I’m currently learning 3D modelling and such, and I just had a question. If you are using 1 UV Map for different parts of an object that have different textures for them, would it still be possible to make changes with the shader for that one part?
For example, lets say I make a table, the legs are metal and the top part is wood, I have a wood texture and a metal texture into one texture map, could I make the metal texture shiny while keeping the wood texture normal? Or would I need to use 2 different UV maps and have 2 separate textures?
So, just to make sure I understand this. Make the model and UV map it in maya or whatever 3D modelling tool you use and then assign the texture in UE4? No need to worry about textures in Maya?
If you want your entire model to use one material that has both wood and metal, you would need a texture map (or an alpha channel of your main texture) that specifies which areas of the model are metallic or not.
If you want two separate materials on your model, one wood and one metal, you would assign two different materials inside of Maya. By giving your model two different materials, like two plain Lambert shaders, those material slots will be saved in Unreal Engine and you can fill them with whatever material you want there. I recommend unchecking the “Import Materials” and “Import Textures” boxes upon import so you can assign things from scratch and see what’s going on.
You first need to UV your model properly, then you can texture it in photoshop (Substance Designer and Quixel suite can also help on the texturing process, but i recommend you to use photoshop if you are new to texturing). Paint on the UV islands of your model and save that texture with a size of power of 2 (512,1024,2048, etc) To mask parts of the model you want them to be metallic you can use an Alpha channel like StephaBon said or make a different texture using each channel to separate your model parts.
You can have different objects (with different material for each) sharing same texture. For instance, you can clamp all parts of say a car into a single texture map as long as you space them out nicely, even though wheels & body are separate objects. Just assign the same texture to different materials.
You can have same object (but different material for various part) share same texture map, either via elements (Easiest, but provided you can separate them via mesh) or layered materials (via masking).
The tricky part is lightmap. As far as I know (Someone correct me if I am wrong), is that you cannot share same Lightmap on different objects. In fact, I think a light map is craete for every static mesh in the scene.
So, your car will have its own lightmap texture, each wheel will have its own lightmap texture. So if your wheels take up 1/4 of UV space, the 3/4 will be wasted space for lightmap. The solution is to create a separate light map (use a new UV index), in a way that the wheel fill the UV space better. In 4.5, this process can be automated.