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, 36 insertions, 0 deletions

diff --git a/gfx/models/obj.impl.cpp b/gfx/models/obj.impl.cpp
new file mode 100644
index 0000000..e410058
--- /dev/null
+++ b/gfx/models/obj.impl.cpp
@@ -0,0 +1,36 @@
+#include "obj.h"
+#include <gfx/models/mesh.h>
+#include <gfx/models/vertex.hpp>
+
+std::vector<ObjParser::NamedMesh>
+ObjParser::createMeshes() const
+{
+	std::vector<ObjParser::NamedMesh> out;
+	out.reserve(objects.size());
+	for (const auto & obj : objects) {
+		std::vector<Vertex> overtices;
+		std::vector<ObjParser::FaceElement> vertexOrder;
+		std::vector<unsigned int> indices;
+		for (const auto & face : obj.second) {
+			for (auto idx = 2U; idx < face.size(); idx += 1) {
+				auto f = [&](auto idx) {
+					const auto & fe {face[idx]};
+					if (const auto existing = std::find(vertexOrder.begin(), vertexOrder.end(), fe);
+							existing != vertexOrder.end()) {
+						indices.push_back(std::distance(vertexOrder.begin(), existing));
+					}
+					else {
+						indices.push_back(overtices.size());
+						overtices.emplace_back(vertices[fe.x - 1], texCoords[fe.y - 1], -normals[fe.z - 1]);
+						vertexOrder.emplace_back(fe);
+					}
+				};
+				f(0);
+				f(idx);
+				f(idx - 1);
+			}
+		}
+		out.emplace_back(obj.first, std::make_shared<Mesh>(overtices, indices));
+	}
+	return out;
+}