Merge branch 'master' into feature/material-nodes

README.md

@@ -24,6 +24,8 @@ More in-depth information about the features of the add-on are available on the
 
 You can refer to the [Installation & Update Guide](https://github.com/mitsuba-renderer/mitsuba-blender/wiki/Installation-&-Update-Guide) on the wiki for more detailed instructions.
 
-### Requirements
+### Supported versions
 
-* `Blender >= 2.93`
+Blender version should be at least `2.93`. The addon has been extensively tested
+on LTS versions of blender (`2.93`, `3.3`). We recommend using those whenever
+possible.

mitsuba-blender/exporter/geometry.py

@@ -1,9 +1,10 @@
-from .materials import export_material
-from .export_context import Files
-from mathutils import Matrix
 import os
 import bpy
 
+from .materials import export_material
+from .export_context import Files
+
+
 def convert_mesh(export_ctx, b_mesh, matrix_world, name, mat_nr):
     '''
     This method creates a mitsuba mesh from a blender mesh and returns it.
@@ -86,28 +87,44 @@ def export_object(deg_instance, export_ctx, is_particle):
         else:
             transform = b_object.matrix_world
 
+
         if mat_count == 0: # No assigned material
-            converted_parts.append((-1, convert_mesh(export_ctx,
-                                                    b_mesh,
-                                                    transform,
-                                                    name_clean,
-                                                    0)))
-        for mat_nr in range(mat_count):
-            if b_mesh.materials[mat_nr]:
+            converted_parts.append((
+                name_clean,
+                -1,
+                convert_mesh(export_ctx, b_mesh, transform, name_clean, 0)
+            ))
+        else:
+            refs_per_mat = {}
+            for mat_nr in range(mat_count):
+                mat = b_mesh.materials[mat_nr]
+                if not mat:
+                    continue
+
+                # Ensures that the exported mesh parts have unique names,
+                # even if multiple material slots refer to the same material.
+                n_mat_refs = refs_per_mat.get(mat.name, 0)
+                name = f'{name_clean}-{mat.name}'
+
+                if n_mat_refs >= 1:
+                    name += f'-{n_mat_refs:03d}'
+
                 mts_mesh = convert_mesh(export_ctx,
                                         b_mesh,
                                         transform,
-                                        f"{name_clean}-{b_mesh.materials[mat_nr].name}",
+                                        name,
                                         mat_nr)
                 if mts_mesh is not None and mts_mesh.face_count() > 0:
-                    converted_parts.append((mat_nr, mts_mesh))
-                    b_mat = b_mesh.materials[mat_nr]
-                    export_material(export_ctx, b_mat)
+                    converted_parts.append((name, mat_nr, mts_mesh))
+                    refs_per_mat[mat.name] = n_mat_refs + 1
+
+                    if n_mat_refs == 0:
+                        # Only export this material once
+                        export_material(export_ctx, mat)
 
         if b_object.type != 'MESH':
             b_object.to_mesh_clear()
 
-        part_count = len(converted_parts)
         # Use a ShapeGroup for instances and split meshes
         use_shapegroup = is_instance or is_instance_emitter or is_particle
         # TODO: Check if shapegroups for split meshes is worth it
@@ -116,12 +133,8 @@ def export_object(deg_instance, export_ctx, is_particle):
                 'type': 'shapegroup'
             }
 
-        for (mat_nr, mts_mesh) in converted_parts:
-            # Determine the file name
-            if part_count == 1:
-                name = f"{name_clean}"
-            else:
-                name = f"{name_clean}-{b_mesh.materials[mat_nr].name}"
+        for (name, mat_nr, mts_mesh) in converted_parts:
+            name = name_clean if len(converted_parts) == 1 else name
             mesh_id = f"mesh-{name}"
 
             # Save as binary ply

mitsuba-blender/importer/bl_import_ply.py

@@ -300,7 +300,9 @@ def load_ply_mesh(filepath, ply_name):
     def add_face(vertices, indices, uvindices, colindices):
         mesh_faces.append(indices)
         if uvindices:
-            mesh_uvs.extend([(vertices[index][uvindices[0]], vertices[index][uvindices[1]]) for index in indices])
+            # Mitsuba seems to flip the UVS on the y-axis when exporting. We account for this here by flipping them
+            # back to the original coordinates.
+            mesh_uvs.extend([(vertices[index][uvindices[0]], 1-vertices[index][uvindices[1]]) for index in indices])
         if colindices:
             if len(colindices) == 3:
                 mesh_colors.extend([