Add support for 3D Tiles Styling Language about cesium-unreal

[j9liu]

Hi @yuziqii,

The project board you linked hasn't been updated in a long time 😅 Yes, we have updated Cesium for Unreal to support EXT_mesh_features and EXT_structural_metadata as of version 2.0.0. But it looks like you're talking about styling with the 3D Tiles styling language in CesiumJS. Yes, this is fairly different from the current system.

Those limitations that you listed are true, and they're due to several factors:

• The code to programmatically generate a material only works in the Editor, and won't work in an actual game.
• As far as I know, it's not possible to modify nodes of a material at runtime. It would force recompilation of the shaders.

So unfortunately, to take advantage of Unreal's node-based material graphs, you have to do it all at the beginning, and it can't be changed at runtime.

However, your work with the 3D Tiles styling language looks awesome! This would be a cool community contribution, if you're willing.

Regarding your question, I don't think I follow. The Mask blend mode is not meant to be used for translucency. It defines an alpha "cutoff" value. Anything below this value will be completely transparent, and anything above it will be completely opaque. You won't be able to use it for translucency. Is there something that makes the other blend modes not sufficient for your use case?

[yuziqii]

@j9liu Thanks for your reply.

The reason I use the Translucent blend mode is to ensure that the styling result matches that of CesiumJS. In CesiumJS, the styling result can be translucent. If I use the Mask blend mode, it will not be able to achieve translucency, which I believe is not an ideal solution. In this scenario, I can utilize the 'Lerp' function to blend the original color and styling color with opacity. However, this approach will not result in translucency, it will simply blend the layer base color.

Therefore, I prefer the 'Translucent' blend mode. However, as you can see from the pictures in my previous comment, simply changing the blend mode from Mask to Translucent results in quite different appearances. Is there any way to make these two blend modes look the same?

By the way, I would love to submit a PR about this feature once I resolve these minor issues. I'm open to discussing this further if anyone has ideas.