Mesh split, bogeys follow rails.

Wow. This commit is too big. It:

* splits obj loaded meshes into individual named objects.
* moves obj to mesh(es) code into new file obj.impl.cpp, removing the
  clutter from mesh
* removes Physical for providing the wrong level of abstraction
* bit of a hack to adjust loaded models to offset rail vehicle bogeys to
  0 centre, and then applies their calculated position to the mesh

All in all, quite a lot of mess... But the result is the rail vehicle
bogeys now follow the rails quite authentically.

1 files changed, 10 insertions, 1 deletions

diff --git a/gfx/models/obj.h b/gfx/models/obj.h
index 96c5e94..2921e34 100644
--- a/gfx/models/obj.h
+++ b/gfx/models/obj.h
@@ -11,6 +11,8 @@
 #include <memory>
 #include <vector>
 
+class Mesh;
+
 class ObjParser : yyFlexLexer {
 public:
 	explicit ObjParser(const std::filesystem::path & fileName) : ObjParser {std::make_unique<std::ifstream>(fileName)}
@@ -19,7 +21,9 @@ public:
 
 	explicit ObjParser(std::unique_ptr<std::istream> in) : yyFlexLexer(in.get())
 	{
+		assert(in);
 		ObjParser::yylex();
+		assert(in->good());
 	}
 
 	int yylex() override;
@@ -29,8 +33,13 @@ public:
 	std::vector<glm::vec3> normals;
 	using FaceElement = glm::vec<3, int>;
 	using Face = std::vector<FaceElement>;
-	std::vector<Face> faces;
+	using Faces = std::vector<Face>;
+	using Object = std::pair<std::string, Faces>;
+	std::vector<Object> objects;
 	glm::length_t axis {0};
+
+	using NamedMesh = std::pair<std::string, std::shared_ptr<const Mesh>>;
+	[[nodiscard]] std::vector<NamedMesh> createMeshes() const;
 };
 
 #endif