Somewhat more conventional visual presentation:
+ Use a neutral gray background a-la most other CAD/modelling software
for better contrast with the geometry (which defaults to a bright
yellow). This is done with the "skybox-environment" image in
model-viewer, so add a new setting value in settings.ts for this (it
can be overriden in the URL just like other settings)
+ But using a skybox will cause that image to be used for lighting
too, which is clearly not desired. So fetch a nice professional
HDRI image from Polyhaven for lighting. This is much better (more
directional, higher contrast) than the default light environment
anyway.
+ The checkerboard texture isn't really a good default. Use a 1x1
white pixel instead, essentially presenting the model materials
unchanged.
Also collect the default color in gltf.py out of the code and put it
next to the texture for clarity. This should probably be wired
through to a setting at some point.
Signed-off-by: Andy Ross <andy@plausible.org>
