Material's in GLTF files

[SpiderPig]

So, I've been thinking.  I have about 10 different pine tree models in GLTF format.  Different sizes and styles etc.  They all use the same base textures, DIFFUSE and NORMAL maps.  My question is if I load all 10 pine trees are 10 unique materials being created?  One for each tree?

[Josh]

14 hours ago, SpiderPig said:

So, I've been thinking.  I have about 10 different pine tree models in GLTF format.  Different sizes and styles etc.  They all use the same base textures, DIFFUSE and NORMAL maps.  My question is if I load all 10 pine trees are 10 unique materials being created?  One for each tree?

Yes, each material will be unique, but it doesn't really matter. Rendering is grouped by shader family. The material is just a small structure stored in memory. Each mesh stores an index to the material, and its looked up in the shader itself, so it really has no effect on the performance of the rendering code.

[SpiderPig]

I was more curious about reaching the max material limit.  But if we can change that to somthing big it may not matter.  

[Josh]

I think that buffer gets dynamically resized, so it doesn't even matter if you hit the initial limit.

The texture arrays on the other hand are fixed size, because they are declared in the shaders.

[SpiderPig]

Ah nice   That's good to know, I've just been wondering how to structure files so they don't duplicate textures.

[Josh]

If you have multiple materials referencing the same texture, it’s still just one texture

[SpiderPig]

I did have all of the tree objects separated into different folders based on size, so when I saved them through the asset editor it copied all the textures over to each folder.  So in that case it would have double ups.  I can solve it by moving everything that shares textures into the same folder but it just means I have 100+ files in one folder.  I just like to organizes things so I can find files easily.

[SpiderPig]

So in the asset editor when browsing for an existing material it will copy the material into the GLTF file and copy textures into the same directory as the GLTF.  I wonder if browsing for an existing material should just store the file path to the material instead.  I would like that better because if I want to change a material parameter for the pine tree, currently I'd have to do it for each model.  I'd rather just change the material file itself once and have it work for everything that uses it.

Would it be possible to make the GLTF file do this?

[Josh]

glTF files do not store external materials. I could add the material path in the "extras" info but it would create a discontinuity where Ultra would be loading external materials, but every modeling application would be loading something different. I think this would cause more problems than it solves.

glTF files CAN store textures in different paths, but in practice this is never done, and it would always be relative to the glTF file itself, not to the project. So you would end up with a lot of paths like "../../Nature/rock.dds" which I think would be prone to breakage.

[SpiderPig]

Yeah I agree.  Best to leave it as it is as it's fine in most cases.  I'll work something out.