gltfpack: Fix triangle count computation for non-triangle meshes

This affected lines/points including debug meshes that simplification
debugging produces.

Author: zeux

gltf/gltfpack.cpp

@@ -87,12 +87,14 @@ static void printMeshStats(const std::vector<Mesh>& meshes, const char* name)
 	{
 		const Mesh& mesh = meshes[i];
 
-		mesh_triangles += mesh.indices.size() / 3;
+		size_t triangles = mesh.type == cgltf_primitive_type_triangles ? mesh.indices.size() / 3 : 0;
+
+		mesh_triangles += triangles;
 		mesh_vertices += mesh.streams.empty() ? 0 : mesh.streams[0].data.size();
 
 		size_t instances = std::max(size_t(1), mesh.nodes.size() + mesh.instances.size());
 
-		total_triangles += mesh.indices.size() / 3 * instances;
+		total_triangles += triangles * instances;
 		total_instances += instances;
 		total_draws += std::max(size_t(1), mesh.nodes.size());
 	}
@@ -199,9 +201,10 @@ static bool printReport(const char* path, const std::vector<BufferView>& views,
 	{
 		const Mesh& mesh = meshes[i];
 
+		size_t triangles = mesh.type == cgltf_primitive_type_triangles ? mesh.indices.size() / 3 : 0;
 		size_t instances = std::max(size_t(1), mesh.nodes.size() + mesh.instances.size());
 
-		total_triangles += mesh.indices.size() / 3 * instances;
+		total_triangles += triangles * instances;
 		total_instances += instances;
 		total_draws += std::max(size_t(1), mesh.nodes.size());
 	}