Does using assets with multi-uv channels affect performance?

melviso

Say u have a scene with all assets having like 5 uv channels each. Will this affect performance in ue4? What would be the better approach?

LTS3D

From a memory standpoint, you'll definitely have larger file sizes and larger memory chunks being allocated to meshes using several UV sets. From a performance standpoint, you'll have a higher vertex count if you have different UV shells across all those separate UV sets.

As for how to approach it, we need more information on what you're trying to achieve that would require so many UV sets before pointing out a best course of action.

melviso

Something like this:
https://3dtotal.com/tutorials/t/advanced-multi-channel-texturing-in-max-blood-knight-ziv-qual-character-male-human-warrior
Is there an advantage using this method over using many textures instead?

zachagreg

Hey Melviso, just to clarify whether or not you mean textures or materials in UE4. The page you linked still uses multiple textures each arrayed on different UV sets(UV channels). Implementation of that into UE4 would essentially equate to the same thing; multiple textures all blended into one material.

The flip side of that would be having multiple materials blended and layered onto the character both methods would in theory have the same amount of textures being used but you would also be using more Shader Switches for the mesh with 5 materials. I've been told before that the less materials, per mesh, the better. But I can be corrected on that.

Would you be creating just the one character for your UE scene? 

You can have multiple materials with one UV set. You can have multiple UV sets with one material. Or you can use material instancing and layering within in UE4. So it comes down to what you would want to do with your character. As making your character with unique UV unwraps and say one or two textures is going to be best for pure performance I believe. However, if you're wanting to create a system with color palette swaps or armor changes, something that would change the materials or be used on multiple characters the other approaches would have more re-usability.

melviso

@zachagreg Thanks for the info. I am currently experimenting with the workflow. Saves a lot of time and gets things done easier with this workflow :- )