x3d-serializer improvements

[andreasplesch]

Expected Behavior

• [x] Output should use diffuseColor for polygons, emissiveColor for line geometry.
• [x] Output should show creases, optionally smoothed.
• [x] Output should be aligned such that +Y becomes the Up vertical direction.
• [ ] Output should condense uniform vertex colors to Material
• [ ] Output should add a bit of specular highlight as in default renderer

Actual Behavior

Output uses diffuseColor + emissiveColor. Output uses averaged normals for smoothing (the X3D default). Output is rotated such that +Y is horizontal. Output has long list of vertex colors even when uniform. Output is a bit dull.

Steps to Reproduce the Problem

1. serialize basicColors example to X3D
2. load X3D into X3D browser such as x-ite or x3dom
3. observe colors, smoothing, and orientation

Specifications

• Version: main branch
• Platform: web
• Environment: browser

See more complete discussion at #1234.

These are relatively simple changes to the X3D serializer. I can generate a unified PR, or separate PRs for each suggestion. Please advise.

[hrgdavor]

@andreasplesch I see you are pretty active lately. If you feel like it you can also join jscad discord channel https://discord.gg/AaqGskur93 where we talk more than issues.

[andreasplesch]

Thanks ! I joined the channel. I am also using the discussions tab here on github to keep things in one place.