Explain how to use occlusion strength from glTF in PBR

[UX3D-haertl]

occlusion strength is used in glTF with the following formula: 1.0f + occlusionStrength * (sampledValue - 1.0f) Ref: https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#_material_occlusiontextureinfo_strength.

This can be restructed to occlusionStrength * sampledValue + (1.0f-occlusionStrength), which can be supplied to outTransform and outOffset. This should be added as a note.