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, 5 insertions, 5 deletions

diff --git a/gfx/models/obj.ll b/gfx/models/obj.ll
index 9329a5a..a9a857b 100644
--- a/gfx/models/obj.ll
+++ b/gfx/models/obj.ll
@@ -43,8 +43,8 @@ falsey (0|off)
 }
 <INITIAL>"f " {
   BEGIN(FACE);
-  faces.emplace_back();
-  faces.back().emplace_back();
+  objects.back().second.emplace_back();
+  objects.back().second.back().emplace_back();
   axis = 0;
 }
 <INITIAL>"mtllib " {
@@ -81,7 +81,7 @@ falsey (0|off)
   // fprintf(stderr, "MTLLIB <%s>\n", YYText());
 }
 <OBJECT>{linestring} {
-  // fprintf(stderr, "OBJECT <%s>\n", YYText());
+  objects.emplace_back(YYText(), Faces{});
 }
 <SMOOTH>{truthy} {
   // fprintf(stderr, "Set smooth\n");
@@ -99,13 +99,13 @@ falsey (0|off)
   texCoords.back()[axis++] = std::stof(YYText());
 }
 <FACE>{index} {
-  faces.back().back()[axis] = std::stoi(YYText());
+  objects.back().second.back().back()[axis] = std::stoi(YYText());
 }
 <FACE>\/ {
   axis++;
 }
 <FACE>[ \t] {
-  faces.back().emplace_back();
+  objects.back().second.back().emplace_back();
   axis = 0;
 }