reflections
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Win 10, GTX 1080
Blender 2.80 2019-02-19 23:18 855b3e68ef27

When you bake a cubemap at lower resolutions like 128px, procedural textures have incorrect scale in reflections:

See attached blend file:



Event Timeline

What you see is a combination of a moire effect, due to small scale of the texture and the low cubemap resolution. Another way of putting it, the texture is so small than when it's captured on the cubemap filtered at a lower res, it just happens to look like a large scale version of the same texture, an optical illusion. But if you use any other procedural texture, or the texture at a larger size, you see that lowres cubemaps don't change their scale. Like in this image with the lowest cubemap resolution possible.

Moire effect doesn't explain this:

It's a simple noise texture with a scale of 100.

If it's indeed a moire effect then i guess it needs better filtering.

The noise is smaller than the size of a pixel in the cubemap, and thus the small noise disappears in the downscale process while the few ones that appear look big because that's how big the pixels are. It's like downsampling a picture of stars in photoshop, that's what happens, and no filtering algorithm would solve that 100%. It's definitely NOT procedural textures changing scale, because then it would change scale even with big textures like in the imaged I used above

Ok then, If there's nothing to be done about it.