Multiple UV Channels

pkinnane · February 23, 2021, 11:50pm

Hi

Is it possible to get the multiple UV channel UV coordinates for a mesh which has it’s “Texture Mapping” → “Use multiple mapping channels” checkbox enabled please? I am using RhinoCommon Mesh.TextureCoordinates to get the coordinates.

Thanks

Paul

nathanletwory · February 24, 2021, 5:55am

If you’re not using the change queue mechanism you’ll have to query the RhinoObject the mesh is from for texture mapping channel ids RhinoObject.GetTextureChannels Method, then get each texture mapping separately RhinoObject.GetTextureMapping Method. Then for each mapping set the mapping to the mesh text coordinates Mesh.SetTextureCoordinates Method and get the texture ccordinates Mesh.TextureCoordinates Property for that mapping.

For a mesh from the change queue you get the mapping collection Mesh.Mapping Property, then do the same procedure: for each mapping set texture coordinates, then retrieve.

disclaimer: I am not 100% certain it works like this. I haven’t implemented support for multiple UV mappings in Rhino Cycles yet. But this is what I’d start with when I get to it soon-ish.

pkinnane · March 31, 2021, 10:08am

Thanks @nathanletwory - I will try this out when I get some time for R&D. I guess the downside to this approach is that the meshes need to be processed for each texture mapping method, so it is potentially slower than just processing once.

Paul

nathanletwory · March 31, 2021, 10:12am

Hi @pkinnane,

I’ve just recently finished this part in RhinoCycles. In my implementation the work starts here:

github.com

mcneel/RhinoCycles/blob/31c453f2403e7ce68243031fd8a0b551ffbead51/Database/ChangeDatabase.cs#L997


			var cmuvList = new List<float[]>();

			if (_renderEngine.CancelRender) return;
			// now convert UVs: from vertex indexed array to per face per vertex
			if (mappingCollection == null)
			{
				// Get texture coordinates and
				// flattens to a float array.
				HandleMeshTextureCoordinates(meshdata, findices, cmuvList);
			} else {
				foreach(var mapping in mappingCollection.Channels) {
					meshdata.SetTextureCoordinates(mapping.Mapping, mapping.Local, false);
					HandleMeshTextureCoordinates(meshdata, findices, cmuvList);
				}
			}

			var meshid = new Tuple<Guid, int>(meshguid, meshIndex);

			var crc = linearlightMatId==uint.MaxValue ? _objectShaderDatabase.FindRenderHashForMeshId(meshid) : linearlightMatId;
			if (crc == uint.MaxValue) crc = 0;
			if (_renderEngine.CancelRender) return;

So loop over each channel, set the texture coordinates, then read those freshly set coordinates.

pkinnane · March 31, 2021, 10:17am

Awesome - thanks @nathanletwory!