When to use more material slots?

Development Asset Creation
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Hello everyone,

I know how to make static mesh with more material slots to use in UE4 but it increases number of drawcalls. I also know I can use Substance or Quixel to make for example sword with wooden handle and metallic blade all using just one material. So why (when not using layered materials) would someone use two slots? I think it is only needed when you work with totally different mats like opaque and translucent or emmitive mats, I get it there cause then the whole blueprint changes, but am I missing something? Or is it just to save time when prototyping so you don’t need to texture everything?

Thanks

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  1. Different types of mats as you mentioned
  2. Easier to build and maintain materials. Few extra draw calls hardly matter for the player weapon for example.
  3. Reusing master mat (and modified instances between objects). To my understanding it’s far cheaper (production and render wise) to have say metal trim mat copied all over, rather have it as part of 20 other textures.
  4. Dynamic materials/swapping materials. E.g. you can have one of hundred mat instances going for the hilt. Doing this with masks increases both the build and shader complexity.
  5. LoD stuff
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How are meshes made with more than 1 material slot?

I’m rather new to Unreal, but in my perspective thus far, the materials editor allows for multiple textures and use of layers to produce lots of things. I don’t see how it would have to be different for multiple material slots in terms of draw calls. My understanding thus far, which is simple, is shader complexity is derived from how it interacts with lighting and rendering settings such as resolution and cull distance.