Geometry Nodes: take materials into account when joining geometries

Materials are now kept intact when using the Join Geometry node
or when realizing instaces.

1 files changed, 26 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/geometry_set_instances.cc b/source/blender/blenkernel/intern/geometry_set_instances.cc
index b6ee0337dbf..97892075eca 100644
--- a/source/blender/blenkernel/intern/geometry_set_instances.cc
+++ b/source/blender/blenkernel/intern/geometry_set_instances.cc
@@ -15,6 +15,7 @@
  */
 
 #include "BKE_geometry_set_instances.hh"
+#include "BKE_material.h"
 #include "BKE_mesh.h"
 #include "BKE_mesh_wrapper.h"
 #include "BKE_modifier.h"
@@ -361,6 +362,8 @@ static Mesh *join_mesh_topology_and_builtin_attributes(Span<GeometryInstanceGrou
   int64_t cd_dirty_poly = 0;
   int64_t cd_dirty_edge = 0;
   int64_t cd_dirty_loop = 0;
+  VectorSet<Material *> materials;
+
   for (const GeometryInstanceGroup &set_group : set_groups) {
     const GeometrySet &set = set_group.geometry_set;
     const int tot_transforms = set_group.transforms.size();
@@ -374,6 +377,10 @@ static Mesh *join_mesh_topology_and_builtin_attributes(Span<GeometryInstanceGrou
       cd_dirty_poly |= mesh.runtime.cd_dirty_poly;
       cd_dirty_edge |= mesh.runtime.cd_dirty_edge;
       cd_dirty_loop |= mesh.runtime.cd_dirty_loop;
+      for (const int slot_index : IndexRange(mesh.totcol)) {
+        Material *material = mesh.mat[slot_index];
+        materials.add(material);
+      }
     }
     if (convert_points_to_vertices && set.has_pointcloud()) {
       const PointCloud &pointcloud = *set.get_pointcloud_for_read();
@@ -396,6 +403,10 @@ static Mesh *join_mesh_topology_and_builtin_attributes(Span<GeometryInstanceGrou
       break;
     }
   }
+  for (const int i : IndexRange(materials.size())) {
+    Material *material = materials[i];
+    BKE_id_material_eval_assign(&new_mesh->id, i + 1, material);
+  }
   new_mesh->runtime.cd_dirty_vert = cd_dirty_vert;
   new_mesh->runtime.cd_dirty_poly = cd_dirty_poly;
   new_mesh->runtime.cd_dirty_edge = cd_dirty_edge;
@@ -409,6 +420,14 @@ static Mesh *join_mesh_topology_and_builtin_attributes(Span<GeometryInstanceGrou
     const GeometrySet &set = set_group.geometry_set;
     if (set.has_mesh()) {
       const Mesh &mesh = *set.get_mesh_for_read();
+
+      Array<int> material_index_map(mesh.totcol);
+      for (const int i : IndexRange(mesh.totcol)) {
+        Material *material = mesh.mat[i];
+        const int new_material_index = materials.index_of(material);
+        material_index_map[i] = new_material_index;
+      }
+
       for (const float4x4 &transform : set_group.transforms) {
         for (const int i : IndexRange(mesh.totvert)) {
           const MVert &old_vert = mesh.mvert[i];
@@ -438,6 +457,13 @@ static Mesh *join_mesh_topology_and_builtin_attributes(Span<GeometryInstanceGrou
           MPoly &new_poly = new_mesh->mpoly[poly_offset + i];
           new_poly = old_poly;
           new_poly.loopstart += loop_offset;
+          if (old_poly.mat_nr >= 0 && old_poly.mat_nr < mesh.totcol) {
+            new_poly.mat_nr = material_index_map[new_poly.mat_nr];
+          }
+          else {
+            /* The material index was invalid before. */
+            new_poly.mat_nr = 0;
+          }
         }
 
         vert_offset += mesh.totvert;