Various Khronos samples broken by quantization

[donmccurdy]

Examples:

• BoxTextured
• BrainStem
• CesiumMan
• MorphStressTest
• DragonAttenuation
• RiggedFigure
• RiggedSimple
• TextureSettingsTest
• TextureTransformMultiTest

[donmccurdy]

Volume attenuation distance is a distinct problem, already reported at mrdoob/three.js#22343.

The rest — particularly texture settings, skinning, and morph targets — are likely to represent bugs in the quantize() function implemented here.

[donmccurdy]

Many issues fixed in #333.

A few remaining:

• Broken morph targets (screenshots above)
• Skinned mesh offsets (upstream bug)
  • Bounding box for quantized models computed incorrectly? google/model-viewer#2450
  • SkinnedMesh: Incorrect bounding box and culling mrdoob/three.js#14499
• Need to update volume extension
  • MeshPhysicalMaterial: Volume attenuation in world or local units? mrdoob/three.js#22343

[donmccurdy]

Not a bug, but quantization currently skips any texture coordinates extending beyond the [0,1] range. Could improve completeness by quantizing, adding KHR_texture_transform when those are encountered.

[donmccurdy]

Closing this and filing the remaining tasks as new issues:

• quantize: include UVs outside [0,1] range #335
• quantize: update 'KHR_materials_volume' thickness #336