Optimize meshes with meshoptimizer library if available

CMakeLists.txt

@@ -245,6 +245,14 @@ endif()
 find_package(Freetype REQUIRED)
 link_libraries(Freetype::Freetype)
 
+find_package(meshoptimizer CONFIG QUIET)
+if(meshoptimizer_FOUND)
+  message(STATUS "Found meshoptimizer library")
+  set(HAVE_MESHOPTIMIZER 1)
+else()
+  message(STATUS "meshoptimizer library is missing")
+endif()
+
 #[[
 get_cmake_property(_variableNames VARIABLES)
 list (SORT _variableNames)

config.h.in

@@ -3,4 +3,5 @@
 #cmakedefine HAVE_FLOAT_CHARCONV
 #cmakedefine HAVE_STD_FILESYSTEM
 #cmakedefine HAVE_WORDEXP
+#cmakedefine HAVE_MESHOPTIMIZER
 #cmakedefine WORDS_BIGENDIAN

src/celestia/CMakeLists.txt

@@ -80,6 +80,10 @@ if(ENABLE_FFMPEG)
   target_link_libraries(celestia ${FFMPEG_LIBRARIES})
 endif()
 
+if (HAVE_MESHOPTIMIZER)
+  target_link_libraries(celestia PRIVATE meshoptimizer::meshoptimizer)
+endif()
+
 install(TARGETS celestia LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR} NAMELINK_SKIP)
 
 add_subdirectory(glut)

src/celmodel/mesh.cpp

@@ -16,6 +16,10 @@
 #include <utility>
 #include <celutil/logger.h>
 
+#ifdef HAVE_MESHOPTIMIZER
+#include <meshoptimizer.h>
+#endif
+
 #include "mesh.h"
 
 using celestia::util::GetLogger;
@@ -455,6 +459,21 @@ Mesh::mergePrimitiveGroups()
     groups = std::move(newGroups);
 }
 
+void
+Mesh::optimize()
+{
+#ifdef HAVE_MESHOPTIMIZER
+    if (groups.size() > 1)
+        return;
+
+    auto &g = groups.front();
+
+    meshopt_optimizeVertexCache(g.indices.data(), g.indices.data(), g.indices.size(), nVertices);
+    meshopt_optimizeOverdraw(g.indices.data(), g.indices.data(), g.indices.size(), reinterpret_cast<float*>(vertices.data()), nVertices, vertexDesc.strideBytes, 1.05f);
+    meshopt_optimizeVertexFetch(vertices.data(), g.indices.data(), g.indices.size(), vertices.data(), nVertices, vertexDesc.strideBytes);
+#endif
+}
+
 bool
 Mesh::pick(const Eigen::Vector3d& rayOrigin, const Eigen::Vector3d& rayDirection, PickResult* result) const
 {
@@ -769,4 +788,5 @@ Mesh::canMerge(const Mesh &other, const std::vector<Material> &materials) const
 
     return true;
 }
+
 } // end namespace cmod

src/celmodel/mesh.h

@@ -239,6 +239,7 @@ class Mesh
 
     void merge(const Mesh&);
     bool canMerge(const Mesh&, const std::vector<Material> &materials) const;
+    void optimize();
 
  private:
     PrimitiveGroup createLinePrimitiveGroup(bool lineStrip, const std::vector<Index32>& indices);

src/celmodel/model.cpp

@@ -318,7 +318,6 @@ Model::usesTextureType(TextureSemantic t) const
 }
 
 
-
 bool
 Model::OpacityComparator::operator()(const Mesh& a, const Mesh& b) const
 {
@@ -353,6 +352,9 @@ Model::sortMeshes(const MeshComparator& comparator)
         p.merge(meshes[i]);
     }
     GetLogger()->info("Merged similar meshes: {} -> {}.\n", meshes.size(), newMeshes.size());
+
+    for (auto &mesh : newMeshes)
+        mesh.optimize();
     meshes = std::move(newMeshes);
 }