From Drederic Bouvier, "I noticed the AC3D loader resets database path given as Options,

preventing users to put textures in another directory. This patch adds
the model path to the path list instead of replacing it."

src/osgPlugins/ac/ac3d.cpp

@@ -98,7 +98,7 @@ class ReaderWriterAC : public osgDB::ReaderWriter
                 local_opt = static_cast<Options*>(options->clone(osg::CopyOp::DEEP_COPY_ALL));
             else
                 local_opt = new Options;
-            local_opt->setDatabasePath(osgDB::getFilePath(fileName));
+            local_opt->getDatabasePathList().push_back(osgDB::getFilePath(fileName));
 
             ReadResult result = readNode(fin, local_opt.get());
             if (result.validNode())