Add macOS support to C4D importer (#5516)

The latest Cineware SDK explicitly asserts macOS support in its
documentation, but Assimp's C4D importer only works with Windows MSVC
targets. Let's improve its portability by refactoring importer code to
not depend on MSVC-only data types and quirks, and add support for linking
against the universal macOS static libraries provided in the Cineware
SDK.

Note that the C4D importer still cannot support Linux platforms because
Maxon does not provide the necessary precompiled Cineware libraries for
that platform. Windows MinGW targets are also out of the question as the
MinGW toolchain uses compiled libraries in a different format.

Co-authored-by: Kim Kulling <kimkulling@users.noreply.github.com>

CMakeLists.txt

@@ -563,9 +563,9 @@ SET ( ASSIMP_BUILD_NONFREE_C4D_IMPORTER OFF CACHE BOOL
 )
 
 IF (ASSIMP_BUILD_NONFREE_C4D_IMPORTER)
-  IF ( MSVC )
   SET(C4D_INCLUDES "${CMAKE_CURRENT_SOURCE_DIR}/contrib/Cineware/includes")
 
+  IF (WIN32)
     # pick the correct prebuilt library
     IF(MSVC143)
       SET(C4D_LIB_POSTFIX "_2022")
@@ -583,7 +583,7 @@ IF (ASSIMP_BUILD_NONFREE_C4D_IMPORTER)
       SET(C4D_LIB_POSTFIX "_2010")
     ELSE()
       MESSAGE( FATAL_ERROR
-        "C4D is currently only supported with MSVC 10, 11, 12, 14, 14.2, 14.3"
+        "C4D for Windows is currently only supported with MSVC 10, 11, 12, 14, 14.2, 14.3"
       )
     ENDIF()
 
@@ -601,9 +601,20 @@ IF (ASSIMP_BUILD_NONFREE_C4D_IMPORTER)
     # winsock and winmm are necessary (and undocumented) dependencies of Cineware SDK because
     # it can be used to communicate with a running Cinema 4D instance
     SET(C4D_EXTRA_LIBRARIES WSock32.lib Winmm.lib)
+  ELSEIF (APPLE)
+    SET(C4D_LIB_BASE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/contrib/Cineware/libraries/osx")
+
+    SET(C4D_DEBUG_LIBRARIES
+      "${C4D_LIB_BASE_PATH}/debug/libcinewarelib.a"
+      "${C4D_LIB_BASE_PATH}/debug/libjpeglib.a"
+    )
+    SET(C4D_RELEASE_LIBRARIES
+      "${C4D_LIB_BASE_PATH}/release/libcinewarelib.a"
+      "${C4D_LIB_BASE_PATH}/release/libjpeglib.a"
+    )
   ELSE ()
     MESSAGE( FATAL_ERROR
-      "C4D is currently only available on Windows with Cineware SDK installed in contrib/Cineware"
+      "C4D is currently only available on Windows and macOS with Cineware SDK installed in contrib/Cineware"
     )
   ENDIF ()
 ELSE ()

code/AssetLib/C4D/C4DImporter.cpp

@@ -46,10 +46,6 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 // no #ifdefing here, Cinema4D support is carried out in a branch of assimp
 // where it is turned on in the CMake settings.
 
-#ifndef _MSC_VER
-#   error C4D support is currently MSVC only
-#endif
-
 #include "C4DImporter.h"
 #include <memory>
 #include <assimp/IOSystem.hpp>
@@ -111,7 +107,7 @@ C4DImporter::C4DImporter() = default;
 C4DImporter::~C4DImporter() = default;
 
 // ------------------------------------------------------------------------------------------------
-bool C4DImporter::CanRead( const std::string& pFile, IOSystem* /*pIOHandler*/, bool /*checkSig*/) const {
+bool C4DImporter::CanRead( const std::string& pFile, IOSystem* pIOHandler, bool checkSig) const {
     const std::string& extension = GetExtension(pFile);
     if (extension == "c4d") {
         return true;
@@ -305,7 +301,7 @@ void C4DImporter::RecurseHierarchy(BaseObject* object, aiNode* parent) {
 
     // based on Cineware sample code
     while (object) {
-        const LONG type = object->GetType();
+        const Int32 type = object->GetType();
         const Matrix& ml = object->GetMl();
 
         aiNode* const nd = new aiNode();
@@ -368,8 +364,8 @@ aiMesh* C4DImporter::ReadMesh(BaseObject* object) {
     PolygonObject* const polyObject = dynamic_cast<PolygonObject*>(object);
     ai_assert(polyObject != nullptr);
 
-    const LONG pointCount = polyObject->GetPointCount();
+    const Int32 pointCount = polyObject->GetPointCount();
-    const LONG polyCount = polyObject->GetPolygonCount();
+    const Int32 polyCount = polyObject->GetPolygonCount();
     if(!polyObject || !pointCount) {
         LogWarn("ignoring mesh with zero vertices or faces");
         return nullptr;
@@ -391,7 +387,7 @@ aiMesh* C4DImporter::ReadMesh(BaseObject* object) {
     unsigned int vcount = 0;
 
     // first count vertices
-    for (LONG i = 0; i < polyCount; i++)
+    for (Int32 i = 0; i < polyCount; i++)
     {
         vcount += 3;
 
@@ -434,7 +430,7 @@ aiMesh* C4DImporter::ReadMesh(BaseObject* object) {
     }
 
     // copy vertices and extra channels over and populate faces
-    for (LONG i = 0; i < polyCount; ++i, ++face) {
+    for (Int32 i = 0; i < polyCount; ++i, ++face) {
         ai_assert(polys[i].a < pointCount && polys[i].a >= 0);
         const Vector& pointA = points[polys[i].a];
         verts->x = pointA.x;
@@ -511,7 +507,7 @@ aiMesh* C4DImporter::ReadMesh(BaseObject* object) {
         if (tangents_src) {
 
             for(unsigned int k = 0; k < face->mNumIndices; ++k) {
-                LONG l;
+                Int32 l;
                 switch(k) {
                 case 0:
                     l = polys[i].a;

code/AssetLib/C4D/C4DImporter.h

@@ -78,6 +78,8 @@ namespace Assimp  {
 // -------------------------------------------------------------------------------------------
 class C4DImporter : public BaseImporter, public LogFunctions<C4DImporter> {
 public:
+    C4DImporter();
+    ~C4DImporter() override;
     bool CanRead( const std::string& pFile, IOSystem*, bool checkSig) const override;
 
 protected: