2fda20e1db
The core issue was that the geometry batch cache (e.g. `MeshBatchCache` or `PointCloudBatchCache`) was dependent on the object. This is problematic when the the same geometry is used with multiple different objects because the cache can't be consistent with all of them. Fortunately, the only thing that was retrieved from the object was the number of material slots, so if that can be avoided we should be fine. We can't just use the number of material slots stored on the geometry because that may have no material slots but still has material indices which are overridden on the object level. The solution is to take make the number of materials for a geometry only dependent on the actual `material_index` attribute and not on the number of available slots. More specifically, we find the maximal referenced material index and handle that many materials. This number does not depend on how many material slots there are on the object, but it still allows the object to override materials slots that the mesh references. A downside is that the maximum material index has to be computed which often requires an iteration over the mesh. Fortunately, we can cache that quite easily and the computation can be done in parallel. Also we are probably able to eagerly update the material index in many cases when it's set instead of computing it lazily. That is not implemented in this patch though. The largest part of the patch is making the maximal material index easily available on all the geometry types. Besides that, the material API is slightly replaced and the drawing code now makes use of the updated API. Pull Request: https://projects.blender.org/blender/blender/pulls/133498
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