Implement WieldMeshSceneNode which improves wield mesh rendering

- Don't create and cache an extruded mesh for every (non-node) item.
  Instead use a single one per image resolution.

- For cubic nodes reuse a single wield mesh too

- Improve lighting of the wielded item

- Increase far value of wield mesh scene camera, fixes #1770

- Also includes some minor refactorings of Camera and GenericCAO.

src/wieldmesh.h

@@ -0,0 +1,71 @@
+/*
+Minetest
+Copyright (C) 2010-2014 celeron55, Perttu Ahola <celeron55@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#ifndef WIELDMESH_HEADER
+#define WIELDMESH_HEADER
+
+#include "irrlichttypes_extrabloated.h"
+#include <string>
+
+class ItemStack;
+class IGameDef;
+class ITextureSource;
+struct TileSpec;
+
+/*
+	Wield item scene node, renders the wield mesh of some item
+*/
+class WieldMeshSceneNode: public scene::ISceneNode
+{
+public:
+	WieldMeshSceneNode(scene::ISceneNode *parent, scene::ISceneManager *mgr,
+			s32 id = -1, bool lighting = false);
+	virtual ~WieldMeshSceneNode();
+
+	void setCube(const TileSpec tiles[6],
+			v3f wield_scale, ITextureSource *tsrc);
+	void setExtruded(const std::string &imagename,
+			v3f wield_scale, ITextureSource *tsrc);
+	void setItem(const ItemStack &item, IGameDef *gamedef);
+
+	// Sets the vertex color of the wield mesh.
+	// Must only be used if the constructor was called with lighting = false
+	void setColor(video::SColor color);
+
+	virtual void render();
+
+	virtual const core::aabbox3d<f32>& getBoundingBox() const
+	{ return m_bounding_box; }
+
+private:
+	void changeToMesh(scene::IMesh *mesh);
+
+	// Child scene node with the current wield mesh
+	scene::IMeshSceneNode *m_meshnode;
+
+	// True if EMF_LIGHTING should be enabled.
+	bool m_lighting;
+
+	// Bounding box culling is disabled for this type of scene node,
+	// so this variable is just required so we can implement
+	// getBoundingBox() and is set to an empty box.
+	core::aabbox3d<f32> m_bounding_box;
+};
+
+#endif