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, 6 insertions, 4 deletions

diff --git a/game/vehicles/vehicle.h b/game/vehicles/vehicle.h
index 25ed5bb..945d43b 100644
--- a/game/vehicles/vehicle.h
+++ b/game/vehicles/vehicle.h
@@ -1,9 +1,9 @@
 #ifndef VEHICLE_H
 #define VEHICLE_H
 
-#include "game/physical.h"
 #include <game/network/link.h>
 #include <game/worldobject.h>
+#include <gfx/renderable.h>
 #include <memory>
 #include <string>
 #include <utility>
@@ -22,12 +22,14 @@ private:
 	float totalLen {0.F};
 };
 
-class Vehicle : public WorldObject, public Physical {
+class Vehicle : public WorldObject, public Renderable {
 public:
-	Vehicle(const LinkPtr & link, const std::string & obj, const std::string & tex);
-	float linkDist {0}; // distance long current link
+	Vehicle(const LinkPtr & link, float linkDist = 0);
+	float linkDist; // distance long current link
 	float speed {50}; // speed in m/s (~75 km/h)
 
+	Transform location;
+
 protected:
 	LinkHistory linkHist;
 };