Hi! I made a 3D model using C4D's materials which are in Window -> Content Browser. But when I dragged the .c4d file to my unity project assets folder, all the materials are grey, there's no textures. Is there anyway to solve that problem? Thx!
Assuming there is no incompatibility with the formats you used for your textures, then try collecting the C4D project ("save project" in the file menu) which will make a new folder with the C4D file and any associated textures. Also, make sure you are using raster images not procedural textures. Procedurals do not export to Unity, as they are created at render time by C4D. (They are sort of like using shaders in Unity)
I can remember in c4d embeds textures - maybe you need to put your textures next to your mesh in your project folder (see paragraph about textures in http://unity3d.com/support/documentation/Manual/Meshes.html)
Make sure all the textures in cinema have unique names.
Also make sure that the projection is the right type. I normally use Cubic or UVW mapping.