StdMeshLoaderXml.cpp

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/*
 * OpenClonk, http://www.openclonk.org
 *
 * Copyright (c) 2001-2009, RedWolf Design GmbH, http://www.clonk.de/
 * Copyright (c) 2009-2016, The OpenClonk Team and contributors
 *
 * Distributed under the terms of the ISC license; see accompanying file
 * "COPYING" for details.
 *
 * "Clonk" is a registered trademark of Matthes Bender, used with permission.
 * See accompanying file "TRADEMARK" for details.
 *
 * To redistribute this file separately, substitute the full license texts
 * for the above references.
 */
 
// A loader for the OGRE .mesh XML file format
 
#include "C4Include.h"
#include "lib/StdMesh.h"
#include "lib/StdMeshLoader.h"
#include <tinyxml.h>
 
// Helper class to load things from an XML file with error checking
class StdMeshLoader::StdMeshXML
{
public:
    StdMeshXML(const char* filename, const char* xml_data);
 
    const char* RequireStrAttribute(TiXmlElement* element, const char* attribute) const;
    int RequireIntAttribute(TiXmlElement* element, const char* attribute) const;
    float RequireFloatAttribute(TiXmlElement* element, const char* attribute) const;
 
    TiXmlElement* RequireFirstChild(TiXmlElement* element, const char* child);
 
    void LoadGeometry(StdMesh& mesh, std::vector<StdSubMesh::Vertex>& vertices, TiXmlElement* boneassignments_elem);
    void LoadBoneAssignments(StdMesh& mesh, std::vector<StdSubMesh::Vertex>& vertices, TiXmlElement* boneassignments_elem);
 
    void Error(const StdStrBuf& message, TiXmlElement* element) const;
    void Error(const StdStrBuf& message, int row) const;
 
private:
    TiXmlDocument Document;
    StdStrBuf FileName;
};
 
StdMeshLoader::StdMeshXML::StdMeshXML(const char* filename, const char* xml_data):
        FileName(filename)
{
    Document.Parse(xml_data);
    if (Document.Error())
        Error(StdStrBuf(Document.ErrorDesc()), Document.ErrorRow());
}
 
const char* StdMeshLoader::StdMeshXML::RequireStrAttribute(TiXmlElement* element, const char* attribute) const
{
    const char* value = element->Attribute(attribute);
    if (!value) Error(FormatString("Element '%s' does not have attribute '%s'", element->Value(), attribute), element);
    return value;
}
 
int StdMeshLoader::StdMeshXML::RequireIntAttribute(TiXmlElement* element, const char* attribute) const
{
    int retval;
    if (element->QueryIntAttribute(attribute, &retval) != TIXML_SUCCESS)
        Error(FormatString("Element '%s' does not have integer attribute '%s'", element->Value(), attribute), element);
    return retval;
}
 
float StdMeshLoader::StdMeshXML::RequireFloatAttribute(TiXmlElement* element, const char* attribute) const
{
    float retval = 0;
    if (element->QueryFloatAttribute(attribute, &retval) != TIXML_SUCCESS)
        Error(FormatString("Element '%s' does not have floating point attribute '%s'", element->Value(), attribute), element);
    return retval;
}
 
TiXmlElement* StdMeshLoader::StdMeshXML::RequireFirstChild(TiXmlElement* element, const char* child)
{
    TiXmlElement* retval;
 
    if (element)
    {
        retval = element->FirstChildElement(child);
        if (!retval)
            Error(FormatString("Element '%s' does not contain '%s' child", element->Value(), child), element);
    }
    else
    {
        retval = Document.RootElement();
        if (strcmp(retval->Value(), child) != 0)
            Error(FormatString("Root element is not '%s'", child), retval);
    }
 
    return retval;
}
 
void StdMeshLoader::StdMeshXML::Error(const StdStrBuf& message, TiXmlElement* element) const
{
    Error(message, element->Row());
}
 
void StdMeshLoader::StdMeshXML::Error(const StdStrBuf& message, int row) const
{
    throw StdMeshLoader::LoaderException(FormatString("%s:%u: %s", FileName.getData(), row, message.getData()).getData());
}
 
void StdMeshLoader::StdMeshXML::LoadGeometry(StdMesh& mesh, std::vector<StdSubMesh::Vertex>& vertices, TiXmlElement* geometry_elem)
{
    // Check whether mesh has any vertices so far -- we need this later for
    // initialization of bounding box and bounding sphere.
    bool hasVertices = false;
    if(!mesh.SharedVertices.empty()) hasVertices = true;
    for(auto & SubMesh : mesh.SubMeshes)
        if(!SubMesh.Vertices.empty())
            hasVertices = true;
 
    int VertexCount = RequireIntAttribute(geometry_elem, "vertexcount");
    vertices.resize(VertexCount);
 
    static const unsigned int POSITIONS = 1;
    static const unsigned int NORMALS = 2;
    static const unsigned int TEXCOORDS = 4;
 
    // Individual vertex attributes can be split up in multiple vertex buffers
    unsigned int loaded_attributes = 0;
    for(TiXmlElement* buffer_elem = geometry_elem->FirstChildElement("vertexbuffer"); buffer_elem != nullptr; buffer_elem = buffer_elem->NextSiblingElement("vertexbuffer"))
    {
        unsigned int attributes = 0;
        if(buffer_elem->Attribute("positions")) attributes |= POSITIONS;
        if(buffer_elem->Attribute("normals")) attributes |= NORMALS;
        if(buffer_elem->Attribute("texture_coords")) attributes |= TEXCOORDS;
 
        unsigned int i;
        TiXmlElement* vertex_elem;
        for (vertex_elem = buffer_elem->FirstChildElement("vertex"), i = 0; vertex_elem != nullptr && i < vertices.size(); vertex_elem = vertex_elem->NextSiblingElement("vertex"), ++i)
        {
            if(attributes & POSITIONS)
            {
                TiXmlElement* position_elem = RequireFirstChild(vertex_elem, "position");
 
                vertices[i].x = RequireFloatAttribute(position_elem, "x");
                vertices[i].y = RequireFloatAttribute(position_elem, "y");
                vertices[i].z = RequireFloatAttribute(position_elem, "z");
            }
 
            if(attributes & NORMALS)
            {
                TiXmlElement* normal_elem = RequireFirstChild(vertex_elem, "normal");
 
                vertices[i].nx = RequireFloatAttribute(normal_elem, "x");
                vertices[i].ny = RequireFloatAttribute(normal_elem, "y");
                vertices[i].nz = RequireFloatAttribute(normal_elem, "z");
            }
 
            if(attributes & TEXCOORDS)
            {
                // FIXME: The Ogre format supports denoting multiple texture coordinates, but the rendering code only supports one
                // currently only the first set is read, any additional ones are ignored
                TiXmlElement* texcoord_elem = RequireFirstChild(vertex_elem, "texcoord");
                vertices[i].u = RequireFloatAttribute(texcoord_elem, "u");
                vertices[i].v = RequireFloatAttribute(texcoord_elem, "v");
            }
 
            vertices[i] = OgreToClonk::TransformVertex(vertices[i]);
 
            if (attributes & POSITIONS)
            {
                const float d = std::sqrt(vertices[i].x*vertices[i].x
                                        + vertices[i].y*vertices[i].y
                                        + vertices[i].z*vertices[i].z);
 
                // Construct BoundingBox
                StdMeshBox& BoundingBox = mesh.BoundingBox;
                if (i == 0 && !hasVertices)
                {
                    // First vertex
                    BoundingBox.x1 = BoundingBox.x2 = vertices[i].x;
                    BoundingBox.y1 = BoundingBox.y2 = vertices[i].y;
                    BoundingBox.z1 = BoundingBox.z2 = vertices[i].z;
                    mesh.BoundingRadius = d;
                }
                else
                {
                    BoundingBox.x1 = std::min(vertices[i].x, BoundingBox.x1);
                    BoundingBox.x2 = std::max(vertices[i].x, BoundingBox.x2);
                    BoundingBox.y1 = std::min(vertices[i].y, BoundingBox.y1);
                    BoundingBox.y2 = std::max(vertices[i].y, BoundingBox.y2);
                    BoundingBox.z1 = std::min(vertices[i].z, BoundingBox.z1);
                    BoundingBox.z2 = std::max(vertices[i].z, BoundingBox.z2);
                    mesh.BoundingRadius = std::max(mesh.BoundingRadius, d);
                }
            }
        }
 
        if(vertex_elem != nullptr)
            Error(FormatString("Too many vertices in vertexbuffer"), buffer_elem);
        if(i < vertices.size())
            Error(FormatString("Not enough vertices in vertexbuffer"), buffer_elem);
 
        loaded_attributes |= attributes;
    }
 
    static const unsigned int REQUIRED_ATTRIBUTES = POSITIONS | NORMALS | TEXCOORDS;
    if((loaded_attributes & REQUIRED_ATTRIBUTES) != REQUIRED_ATTRIBUTES)
        Error(FormatString("Not all required vertex attributes (positions, normals, texcoords) present in mesh geometry"), geometry_elem);
}
 
void StdMeshLoader::StdMeshXML::LoadBoneAssignments(StdMesh& mesh, std::vector<StdSubMesh::Vertex>& vertices, TiXmlElement* boneassignments_elem)
{
    for (TiXmlElement* vertexboneassignment_elem = boneassignments_elem->FirstChildElement("vertexboneassignment"); vertexboneassignment_elem != nullptr; vertexboneassignment_elem = vertexboneassignment_elem->NextSiblingElement("vertexboneassignment"))
    {
        int BoneID = RequireIntAttribute(vertexboneassignment_elem, "boneindex");
        int VertexIndex = RequireIntAttribute(vertexboneassignment_elem, "vertexindex");
        float weight = RequireFloatAttribute(vertexboneassignment_elem, "weight");
 
        if (VertexIndex < 0 || static_cast<unsigned int>(VertexIndex) >= vertices.size())
            Error(FormatString("Vertex index in bone assignment (%d) is out of range", VertexIndex), vertexboneassignment_elem);
 
        // maybe not needed, see comment below
        const StdMeshBone* bone = nullptr;
        for (unsigned int i = 0; !bone && i < mesh.GetSkeleton().GetNumBones(); ++i)
            if (mesh.GetSkeleton().GetBone(i).ID == BoneID)
                bone = &mesh.GetSkeleton().GetBone(i);
 
        if (!bone) Error(FormatString("There is no such bone with ID %d", BoneID), vertexboneassignment_elem);
 
        // Find first bone assignment with a zero weight (i.e. is unused)
        StdSubMesh::Vertex& vertex = vertices[VertexIndex];
        // Check quickly if all weight slots are used
        if (vertex.bone_weight[StdMeshVertex::MaxBoneWeightCount - 1] != 0)
        {
            Error(FormatString("Vertex %d is influenced by more than %d bones", VertexIndex, static_cast<int>(StdMeshVertex::MaxBoneWeightCount)), vertexboneassignment_elem);
        }
        for (size_t weight_index = 0; weight_index < StdMeshVertex::MaxBoneWeightCount; ++weight_index)
        {
            if (vertex.bone_weight[weight_index] == 0)
            {
                vertex.bone_weight[weight_index] = weight;
                vertex.bone_index[weight_index] = bone->Index;
                break;
            }
        }
    }
 
    // Normalize vertex bone assignment weights (this is not guaranteed in the
    // Ogre file format).
    for (auto & vertex : vertices)
    {
        float sum = 0.0;
        for (float weight : vertex.bone_weight)
            sum += weight;
        if (sum != 0)
            for (float &weight : vertex.bone_weight)
                weight /= sum;
        else
            vertex.bone_weight[0] = 1.0f;
    }
}
 
StdMesh *StdMeshLoader::LoadMeshXml(const char* xml_data, size_t size, const StdMeshMatManager& manager, StdMeshSkeletonLoader& skel_loader, const char* filename)
{
    StdMeshXML xml(filename ? filename : "<unknown>", xml_data);
 
    std::unique_ptr<StdMesh> mesh(new StdMesh);
 
    TiXmlElement* mesh_elem = xml.RequireFirstChild(nullptr, "mesh");
 
    // Load shared geometry, if any
    TiXmlElement* sharedgeometry_elem = mesh_elem->FirstChildElement("sharedgeometry");
    if(sharedgeometry_elem != nullptr)
        xml.LoadGeometry(*mesh, mesh->SharedVertices, sharedgeometry_elem);
 
    TiXmlElement* submeshes_elem = xml.RequireFirstChild(mesh_elem, "submeshes");
 
    TiXmlElement* submesh_elem_base = xml.RequireFirstChild(submeshes_elem, "submesh");
    for (TiXmlElement* submesh_elem = submesh_elem_base; submesh_elem != nullptr; submesh_elem = submesh_elem->NextSiblingElement("submesh"))
    {
        mesh->SubMeshes.push_back(StdSubMesh());
        StdSubMesh& submesh = mesh->SubMeshes.back();
 
        const char* material = xml.RequireStrAttribute(submesh_elem, "material");
        submesh.Material = manager.GetMaterial(material);
        if (!submesh.Material)
            xml.Error(FormatString("There is no such material named '%s'", material), submesh_elem);
 
        const char* usesharedvertices = submesh_elem->Attribute("usesharedvertices");
        const std::vector<StdMesh::Vertex>* vertices;
        if(!usesharedvertices || strcmp(usesharedvertices, "true") != 0)
        {
            TiXmlElement* geometry_elem = xml.RequireFirstChild(submesh_elem, "geometry");
            xml.LoadGeometry(*mesh, submesh.Vertices, geometry_elem);
            vertices = &submesh.Vertices;
        }
        else
        {
            if(mesh->SharedVertices.empty())
                xml.Error(StdCopyStrBuf("Submesh specifies to use shared vertices but there is no shared geometry"), submesh_elem);
            vertices = &mesh->SharedVertices;
        }
 
        TiXmlElement* faces_elem = xml.RequireFirstChild(submesh_elem, "faces");
        int FaceCount = xml.RequireIntAttribute(faces_elem, "count");
        submesh.Faces.resize(FaceCount);
 
        unsigned int i = 0;
        for (TiXmlElement* face_elem = faces_elem->FirstChildElement("face"); face_elem != nullptr && i < submesh.Faces.size(); face_elem = face_elem->NextSiblingElement("face"), ++i)
        {
            int v[3];
 
            v[0] = xml.RequireIntAttribute(face_elem, "v1");
            v[1] = xml.RequireIntAttribute(face_elem, "v2");
            v[2] = xml.RequireIntAttribute(face_elem, "v3");
 
            for (unsigned int j = 0; j < 3; ++j)
            {
                if (v[j] < 0 || static_cast<unsigned int>(v[j]) >= vertices->size())
                    xml.Error(FormatString("Vertex index v%u (%d) is out of range", j+1, v[j]), face_elem);
                submesh.Faces[i].Vertices[j] = v[j];
            }
        }
    }
 
    // We allow bounding box to be empty if it's only due to Z direction since
    // this is what goes inside the screen in Clonk.
    if(mesh->BoundingBox.x1 == mesh->BoundingBox.x2 || mesh->BoundingBox.y1 == mesh->BoundingBox.y2)
        xml.Error(StdCopyStrBuf("Bounding box is empty"), mesh_elem);
 
    // Read skeleton, if any
    TiXmlElement* skeletonlink_elem = mesh_elem->FirstChildElement("skeletonlink");
    if (skeletonlink_elem)
    {
        const char* name = xml.RequireStrAttribute(skeletonlink_elem, "name");
        StdCopyStrBuf xml_filename(name); xml_filename.Append(".xml");
 
        StdCopyStrBuf skeleton_filename;
        StdMeshSkeletonLoader::MakeFullSkeletonPath(skeleton_filename, filename, xml_filename.getData());
 
        mesh->Skeleton = skel_loader.GetSkeletonByName(skeleton_filename);
        if (!mesh->Skeleton) xml.Error(FormatString("Failed to load '%s'", skeleton_filename.getData()), skeletonlink_elem);
 
        // Vertex<->Bone assignments for shared geometry
        if (sharedgeometry_elem)
        {
            TiXmlElement* boneassignments_elem = xml.RequireFirstChild(mesh_elem, "boneassignments");
            xml.LoadBoneAssignments(*mesh, mesh->SharedVertices, boneassignments_elem);
        }
 
        // Vertex<->Bone assignments for all vertices (need to go through SubMeshes again...)
        unsigned int submesh_index = 0;
        for (TiXmlElement* submesh_elem = submesh_elem_base; submesh_elem != nullptr; submesh_elem = submesh_elem->NextSiblingElement("submesh"), ++submesh_index)
        {
            StdSubMesh& submesh = mesh->SubMeshes[submesh_index];
            if (!submesh.Vertices.empty())
            {
                TiXmlElement* boneassignments_elem = xml.RequireFirstChild(submesh_elem, "boneassignments");
                xml.LoadBoneAssignments(*mesh, submesh.Vertices, boneassignments_elem);
            }
        }
    }
    else
    {
        // Mesh has no skeleton
        // Bone assignements do not make sense then, as the
        // actual bones are defined in the skeleton file.
        for (TiXmlElement* submesh_elem = submesh_elem_base; submesh_elem != nullptr; submesh_elem = submesh_elem->NextSiblingElement("submesh"))
        {
            TiXmlElement* boneassignments_elem = submesh_elem->FirstChildElement("boneassignments");
            if (boneassignments_elem)
                xml.Error(StdStrBuf("Mesh has bone assignments, but no skeleton"), boneassignments_elem);
        }
 
        TiXmlElement* boneassignments_elem = mesh_elem->FirstChildElement("boneassignments");
        if (boneassignments_elem)
            xml.Error(StdStrBuf("Mesh has bone assignments, but no skeleton"), boneassignments_elem);
    }
 
    return mesh.release();
}
 
void StdMeshSkeletonLoader::LoadSkeletonXml(const char* groupname, const char* filename, const char *sourcefile, size_t size)
{
    if (sourcefile == nullptr)
    {
        throw Ogre::InsufficientData(FormatString("Failed to load '%s/%s'", groupname, filename).getData());
    }
 
    std::shared_ptr<StdMeshLoader::StdMeshXML> skeleton(new StdMeshLoader::StdMeshXML(filename, sourcefile));
 
    TiXmlElement* skeleton_elem = skeleton->RequireFirstChild(nullptr, "skeleton");
    TiXmlElement* bones_elem = skeleton->RequireFirstChild(skeleton_elem, "bones");
 
    // Read bones. Don't insert into Master bone table yet, as the master bone
    // table is sorted hierarchically, and we will read the hierarchy only
    // afterwards.
    std::vector<StdMeshBone*> bones;
    for (TiXmlElement* bone_elem = bones_elem->FirstChildElement("bone"); bone_elem != nullptr; bone_elem = bone_elem->NextSiblingElement("bone"))
    {
        StdMeshBone* bone = new StdMeshBone;
        bones.push_back(bone);
 
        bone->ID = skeleton->RequireIntAttribute(bone_elem, "id");
        bone->Name = skeleton->RequireStrAttribute(bone_elem, "name");
        // TODO: Make sure ID and name are unique
 
        bone->Parent = nullptr;
        // Index of bone will be set when building Master Bone Table later
 
        TiXmlElement* position_elem = skeleton->RequireFirstChild(bone_elem, "position");
        TiXmlElement* rotation_elem = skeleton->RequireFirstChild(bone_elem, "rotation");
        TiXmlElement* axis_elem = skeleton->RequireFirstChild(rotation_elem, "axis");
 
        StdMeshVector d, r;
        d.x = skeleton->RequireFloatAttribute(position_elem, "x");
        d.y = skeleton->RequireFloatAttribute(position_elem, "y");
        d.z = skeleton->RequireFloatAttribute(position_elem, "z");
        float angle = skeleton->RequireFloatAttribute(rotation_elem, "angle");
        r.x = skeleton->RequireFloatAttribute(axis_elem, "x");
        r.y = skeleton->RequireFloatAttribute(axis_elem, "y");
        r.z = skeleton->RequireFloatAttribute(axis_elem, "z");
 
        bone->Transformation.scale = StdMeshVector::UnitScale();
        bone->Transformation.rotate = StdMeshQuaternion::AngleAxis(angle, r);
        bone->Transformation.translate = d;
 
        // We need this later for applying animations, and attaching meshes, therefore cache it here
        bone->InverseTransformation = StdMeshTransformation::Inverse(bone->Transformation);
    }
 
    // Bone hierarchy
    TiXmlElement* bonehierarchy_elem = skeleton->RequireFirstChild(skeleton_elem, "bonehierarchy");
    for (TiXmlElement* boneparent_elem = bonehierarchy_elem->FirstChildElement("boneparent"); boneparent_elem != nullptr; boneparent_elem = boneparent_elem->NextSiblingElement("boneparent"))
    {
        const char* child_name = skeleton->RequireStrAttribute(boneparent_elem, "bone");
        const char* parent_name = skeleton->RequireStrAttribute(boneparent_elem, "parent");
 
        // Lookup the two bones
        StdMeshBone* child = nullptr;
        StdMeshBone* parent = nullptr;
        for (unsigned int i = 0; i < bones.size() && (!child || !parent); ++i)
        {
            if (!child && bones[i]->Name == child_name)
                child = bones[i];
            if (!parent && bones[i]->Name == parent_name)
                parent = bones[i];
        }
 
        if (!child) skeleton->Error(FormatString("There is no such bone with name '%s'", child_name), boneparent_elem);
        if (!parent) skeleton->Error(FormatString("There is no such bone with name '%s'", parent_name), boneparent_elem);
 
        child->Parent = parent;
        parent->Children.push_back(child);
    }
 
    std::shared_ptr<StdMeshSkeleton> Skeleton(new StdMeshSkeleton);
 
    // Fill master bone table in hierarchical order:
    for (auto & bone : bones)
        if (bone->Parent == nullptr)
            Skeleton->AddMasterBone(bone);
 
    // Load Animations
    TiXmlElement* animations_elem = skeleton_elem->FirstChildElement("animations");
    if (animations_elem)
    {
        for (TiXmlElement* animation_elem = animations_elem->FirstChildElement("animation"); animation_elem != nullptr; animation_elem = animation_elem->NextSiblingElement("animation"))
        {
            StdCopyStrBuf name(skeleton->RequireStrAttribute(animation_elem, "name"));
            if (Skeleton->Animations.find(name) != Skeleton->Animations.end())
                skeleton->Error(FormatString("There is already an animation with name '%s'", name.getData()), animation_elem);
 
            StdMeshAnimation& animation = Skeleton->Animations.insert(std::make_pair(name, StdMeshAnimation())).first->second;
            animation.Name = name;
            animation.Length = skeleton->RequireFloatAttribute(animation_elem, "length");
            animation.Tracks.resize(Skeleton->GetNumBones());
            animation.OriginSkeleton = &(*Skeleton);
 
            TiXmlElement* tracks_elem = skeleton->RequireFirstChild(animation_elem, "tracks");
            for (TiXmlElement* track_elem = tracks_elem->FirstChildElement("track"); track_elem != nullptr; track_elem = track_elem->NextSiblingElement("track"))
            {
                const char* bone_name = skeleton->RequireStrAttribute(track_elem, "bone");
                StdMeshBone* bone = nullptr;
                for (unsigned int i = 0; !bone && i < Skeleton->GetNumBones(); ++i)
                    if (Skeleton->Bones[i]->Name == bone_name)
                        bone = Skeleton->Bones[i];
                if (!bone) skeleton->Error(FormatString("There is no such bone with name '%s'", bone_name), track_elem);
 
                if (animation.Tracks[bone->Index] != nullptr) skeleton->Error(FormatString("There is already a track for bone '%s' in animation '%s'", bone_name, animation.Name.getData()), track_elem);
 
                StdMeshTrack* track = new StdMeshTrack;
                animation.Tracks[bone->Index] = track;
 
                TiXmlElement* keyframes_elem = skeleton->RequireFirstChild(track_elem, "keyframes");
                for (TiXmlElement* keyframe_elem = keyframes_elem->FirstChildElement("keyframe"); keyframe_elem != nullptr; keyframe_elem = keyframe_elem->NextSiblingElement("keyframe"))
                {
                    float time = skeleton->RequireFloatAttribute(keyframe_elem, "time");
                    StdMeshKeyFrame& frame = track->Frames[time];
 
                    TiXmlElement* translate_elem = keyframe_elem->FirstChildElement("translate");
                    TiXmlElement* rotate_elem = keyframe_elem->FirstChildElement("rotate");
                    TiXmlElement* scale_elem = keyframe_elem->FirstChildElement("scale");
 
                    StdMeshVector d, s, r;
                    d.x = d.y = d.z = 0.0f;
                    s = StdMeshVector::UnitScale();
                    r.x = r.y = 0.0f; r.z = 1.0f;
                    float angle = 0.0f;
 
                    if (translate_elem)
                    {
                        d.x = skeleton->RequireFloatAttribute(translate_elem, "x");
                        d.y = skeleton->RequireFloatAttribute(translate_elem, "y");
                        d.z = skeleton->RequireFloatAttribute(translate_elem, "z");
                    }
 
                    if (rotate_elem)
                    {
                        TiXmlElement* axis_elem = skeleton->RequireFirstChild(rotate_elem, "axis");
                        angle = skeleton->RequireFloatAttribute(rotate_elem, "angle");
                        r.x = skeleton->RequireFloatAttribute(axis_elem, "x");
                        r.y = skeleton->RequireFloatAttribute(axis_elem, "y");
                        r.z = skeleton->RequireFloatAttribute(axis_elem, "z");
                    }
 
                    if (scale_elem)
                    {
                        s.x = skeleton->RequireFloatAttribute(scale_elem, "x");
                        s.y = skeleton->RequireFloatAttribute(scale_elem, "y");
                        s.z = skeleton->RequireFloatAttribute(scale_elem, "z");
                    }
 
                    frame.Transformation.scale = s;
                    frame.Transformation.rotate = StdMeshQuaternion::AngleAxis(angle, r);
                    frame.Transformation.translate = bone->InverseTransformation.rotate * (bone->InverseTransformation.scale * d);
                    frame.Transformation = OgreToClonk::TransformTransformation(frame.Transformation);
                }
            }
        }
    }
 
    // is there even any xml file that we load from?
    // it looks like this could never work: if the mesh has no skeleton, then the code below will fail because of a null pointer...
 
    // Apply parent transformation to each bone transformation. We need to
    // do this late since animation keyframe computation needs the bone
    // transformations, not bone+parent.
    for (unsigned int i = 0; i < Skeleton->GetNumBones(); ++i)
    {
        // Apply parent transformation
        if (Skeleton->Bones[i]->Parent)
            Skeleton->Bones[i]->Transformation = Skeleton->Bones[i]->Parent->Transformation * OgreToClonk::TransformTransformation(Skeleton->Bones[i]->Transformation);
        else
            Skeleton->Bones[i]->Transformation = OgreToClonk::TransformTransformation(Skeleton->Bones[i]->Transformation);
 
        // Update inverse
        Skeleton->Bones[i]->InverseTransformation = StdMeshTransformation::Inverse(Skeleton->Bones[i]->Transformation);
    }
 
    StoreSkeleton(groupname, filename, Skeleton);
}