Rendering issues when rendering OSM buildings with ModelExperimental

[ptrgags]

In This forum thread, a Sandcastle was presented to demonstrate incorrect rendering.

I think I see 3 problems here:

1. OSM buildings use the CESIUM_primitive_outline glTF extension, this is not yet implemented. This was mentioned in 3D Tiles Next CesiumJS Roadmap #9520
2. It seems like the lighting is using a constant normal (which could be the default normal in the model material?
   
3. The dropdown option "Color by Distance to Selected Location" breaks the shader. Might have to do with fetching metadata. Note that OSM buildings uses the batch table hierarchy extension, not sure if that has an impact here.
   

[j9liu]

Making a note: when we add support for CESIUM_primitive_outline can we test if the bug in #10452 comes up?

[ptrgags]

Today I discovered that the problem isn't a constant normal (Cesium OSM buildings do have normals!) but that the material is rendering as too shiny, that's just the IBL reflecting the sky. It is more noticeable compared to the old Model, not sure why.

And I'm currently working on CESIUM_primitive_outline support in ModelExperimental. (not quite ready for a PR yet, but I can at least render outlines locally!). The lighting looks a bit off, but it's a lot better than before!
.

[kring]

Yeah Cesium for Unreal renders the buildings as crazy shiny, too. I think the problem is that I chose the material parameters in Cesium OSM Buildings based on the old Model code, and that didn't fully capture the shine I was putting on it.

[ptrgags]

Now that #10506 is merged, I'm closing this too. Here's a screenshot from the current main: