ensure bump map scale is texture UV scale invariant. adjust examples.

[bhouston]

Description

Right now our bump scale is dependent upon the texture UV scale in world space. This is incorrect, rather a bump map should look the same regardless of the texture UV scale in world space. Our normal factors are invariant to texture UV scale, it is just the bump scale that isn't.

By fixing this, this allows us to use more sensible scale factors that are close to 1.0 by default. Otherwise we had to use weird 0.01 scale factors or similar if the texture UV scale in world space wasn't close to unity.

You can see here how we made the normal factors texture UV scale invariant, it is the normalization right here using the determinant scale:

https://github.com/mrdoob/three.js/blob/dev/src/renderers/shaders/ShaderChunk/normalmap_pars_fragment.glsl.js#L36C2-L36C2

Also in Babylon.js, they are normalizing the texture UV space in this code, which they label "construct a scale-invariant frame":

https://github.com/BabylonJS/Babylon.js/blob/master/packages/dev/core/src/Shaders/ShadersInclude/bumpFragmentMainFunctions.fx#L105

This is a breaking change to anyone who is using bump map scale factors. But I believe it should increase our compatibility with other systems who do this correctly.

This contribution is funded by Threekit

[bhouston]

We made this change to Exocortex/Threekit's internal Three.js 7 years ago and forgot to contribute it back to the community.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

Filesize dev	Filesize PR	Diff
649.1 kB (160.9 kB)	649.2 kB (160.9 kB)	+26 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

Filesize dev	Filesize PR	Diff
442.4 kB (107 kB)	442.4 kB (107.1 kB)	+26 B

[Acyapinsa]

Sorry something is not right with this now. The bump has some relation to the camera distance?
near

far

[Shane-oo]

Is it possible to know the factor on which we should increase our bump scales by?
Is it using the textures scale? I am not able to simply go and increase bump scale as they are configurable and have over 1000.
So I'm looking for a mathematical formula I can use to increase all bump map scales deterministically.
Thanks!

[mrdoob]

@bhouston ping?

[LR17]

It seems that the bump is more visible when the camera is far from the object. I have this impression too.