Fixed build warnings on MSVC14 x64 in some scene optimisations.

code/OptimizeGraph.cpp

@@ -230,7 +230,7 @@ void OptimizeGraphProcess::CollectNewChildren(aiNode* nd, std::list<aiNode*>& no
         else nd->mChildren = NULL;
     }
 
-    nd->mNumChildren = child_nodes.size();
+    nd->mNumChildren = static_cast<unsigned int>(child_nodes.size());
 
     aiNode** tmp = nd->mChildren;
     for (std::list<aiNode*>::iterator it = child_nodes.begin(); it != child_nodes.end(); ++it) {
@@ -238,7 +238,7 @@ void OptimizeGraphProcess::CollectNewChildren(aiNode* nd, std::list<aiNode*>& no
         node->mParent = nd;
     }
 
-    nodes_out += child_nodes.size();
+    nodes_out += static_cast<unsigned int>(child_nodes.size());
 }
 
 // ------------------------------------------------------------------------------------------------

code/OptimizeMeshes.cpp

@@ -145,7 +145,7 @@ void OptimizeMeshesProcess::Execute( aiScene* pScene)
     meshes.resize( 0 );
     ai_assert(output.size() <= num_old);
 
-    mScene->mNumMeshes = output.size();
+    mScene->mNumMeshes = static_cast<unsigned int>(output.size());
     std::copy(output.begin(),output.end(),mScene->mMeshes);
 
     if (output.size() != num_old) {
@@ -199,7 +199,7 @@ void OptimizeMeshesProcess::ProcessNode( aiNode* pNode)
             } else {
                 output.push_back(mScene->mMeshes[im]);
             }
-            im = output.size()-1;
+            im = static_cast<unsigned int>(output.size()-1);
         }
     }