Build a single giant mesh for every texture-lightmap group of surfaces. Greatly improves rendering performance.

Assets/Scripts/Modules/BrushModel.cs

@@ -47,10 +47,7 @@ public class BrushModel
                 var groupGO = new GameObject($"T{key.Item1}_L{key.Item2}");
                 groupGO.transform.SetParent(modelGO.transform);
 
-                for (int i = 0; i < group.Value.Count; ++i)
-                {
-                    CreateSurfaceMeshes(group.Value[i], $"{i}", groupGO);
-                }
+                CreateMeshFromSurfaces(group.Value, groupGO.name, groupGO);
             }
         }
     }
@@ -138,6 +135,51 @@ public class BrushModel
         }
     }
 
+    private void CreateMeshFromSurfaces(List<QSurface> surfaces, string key, GameObject parentGO)
+    {
+        tempVertices.Clear();
+        tempTextureUVs.Clear();
+        tempLightmapUVs.Clear();
+        tempIndices.Clear();
+
+        int vertOffset = 0;
+        
+        for (int surfIdx = 0; surfIdx < surfaces.Count; ++surfIdx)
+        {
+            foreach (var polyVerts in surfaces[surfIdx].GetPolygons())
+            {
+                for (int vertIdx = 0; vertIdx < polyVerts.Length; ++vertIdx)
+                {
+                    tempVertices.Add(polyVerts[vertIdx].position.ToVector3().ToUnity());
+                    tempTextureUVs.Add(polyVerts[vertIdx].textureUV.ToVector2());
+                    tempLightmapUVs.Add(polyVerts[vertIdx].lightmapUV.ToVector2());
+                }
+                
+                // Reconstruct triangle fan
+                for (ushort index = 2; index < polyVerts.Length; ++index)
+                {
+                    tempIndices.Add((ushort)vertOffset);
+                    tempIndices.Add((ushort)(vertOffset + index - 1));
+                    tempIndices.Add((ushort)(vertOffset + index));
+                }
+
+                vertOffset += polyVerts.Length;
+            }
+        }
+        
+        Mesh mesh = new Mesh();
+        mesh.name = $"Surfaces_{key}";
+        mesh.SetVertices(tempVertices);
+        mesh.SetUVs(0, tempTextureUVs);
+        mesh.SetUVs(1, tempLightmapUVs);
+        mesh.SetIndices(tempIndices, MeshTopology.Triangles, 0);
+        mesh.RecalculateNormals();
+        mesh.UploadMeshData(true);
+        meshes.Add(mesh);
+            
+        CreateMeshObject(mesh, parentGO);
+    }
+
     private void CreateMeshObject(Mesh mesh, GameObject parentGO)
     {
         var meshGO = new GameObject(mesh.name);