assimp/code/ColladaExporter.cpp

/*
Open Asset Import Library (assimp)
----------------------------------------------------------------------

Copyright (c) 2006-2012, assimp team
All rights reserved.

Redistribution and use of this software in source and binary forms, 
with or without modification, are permitted provided that the 
following conditions are met:

* Redistributions of source code must retain the above
  copyright notice, this list of conditions and the
  following disclaimer.

* Redistributions in binary form must reproduce the above
  copyright notice, this list of conditions and the
  following disclaimer in the documentation and/or other
  materials provided with the distribution.

* Neither the name of the assimp team, nor the names of its
  contributors may be used to endorse or promote products
  derived from this software without specific prior
  written permission of the assimp team.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

----------------------------------------------------------------------
*/

#include "AssimpPCH.h"

#ifndef ASSIMP_BUILD_NO_EXPORT
#ifndef ASSIMP_BUILD_NO_COLLADA_EXPORTER
#include "ColladaExporter.h"

#include "Bitmap.h"
#include "fast_atof.h"
#include "SceneCombiner.h" 
#include "XMLTools.h"

#include <ctime>
#include <set>

using namespace Assimp;

namespace Assimp
{

// ------------------------------------------------------------------------------------------------
// Worker function for exporting a scene to Collada. Prototyped and registered in Exporter.cpp
void ExportSceneCollada(const char* pFile, IOSystem* pIOSystem, const aiScene* pScene)
{
	std::string path = "";
	std::string file = pFile;

	// We need to test both types of folder separators because pIOSystem->getOsSeparator() is not reliable.
	// Moreover, the path given by some applications is not even consistent with the OS specific type of separator.
	const char* end_path = std::max(strrchr(pFile, '\\'), strrchr(pFile, '/'));

	if(end_path != NULL) {
		path = std::string(pFile, end_path + 1 - pFile);
		file = file.substr(end_path + 1 - pFile, file.npos);

		std::size_t pos = file.find_last_of('.');
		if(pos != file.npos) {
			file = file.substr(0, pos);
		}
	}

	// invoke the exporter 
	ColladaExporter iDoTheExportThing( pScene, pIOSystem, path, file);

	// we're still here - export successfully completed. Write result to the given IOSYstem
	boost::scoped_ptr<IOStream> outfile (pIOSystem->Open(pFile,"wt"));
	if(outfile == NULL) {
		throw DeadlyExportError("could not open output .dae file: " + std::string(pFile));
	}

	// XXX maybe use a small wrapper around IOStream that behaves like std::stringstream in order to avoid the extra copy.
	outfile->Write( iDoTheExportThing.mOutput.str().c_str(), static_cast<size_t>(iDoTheExportThing.mOutput.tellp()),1);
}

} // end of namespace Assimp



// ------------------------------------------------------------------------------------------------
// Constructor for a specific scene to export
ColladaExporter::ColladaExporter( const aiScene* pScene, IOSystem* pIOSystem, const std::string& path, const std::string& file) : mIOSystem(pIOSystem), mPath(path), mFile(file)
{
	// make sure that all formatting happens using the standard, C locale and not the user's current locale
	mOutput.imbue( std::locale("C") );

	mScene = pScene;
	mSceneOwned = false;

	// set up strings
	endstr = "\n"; 

	// start writing
	WriteFile();
}

// ------------------------------------------------------------------------------------------------
// Destructor
ColladaExporter::~ColladaExporter()
{
	if(mSceneOwned) {
		delete mScene;
	}
}

// ------------------------------------------------------------------------------------------------
// Starts writing the contents
void ColladaExporter::WriteFile()
{
	// write the DTD
	mOutput << "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?>" << endstr;
	// COLLADA element start
	mOutput << "<COLLADA xmlns=\"http://www.collada.org/2005/11/COLLADASchema\" version=\"1.4.1\">" << endstr;
	PushTag();

	WriteTextures();
	WriteHeader();

	WriteMaterials();
	WriteGeometryLibrary();

	WriteSceneLibrary();

	// useless Collada fu at the end, just in case we haven't had enough indirections, yet. 
	mOutput << startstr << "<scene>" << endstr;
	PushTag();
	mOutput << startstr << "<instance_visual_scene url=\"#" + XMLEscape(mScene->mRootNode->mName.C_Str()) + "\" />" << endstr;
	PopTag();
	mOutput << startstr << "</scene>" << endstr;
	PopTag();
	mOutput << "</COLLADA>" << endstr;
}

// ------------------------------------------------------------------------------------------------
// Writes the asset header
void ColladaExporter::WriteHeader()
{
	static const float epsilon = 0.00001f;
	static const aiQuaternion x_rot(aiMatrix3x3( 
		0, -1,  0,
		1,  0,  0,
		0,  0,  1));
	static const aiQuaternion y_rot(aiMatrix3x3(
		1,  0,  0,
		0,  1,  0,
		0,  0,  1));
	static const aiQuaternion z_rot(aiMatrix3x3(
		1,  0,  0,
		0,  0,  1,
		0, -1,  0));

	static const unsigned int date_nb_chars = 20;
	char date_str[date_nb_chars];
	std::time_t date = std::time(NULL);
	std::strftime(date_str, date_nb_chars, "%Y-%m-%dT%H:%M:%S", std::localtime(&date));

	std::string scene_name = mScene->mRootNode->mName.C_Str();

	aiVector3D scaling;
	aiQuaternion rotation;
	aiVector3D position;
	mScene->mRootNode->mTransformation.Decompose(scaling, rotation, position);
	rotation.Normalize();

	bool add_root_node = false;

	float scale = 1.0;
	if(std::abs(scaling.x - scaling.y) <= epsilon && std::abs(scaling.x - scaling.z) <= epsilon && std::abs(scaling.y - scaling.z) <= epsilon) {
		scale = (float) ((((double) scaling.x) + ((double) scaling.y) + ((double) scaling.z)) / 3.0);
	} else {
		add_root_node = true;
	}

	std::string up_axis = "Y_UP";
	if(rotation.Equal(x_rot, epsilon)) {
		up_axis = "X_UP";
	} else if(rotation.Equal(y_rot, epsilon)) {
		up_axis = "Y_UP";
	} else if(rotation.Equal(z_rot, epsilon)) {
		up_axis = "Z_UP";
	} else {
		add_root_node = true;
	}

	if(! position.Equal(aiVector3D(0, 0, 0))) {
		add_root_node = true;
	}

	if(mScene->mRootNode->mNumChildren == 0) {
		add_root_node = true;
	}

	if(add_root_node) {
		aiScene* scene;
		SceneCombiner::CopyScene(&scene, mScene);

		aiNode* root = new aiNode("Scene");

		root->mNumChildren = 1;
		root->mChildren = new aiNode*[root->mNumChildren];

		root->mChildren[0] = scene->mRootNode;
		scene->mRootNode->mParent = root;
		scene->mRootNode = root;

		mScene = scene;
		mSceneOwned = true;

		up_axis = "Y_UP";
		scale = 1.0;
	}

	mOutput << startstr << "<asset>" << endstr;
	PushTag();
	mOutput << startstr << "<contributor>" << endstr;
	PushTag();

	aiMetadata* meta = mScene->mRootNode->mMetaData;
	aiString value;
	if (!meta || !meta->Get("Author", value))		
		mOutput << startstr << "<author>" << "Assimp" << "</author>" << endstr;
	else		
		mOutput << startstr << "<author>" << XMLEscape(value.C_Str()) << "</author>" << endstr;

	if (!meta || !meta->Get("AuthoringTool", value))
		mOutput << startstr << "<authoring_tool>" << "Assimp Exporter" << "</authoring_tool>" << endstr;
	else		
		mOutput << startstr << "<authoring_tool>" << XMLEscape(value.C_Str()) << "</authoring_tool>" << endstr;

	//mOutput << startstr << "<author>" << mScene->author.C_Str() << "</author>" << endstr;
	//mOutput << startstr << "<authoring_tool>" << mScene->authoringTool.C_Str() << "</authoring_tool>" << endstr;
	
	PopTag();
	mOutput << startstr << "</contributor>" << endstr;
	mOutput << startstr << "<created>" << date_str << "</created>" << endstr;
	mOutput << startstr << "<modified>" << date_str << "</modified>" << endstr;
	mOutput << startstr << "<unit name=\"meter\" meter=\"" << scale << "\" />" << endstr;
	mOutput << startstr << "<up_axis>" << up_axis << "</up_axis>" << endstr;
	PopTag();
	mOutput << startstr << "</asset>" << endstr;
}

// ------------------------------------------------------------------------------------------------
// Write the embedded textures
void ColladaExporter::WriteTextures() {
	static const unsigned int buffer_size = 1024;
	char str[buffer_size];

	if(mScene->HasTextures()) {
		for(unsigned int i = 0; i < mScene->mNumTextures; i++) {
			// It would be great to be able to create a directory in portable standard C++, but it's not the case,
			// so we just write the textures in the current directory.

			aiTexture* texture = mScene->mTextures[i];

			ASSIMP_itoa10(str, buffer_size, i + 1);

			std::string name = mFile + "_texture_" + (i < 1000 ? "0" : "") + (i < 100 ? "0" : "") + (i < 10 ? "0" : "") + str + "." + ((const char*) texture->achFormatHint);

			boost::scoped_ptr<IOStream> outfile(mIOSystem->Open(mPath + name, "wb"));
			if(outfile == NULL) {
				throw DeadlyExportError("could not open output texture file: " + mPath + name);
			}

			if(texture->mHeight == 0) {
				outfile->Write((void*) texture->pcData, texture->mWidth, 1);
			} else {
				Bitmap::Save(texture, outfile.get());
			}

			outfile->Flush();

			textures.insert(std::make_pair(i, name));
		}
	}
}

// ------------------------------------------------------------------------------------------------
// Reads a single surface entry from the given material keys
void ColladaExporter::ReadMaterialSurface( Surface& poSurface, const aiMaterial* pSrcMat, aiTextureType pTexture, const char* pKey, size_t pType, size_t pIndex)
{
  if( pSrcMat->GetTextureCount( pTexture) > 0 )
  {
    aiString texfile;
    unsigned int uvChannel = 0;
    pSrcMat->GetTexture( pTexture, 0, &texfile, NULL, &uvChannel);

    std::string index_str(texfile.C_Str());

    if(index_str.size() != 0 && index_str[0] == '*')
    {
		unsigned int index;

    	index_str = index_str.substr(1, std::string::npos);

    	try {
    		index = (unsigned int) strtoul10_64(index_str.c_str());
    	} catch(std::exception& error) {
    		throw DeadlyExportError(error.what());
    	}

    	std::map<unsigned int, std::string>::const_iterator name = textures.find(index);

    	if(name != textures.end()) {
    		poSurface.texture = name->second;
    	} else {
    		throw DeadlyExportError("could not find embedded texture at index " + index_str);
    	}
    } else
    {
		poSurface.texture = texfile.C_Str();
    }

    poSurface.channel = uvChannel;
	poSurface.exist = true;
  } else
  {
    if( pKey )
      poSurface.exist = pSrcMat->Get( pKey, pType, pIndex, poSurface.color) == aiReturn_SUCCESS;
  }
}

// ------------------------------------------------------------------------------------------------
// Writes an image entry for the given surface
void ColladaExporter::WriteImageEntry( const Surface& pSurface, const std::string& pNameAdd)
{
  if( !pSurface.texture.empty() )
  {
    mOutput << startstr << "<image id=\"" << XMLEscape(pNameAdd) << "\">" << endstr;
    PushTag(); 
    mOutput << startstr << "<init_from>";
	
	// URL encode image file name first, then XML encode on top
	std::stringstream imageUrlEncoded;
    for( std::string::const_iterator it = pSurface.texture.begin(); it != pSurface.texture.end(); ++it )
    {
      if( isalnum( *it) || *it == '_' || *it == '.' || *it == '/' || *it == '\\' )
        imageUrlEncoded << *it;
      else
        imageUrlEncoded << '%' << std::hex << size_t( (unsigned char) *it) << std::dec;
    }
	mOutput << XMLEscape(imageUrlEncoded.str());
    mOutput << "</init_from>" << endstr;
    PopTag();
    mOutput << startstr << "</image>" << endstr;
  }
}

// ------------------------------------------------------------------------------------------------
// Writes a color-or-texture entry into an effect definition
void ColladaExporter::WriteTextureColorEntry( const Surface& pSurface, const std::string& pTypeName, const std::string& pImageName)
{
  if(pSurface.exist) {
    mOutput << startstr << "<" << pTypeName << ">" << endstr;
    PushTag();
    if( pSurface.texture.empty() )
    {
      mOutput << startstr << "<color sid=\"" << pTypeName << "\">" << pSurface.color.r << "   " << pSurface.color.g << "   " << pSurface.color.b << "   " << pSurface.color.a << "</color>" << endstr;
    }
	else
    {
      mOutput << startstr << "<texture texture=\"" << XMLEscape(pImageName) << "\" texcoord=\"CHANNEL" << pSurface.channel << "\" />" << endstr;
    }
    PopTag();
    mOutput << startstr << "</" << pTypeName << ">" << endstr;
  }
}

// ------------------------------------------------------------------------------------------------
// Writes the two parameters necessary for referencing a texture in an effect entry
void ColladaExporter::WriteTextureParamEntry( const Surface& pSurface, const std::string& pTypeName, const std::string& pMatName)
{
  // if surface is a texture, write out the sampler and the surface parameters necessary to reference the texture
  if( !pSurface.texture.empty() )
  {
    mOutput << startstr << "<newparam sid=\"" << XMLEscape(pMatName) << "-" << pTypeName << "-surface\">" << endstr;
    PushTag();
    mOutput << startstr << "<surface type=\"2D\">" << endstr;
    PushTag();
    mOutput << startstr << "<init_from>" << XMLEscape(pMatName) << "-" << pTypeName << "-image</init_from>" << endstr;
    PopTag();
    mOutput << startstr << "</surface>" << endstr;
    PopTag();
    mOutput << startstr << "</newparam>" << endstr;

    mOutput << startstr << "<newparam sid=\"" << XMLEscape(pMatName) << "-" << pTypeName << "-sampler\">" << endstr;
    PushTag();
    mOutput << startstr << "<sampler2D>" << endstr;
    PushTag();
    mOutput << startstr << "<source>" << XMLEscape(pMatName) << "-" << pTypeName << "-surface</source>" << endstr;
    PopTag();
    mOutput << startstr << "</sampler2D>" << endstr;
    PopTag();
    mOutput << startstr << "</newparam>" << endstr;
  }
}

// ------------------------------------------------------------------------------------------------
// Writes a scalar property
void ColladaExporter::WriteFloatEntry( const Property& pProperty, const std::string& pTypeName)
{
	if(pProperty.exist) {
		mOutput << startstr << "<" << pTypeName << ">" << endstr;
		PushTag();
		mOutput << startstr << "<float sid=\"" << pTypeName << "\">" << pProperty.value << "</float>" << endstr;
		PopTag();
		mOutput << startstr << "</" << pTypeName << ">" << endstr;
	}
}

// ------------------------------------------------------------------------------------------------
// Writes the material setup
void ColladaExporter::WriteMaterials()
{
  materials.resize( mScene->mNumMaterials);

  std::set<std::string> material_names;

  /// collect all materials from the scene
  size_t numTextures = 0;
  for( size_t a = 0; a < mScene->mNumMaterials; ++a )
  {
    const aiMaterial* mat = mScene->mMaterials[a];

    aiString name;
    if( mat->Get( AI_MATKEY_NAME, name) != aiReturn_SUCCESS )
      name = "mat";
    materials[a].name = std::string( "m") + boost::lexical_cast<std::string> (a) + name.C_Str();
    for( std::string::iterator it = materials[a].name.begin(); it != materials[a].name.end(); ++it ) {
		// isalnum on MSVC asserts for code points outside [0,255]. Thus prevent unwanted promotion
		// of char to signed int and take the unsigned char value.
      if( !isalnum( static_cast<uint8_t>(*it) ) ) {
        *it = '_';
	  }
	}

	aiShadingMode shading = aiShadingMode_Flat;
	materials[a].shading_model = "phong";
	if(mat->Get( AI_MATKEY_SHADING_MODEL, shading) == aiReturn_SUCCESS) {
		if(shading == aiShadingMode_Phong) {
			materials[a].shading_model = "phong";
		} else if(shading == aiShadingMode_Blinn) {
			materials[a].shading_model = "blinn";
		} else if(shading == aiShadingMode_NoShading) {
			materials[a].shading_model = "constant";
		} else if(shading == aiShadingMode_Gouraud) {
			materials[a].shading_model = "lambert";
		}
	}

    ReadMaterialSurface( materials[a].ambient, mat, aiTextureType_AMBIENT, AI_MATKEY_COLOR_AMBIENT);
    if( !materials[a].ambient.texture.empty() ) numTextures++;
    ReadMaterialSurface( materials[a].diffuse, mat, aiTextureType_DIFFUSE, AI_MATKEY_COLOR_DIFFUSE);
    if( !materials[a].diffuse.texture.empty() ) numTextures++;
    ReadMaterialSurface( materials[a].specular, mat, aiTextureType_SPECULAR, AI_MATKEY_COLOR_SPECULAR);
    if( !materials[a].specular.texture.empty() ) numTextures++;
    ReadMaterialSurface( materials[a].emissive, mat, aiTextureType_EMISSIVE, AI_MATKEY_COLOR_EMISSIVE);
    if( !materials[a].emissive.texture.empty() ) numTextures++;
    ReadMaterialSurface( materials[a].reflective, mat, aiTextureType_REFLECTION, AI_MATKEY_COLOR_REFLECTIVE);
    if( !materials[a].reflective.texture.empty() ) numTextures++;
	ReadMaterialSurface( materials[a].transparent, mat, aiTextureType_OPACITY, AI_MATKEY_COLOR_TRANSPARENT);
    if( !materials[a].transparent.texture.empty() ) numTextures++;
    ReadMaterialSurface( materials[a].normal, mat, aiTextureType_NORMALS, NULL, 0, 0);
    if( !materials[a].normal.texture.empty() ) numTextures++;

	materials[a].shininess.exist = mat->Get( AI_MATKEY_SHININESS, materials[a].shininess.value) == aiReturn_SUCCESS;
	materials[a].transparency.exist = mat->Get( AI_MATKEY_OPACITY, materials[a].transparency.value) == aiReturn_SUCCESS;
	materials[a].transparency.value = 1 - materials[a].transparency.value;
	materials[a].index_refraction.exist = mat->Get( AI_MATKEY_REFRACTI, materials[a].index_refraction.value) == aiReturn_SUCCESS;
  }

  // output textures if present
  if( numTextures > 0 )
  {
    mOutput << startstr << "<library_images>" << endstr; 
    PushTag();
    for( std::vector<Material>::const_iterator it = materials.begin(); it != materials.end(); ++it )
    { 
      const Material& mat = *it;
      WriteImageEntry( mat.ambient, mat.name + "-ambient-image");
      WriteImageEntry( mat.diffuse, mat.name + "-diffuse-image");
      WriteImageEntry( mat.specular, mat.name + "-specular-image");
      WriteImageEntry( mat.emissive, mat.name + "-emission-image");
      WriteImageEntry( mat.reflective, mat.name + "-reflective-image");
	  WriteImageEntry( mat.transparent, mat.name + "-transparent-image");
      WriteImageEntry( mat.normal, mat.name + "-normal-image");
    }
    PopTag();
    mOutput << startstr << "</library_images>" << endstr;
  }

  // output effects - those are the actual carriers of information
  if( !materials.empty() )
  {
    mOutput << startstr << "<library_effects>" << endstr;
    PushTag();
    for( std::vector<Material>::const_iterator it = materials.begin(); it != materials.end(); ++it )
    {
      const Material& mat = *it;
      // this is so ridiculous it must be right
      mOutput << startstr << "<effect id=\"" << XMLEscape(mat.name) << "-fx\" name=\"" << XMLEscape(mat.name) << "\">" << endstr;
      PushTag();
      mOutput << startstr << "<profile_COMMON>" << endstr;
      PushTag();

      // write sampler- and surface params for the texture entries
      WriteTextureParamEntry( mat.emissive, "emission", mat.name);
      WriteTextureParamEntry( mat.ambient, "ambient", mat.name);
      WriteTextureParamEntry( mat.diffuse, "diffuse", mat.name);
      WriteTextureParamEntry( mat.specular, "specular", mat.name);
      WriteTextureParamEntry( mat.reflective, "reflective", mat.name);
	  WriteTextureParamEntry( mat.transparent, "transparent", mat.name);
	  WriteTextureParamEntry( mat.normal, "normal", mat.name);

      mOutput << startstr << "<technique sid=\"standard\">" << endstr;
      PushTag();
	  mOutput << startstr << "<" << mat.shading_model << ">" << endstr;
      PushTag();

      WriteTextureColorEntry( mat.emissive, "emission", mat.name + "-emission-sampler");
      WriteTextureColorEntry( mat.ambient, "ambient", mat.name + "-ambient-sampler");
      WriteTextureColorEntry( mat.diffuse, "diffuse", mat.name + "-diffuse-sampler");
      WriteTextureColorEntry( mat.specular, "specular", mat.name + "-specular-sampler");
	  WriteFloatEntry(mat.shininess, "shininess");
      WriteTextureColorEntry( mat.reflective, "reflective", mat.name + "-reflective-sampler");
	  WriteTextureColorEntry( mat.transparent, "transparent", mat.name + "-transparent-sampler");
	  WriteFloatEntry(mat.transparency, "transparency");
	  WriteFloatEntry(mat.index_refraction, "index_of_refraction");

	  if(! mat.normal.texture.empty()) {
		WriteTextureColorEntry( mat.normal, "bump", mat.name + "-normal-sampler");
	  }

      PopTag();
      mOutput << startstr << "</" << mat.shading_model << ">" << endstr;
      PopTag();
      mOutput << startstr << "</technique>" << endstr;
      PopTag();
      mOutput << startstr << "</profile_COMMON>" << endstr;
      PopTag();
      mOutput << startstr << "</effect>" << endstr;
    }
    PopTag();
    mOutput << startstr << "</library_effects>" << endstr;

    // write materials - they're just effect references
    mOutput << startstr << "<library_materials>" << endstr;
    PushTag();
    for( std::vector<Material>::const_iterator it = materials.begin(); it != materials.end(); ++it )
    {
      const Material& mat = *it;
      mOutput << startstr << "<material id=\"" << XMLEscape(mat.name) << "\" name=\"" << mat.name << "\">" << endstr;
      PushTag();
      mOutput << startstr << "<instance_effect url=\"#" << XMLEscape(mat.name) << "-fx\"/>" << endstr;
      PopTag();
      mOutput << startstr << "</material>" << endstr;
    }
    PopTag();
    mOutput << startstr << "</library_materials>" << endstr;
  }
}

// ------------------------------------------------------------------------------------------------
// Writes the geometry library
void ColladaExporter::WriteGeometryLibrary()
{
	mOutput << startstr << "<library_geometries>" << endstr;
	PushTag();

	for( size_t a = 0; a < mScene->mNumMeshes; ++a)
		WriteGeometry( a);

	PopTag();
	mOutput << startstr << "</library_geometries>" << endstr;
}

// ------------------------------------------------------------------------------------------------
// Writes the given mesh
void ColladaExporter::WriteGeometry( size_t pIndex)
{
	const aiMesh* mesh = mScene->mMeshes[pIndex];
	const std::string idstr = GetMeshId( pIndex);
	const std::string idstrEscaped = XMLEscape(idstr);

  if( mesh->mNumFaces == 0 || mesh->mNumVertices == 0 )
    return;

	// opening tag
	mOutput << startstr << "<geometry id=\"" << idstrEscaped << "\" name=\"" << idstrEscaped << "_name\" >" << endstr;
	PushTag();

	mOutput << startstr << "<mesh>" << endstr;
	PushTag();

	// Positions
	WriteFloatArray( idstr + "-positions", FloatType_Vector, (float*) mesh->mVertices, mesh->mNumVertices);
	// Normals, if any
	if( mesh->HasNormals() )
		WriteFloatArray( idstr + "-normals", FloatType_Vector, (float*) mesh->mNormals, mesh->mNumVertices);

	// texture coords
	for( size_t a = 0; a < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++a)
	{
		if( mesh->HasTextureCoords( a) )
		{
			WriteFloatArray( idstr + "-tex" + boost::lexical_cast<std::string> (a), mesh->mNumUVComponents[a] == 3 ? FloatType_TexCoord3 : FloatType_TexCoord2,
				(float*) mesh->mTextureCoords[a], mesh->mNumVertices);
		}
	}

	// vertex colors
	for( size_t a = 0; a < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++a)
	{
		if( mesh->HasVertexColors( a) )
			WriteFloatArray( idstr + "-color" + boost::lexical_cast<std::string> (a), FloatType_Color, (float*) mesh->mColors[a], mesh->mNumVertices);
	}

	// assemble vertex structure
	mOutput << startstr << "<vertices id=\"" << idstrEscaped << "-vertices" << "\">" << endstr;
	PushTag();
	mOutput << startstr << "<input semantic=\"POSITION\" source=\"#" << idstrEscaped << "-positions\" />" << endstr;
	if( mesh->HasNormals() )
		mOutput << startstr << "<input semantic=\"NORMAL\" source=\"#" << idstrEscaped << "-normals\" />" << endstr;
	for( size_t a = 0; a < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++a )
	{
		if( mesh->HasTextureCoords( a) )
			mOutput << startstr << "<input semantic=\"TEXCOORD\" source=\"#" << idstrEscaped << "-tex" << a << "\" " /*<< "set=\"" << a << "\"" */ << " />" << endstr;
	}
	for( size_t a = 0; a < AI_MAX_NUMBER_OF_COLOR_SETS; ++a )
	{
		if( mesh->HasVertexColors( a) )
			mOutput << startstr << "<input semantic=\"COLOR\" source=\"#" << idstrEscaped << "-color" << a << "\" " /*<< set=\"" << a << "\"" */ << " />" << endstr;
	}
	
	PopTag();
	mOutput << startstr << "</vertices>" << endstr;

	// count the number of lines, triangles and polygon meshes
	int countLines = 0;
	int countPoly = 0;
	for( size_t a = 0; a < mesh->mNumFaces; ++a )
	{
		if (mesh->mFaces[a].mNumIndices == 2) countLines++;
		else if (mesh->mFaces[a].mNumIndices >= 3) countPoly++;
	}

	// lines
	if (countLines)
	{
		mOutput << startstr << "<lines count=\"" << countLines << "\" material=\"defaultMaterial\">" << endstr;
		PushTag();
		mOutput << startstr << "<input offset=\"0\" semantic=\"VERTEX\" source=\"#" << idstrEscaped << "-vertices\" />" << endstr;
		mOutput << startstr << "<p>";
		for( size_t a = 0; a < mesh->mNumFaces; ++a )
		{
			const aiFace& face = mesh->mFaces[a];
			if (face.mNumIndices != 2) continue;
			for( size_t b = 0; b < face.mNumIndices; ++b )
				mOutput << face.mIndices[b] << " ";
		}
		mOutput << "</p>" << endstr;
		PopTag();
		mOutput << startstr << "</lines>" << endstr;
	}

	// triangle - dont use it, because compatibility problems

	// polygons
	if (countPoly)
	{		
		mOutput << startstr << "<polylist count=\"" << countPoly << "\" material=\"defaultMaterial\">" << endstr;
		PushTag();
		mOutput << startstr << "<input offset=\"0\" semantic=\"VERTEX\" source=\"#" << idstrEscaped << "-vertices\" />" << endstr;
	
		mOutput << startstr << "<vcount>";
		for( size_t a = 0; a < mesh->mNumFaces; ++a )
		{
			if (mesh->mFaces[a].mNumIndices < 3) continue;
			mOutput << mesh->mFaces[a].mNumIndices << " ";
		}
		mOutput << "</vcount>" << endstr;
	
		mOutput << startstr << "<p>";
		for( size_t a = 0; a < mesh->mNumFaces; ++a )
		{
			const aiFace& face = mesh->mFaces[a];
			if (face.mNumIndices < 3) continue;
			for( size_t b = 0; b < face.mNumIndices; ++b )
				mOutput << face.mIndices[b] << " ";
		}
		mOutput << "</p>" << endstr;
		PopTag();
		mOutput << startstr << "</polylist>" << endstr;
	}

	// closing tags
	PopTag();
	mOutput << startstr << "</mesh>" << endstr;
	PopTag();
	mOutput << startstr << "</geometry>" << endstr;
}

// ------------------------------------------------------------------------------------------------
// Writes a float array of the given type
void ColladaExporter::WriteFloatArray( const std::string& pIdString, FloatDataType pType, const float* pData, size_t pElementCount)
{
	size_t floatsPerElement = 0;
	switch( pType )
	{
		case FloatType_Vector: floatsPerElement = 3; break;
		case FloatType_TexCoord2: floatsPerElement = 2; break;
		case FloatType_TexCoord3: floatsPerElement = 3; break;
		case FloatType_Color: floatsPerElement = 3; break;
		default:
			return;
	}

	std::string arrayId = pIdString + "-array";

	mOutput << startstr << "<source id=\"" << XMLEscape(pIdString) << "\" name=\"" << XMLEscape(pIdString) << "\">" << endstr;
	PushTag();

	// source array
	mOutput << startstr << "<float_array id=\"" << XMLEscape(arrayId) << "\" count=\"" << pElementCount * floatsPerElement << "\"> ";
	PushTag();

	if( pType == FloatType_TexCoord2 )
	{
		for( size_t a = 0; a < pElementCount; ++a )
		{
			mOutput << pData[a*3+0] << " ";
			mOutput << pData[a*3+1] << " ";
		}
	} 
	else if( pType == FloatType_Color )
	{
		for( size_t a = 0; a < pElementCount; ++a )
		{
			mOutput << pData[a*4+0] << " ";
			mOutput << pData[a*4+1] << " ";
			mOutput << pData[a*4+2] << " ";
		}
	}
	else
	{
		for( size_t a = 0; a < pElementCount * floatsPerElement; ++a )
			mOutput << pData[a] << " ";
	}
	mOutput << "</float_array>" << endstr; 
	PopTag();

	// the usual Collada fun. Let's bloat it even more!
	mOutput << startstr << "<technique_common>" << endstr;
	PushTag();
	mOutput << startstr << "<accessor count=\"" << pElementCount << "\" offset=\"0\" source=\"#" << arrayId << "\" stride=\"" << floatsPerElement << "\">" << endstr;
	PushTag();

	switch( pType )
	{
		case FloatType_Vector:
			mOutput << startstr << "<param name=\"X\" type=\"float\" />" << endstr;
			mOutput << startstr << "<param name=\"Y\" type=\"float\" />" << endstr;
			mOutput << startstr << "<param name=\"Z\" type=\"float\" />" << endstr;
			break;

		case FloatType_TexCoord2:
			mOutput << startstr << "<param name=\"S\" type=\"float\" />" << endstr;
			mOutput << startstr << "<param name=\"T\" type=\"float\" />" << endstr;
			break;

		case FloatType_TexCoord3:
			mOutput << startstr << "<param name=\"S\" type=\"float\" />" << endstr;
			mOutput << startstr << "<param name=\"T\" type=\"float\" />" << endstr;
			mOutput << startstr << "<param name=\"P\" type=\"float\" />" << endstr;
			break;

		case FloatType_Color:
			mOutput << startstr << "<param name=\"R\" type=\"float\" />" << endstr;
			mOutput << startstr << "<param name=\"G\" type=\"float\" />" << endstr;
			mOutput << startstr << "<param name=\"B\" type=\"float\" />" << endstr;
			break;
	}

	PopTag();
	mOutput << startstr << "</accessor>" << endstr;
	PopTag();
	mOutput << startstr << "</technique_common>" << endstr;
	PopTag();
	mOutput << startstr << "</source>" << endstr;
}

// ------------------------------------------------------------------------------------------------
// Writes the scene library
void ColladaExporter::WriteSceneLibrary()
{
	const std::string scene_name_escaped = XMLEscape(mScene->mRootNode->mName.C_Str());

	mOutput << startstr << "<library_visual_scenes>" << endstr;
	PushTag();
	mOutput << startstr << "<visual_scene id=\"" + scene_name_escaped + "\" name=\"" + scene_name_escaped + "\">" << endstr;
	PushTag();

	// start recursive write at the root node
	for( size_t a = 0; a < mScene->mRootNode->mNumChildren; ++a )
		WriteNode( mScene->mRootNode->mChildren[a]);

	PopTag();
	mOutput << startstr << "</visual_scene>" << endstr;
	PopTag();
	mOutput << startstr << "</library_visual_scenes>" << endstr;
}

// ------------------------------------------------------------------------------------------------
// Recursively writes the given node
void ColladaExporter::WriteNode(aiNode* pNode)
{
	// the must have a name
	if (pNode->mName.length == 0)
	{		
		std::stringstream ss;
		ss << "Node_" << pNode;
		pNode->mName.Set(ss.str());
	}

	const std::string node_name_escaped = XMLEscape(pNode->mName.data);
	mOutput << startstr << "<node id=\"" << node_name_escaped << "\" name=\"" << node_name_escaped << "\">" << endstr;
	PushTag();

	// write transformation - we can directly put the matrix there
	// TODO: (thom) decompose into scale - rot - quad to allow adressing it by animations afterwards
	const aiMatrix4x4& mat = pNode->mTransformation;
	mOutput << startstr << "<matrix>";
	mOutput << mat.a1 << " " << mat.a2 << " " << mat.a3 << " " << mat.a4 << " ";
	mOutput << mat.b1 << " " << mat.b2 << " " << mat.b3 << " " << mat.b4 << " ";
	mOutput << mat.c1 << " " << mat.c2 << " " << mat.c3 << " " << mat.c4 << " ";
	mOutput << mat.d1 << " " << mat.d2 << " " << mat.d3 << " " << mat.d4;
	mOutput << "</matrix>" << endstr;

	// instance every geometry
	for( size_t a = 0; a < pNode->mNumMeshes; ++a )
	{
		const aiMesh* mesh = mScene->mMeshes[pNode->mMeshes[a]];
	// do not instanciate mesh if empty. I wonder how this could happen
	if( mesh->mNumFaces == 0 || mesh->mNumVertices == 0 )
		continue;

		mOutput << startstr << "<instance_geometry url=\"#" << XMLEscape(GetMeshId( pNode->mMeshes[a])) << "\">" << endstr;
		PushTag();
	mOutput << startstr << "<bind_material>" << endstr;
	PushTag();
	mOutput << startstr << "<technique_common>" << endstr;
	PushTag();
	mOutput << startstr << "<instance_material symbol=\"defaultMaterial\" target=\"#" << XMLEscape(materials[mesh->mMaterialIndex].name) << "\" />" << endstr;
		PopTag();
	mOutput << startstr << "</technique_common>" << endstr;
	PopTag();
	mOutput << startstr << "</bind_material>" << endstr;
	PopTag();
		mOutput << startstr << "</instance_geometry>" << endstr;
	}

	// recurse into subnodes
	for( size_t a = 0; a < pNode->mNumChildren; ++a )
		WriteNode( pNode->mChildren[a]);

	PopTag();
	mOutput << startstr << "</node>" << endstr;
}

#endif
#endif