koobas.hobune.stream
How do I calculate the UV's for a procedurally generated shape?
I'm creating a mesh via script, but apparently I need UV's.
So two questions I guess: 1 - do I actually need UV's if I'm just using a material and not a texture?
and 2 - how do I procedurally generate the UV's for an irregular shape? I have a feeling this is a very complex problem but I just don't know...
Question one makes more sense rewritten: "using a material without a texture." Either the material has no texture slot, or you leave it blank (in that case you may need to make UV's, but they can all be 0's.)
Either way, the only purpose of UVs is to say where the different colors on a texture should go. So, no different texture colors, means no need for a UV.
So can I just have an empty UV array or should it be the same length and the triangle list but filled with zero's?
If it does get mad about not having UVs, then use all 0's the same length as the vertex array.
An empty texture slot is really filled in by Unity with a tiny white texture. That's why diffuse shader, no texture, color=red works.
1 - no you shouldn't, just be sure to use a shader that doesn't expect a texture and you should be fine
2 - yes arbitrarily mapping UVs to a polygonal shape is a somewhat complex, but well known problem . You need to "unwrap' the shape and make a (mostly) topologically equivalent plane of polygons from it.
See http://forum.devmaster.net/t/uvw-unwrap-algorithms/21409
The UnityEditor namespace holds functionality to easily unwrap a mesh and generate UVs via scripting.
Have a look at UnityEditor.Unwrapping.GeneratePerTriangleUV(...) and UnityEditor.Unwrapping.GenerateSecondaryUVSet(...)
Remember, that these can only be used in the Unity editor and not runtime in your app/game.
