How do I assign different materials to complex shaped textures in a object?

I was designing a sneaker and usually when I design sneakers the mesh only has one material. But now I want to assign a different material for each texture but the shapes are to complex to select. Is this possible, if so please tell me how. Thank you.

Attachments




make all the materials you need. create mask textures for each material, and use them to join the different materials in the node editor.