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/** @file  SkeletonMeshBuilder.cpp
 *  @brief Implementation of a little class to construct a dummy mesh for a skeleton
 */

#include <assimp/scene.h>
#include "SkeletonMeshBuilder.h"

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
// The constructor processes the given scene and adds a mesh there.
SkeletonMeshBuilder::SkeletonMeshBuilder( aiScene* pScene, aiNode* root, bool bKnobsOnly)
{
    // nothing to do if there's mesh data already present at the scene
    if( pScene->mNumMeshes > 0 || pScene->mRootNode == NULL)
        return;

    if (!root)
        root = pScene->mRootNode;

    mKnobsOnly = bKnobsOnly;

    // build some faces around each node
    CreateGeometry( root );

    // create a mesh to hold all the generated faces
    pScene->mNumMeshes = 1;
    pScene->mMeshes = new aiMesh*[1];
    pScene->mMeshes[0] = CreateMesh();
    // and install it at the root node
    root->mNumMeshes = 1;
    root->mMeshes = new unsigned int[1];
    root->mMeshes[0] = 0;

    // create a dummy material for the mesh
    if(pScene->mNumMaterials==0){
		pScene->mNumMaterials = 1;
		pScene->mMaterials = new aiMaterial*[1];
		pScene->mMaterials[0] = CreateMaterial();
    }
}

// ------------------------------------------------------------------------------------------------
// Recursively builds a simple mesh representation for the given node
void SkeletonMeshBuilder::CreateGeometry( const aiNode* pNode)
{
    // add a joint entry for the node.
    const unsigned int vertexStartIndex = mVertices.size();

    // now build the geometry.
    if( pNode->mNumChildren > 0 && !mKnobsOnly)
    {
        // If the node has children, we build little pointers to each of them
        for( unsigned int a = 0; a < pNode->mNumChildren; a++)
        {
            // find a suitable coordinate system
            const aiMatrix4x4& childTransform = pNode->mChildren[a]->mTransformation;
            aiVector3D childpos( childTransform.a4, childTransform.b4, childTransform.c4);
            float distanceToChild = childpos.Length();
            if( distanceToChild < 0.0001f)
                continue;
            aiVector3D up = aiVector3D( childpos).Normalize();

            aiVector3D orth( 1.0f, 0.0f, 0.0f);
            if( std::fabs( orth * up) > 0.99f)
                orth.Set( 0.0f, 1.0f, 0.0f);

            aiVector3D front = (up ^ orth).Normalize();
            aiVector3D side = (front ^ up).Normalize();

            unsigned int localVertexStart = mVertices.size();
            mVertices.push_back( -front * distanceToChild * 0.1f);
            mVertices.push_back( childpos);
            mVertices.push_back( -side * distanceToChild * 0.1f);
            mVertices.push_back( -side * distanceToChild * 0.1f);
            mVertices.push_back( childpos);
            mVertices.push_back( front * distanceToChild * 0.1f);
            mVertices.push_back( front * distanceToChild * 0.1f);
            mVertices.push_back( childpos);
            mVertices.push_back( side * distanceToChild * 0.1f);
            mVertices.push_back( side * distanceToChild * 0.1f);
            mVertices.push_back( childpos);
            mVertices.push_back( -front * distanceToChild * 0.1f);

            mFaces.push_back( Face( localVertexStart + 0, localVertexStart + 1, localVertexStart + 2));
            mFaces.push_back( Face( localVertexStart + 3, localVertexStart + 4, localVertexStart + 5));
            mFaces.push_back( Face( localVertexStart + 6, localVertexStart + 7, localVertexStart + 8));
            mFaces.push_back( Face( localVertexStart + 9, localVertexStart + 10, localVertexStart + 11));
        }
    }
    else
    {
        // if the node has no children, it's an end node. Put a little knob there instead
        aiVector3D ownpos( pNode->mTransformation.a4, pNode->mTransformation.b4, pNode->mTransformation.c4);
        float sizeEstimate = ownpos.Length() * 0.18f;

        mVertices.push_back( aiVector3D( -sizeEstimate, 0.0f, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, sizeEstimate, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, 0.0f, -sizeEstimate));
        mVertices.push_back( aiVector3D( 0.0f, sizeEstimate, 0.0f));
        mVertices.push_back( aiVector3D( sizeEstimate, 0.0f, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, 0.0f, -sizeEstimate));
        mVertices.push_back( aiVector3D( sizeEstimate, 0.0f, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, -sizeEstimate, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, 0.0f, -sizeEstimate));
        mVertices.push_back( aiVector3D( 0.0f, -sizeEstimate, 0.0f));
        mVertices.push_back( aiVector3D( -sizeEstimate, 0.0f, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, 0.0f, -sizeEstimate));

        mVertices.push_back( aiVector3D( -sizeEstimate, 0.0f, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, 0.0f, sizeEstimate));
        mVertices.push_back( aiVector3D( 0.0f, sizeEstimate, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, sizeEstimate, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, 0.0f, sizeEstimate));
        mVertices.push_back( aiVector3D( sizeEstimate, 0.0f, 0.0f));
        mVertices.push_back( aiVector3D( sizeEstimate, 0.0f, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, 0.0f, sizeEstimate));
        mVertices.push_back( aiVector3D( 0.0f, -sizeEstimate, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, -sizeEstimate, 0.0f));
        mVertices.push_back( aiVector3D( 0.0f, 0.0f, sizeEstimate));
        mVertices.push_back( aiVector3D( -sizeEstimate, 0.0f, 0.0f));

        mFaces.push_back( Face( vertexStartIndex + 0, vertexStartIndex + 1, vertexStartIndex + 2));
        mFaces.push_back( Face( vertexStartIndex + 3, vertexStartIndex + 4, vertexStartIndex + 5));
        mFaces.push_back( Face( vertexStartIndex + 6, vertexStartIndex + 7, vertexStartIndex + 8));
        mFaces.push_back( Face( vertexStartIndex + 9, vertexStartIndex + 10, vertexStartIndex + 11));
        mFaces.push_back( Face( vertexStartIndex + 12, vertexStartIndex + 13, vertexStartIndex + 14));
        mFaces.push_back( Face( vertexStartIndex + 15, vertexStartIndex + 16, vertexStartIndex + 17));
        mFaces.push_back( Face( vertexStartIndex + 18, vertexStartIndex + 19, vertexStartIndex + 20));
        mFaces.push_back( Face( vertexStartIndex + 21, vertexStartIndex + 22, vertexStartIndex + 23));
    }

    unsigned int numVertices = mVertices.size() - vertexStartIndex;
    if( numVertices > 0)
    {
        // create a bone affecting all the newly created vertices
        aiBone* bone = new aiBone;
        mBones.push_back( bone);
        bone->mName = pNode->mName;

        // calculate the bone offset matrix by concatenating the inverse transformations of all parents
        bone->mOffsetMatrix = aiMatrix4x4( pNode->mTransformation).Inverse();
        for( aiNode* parent = pNode->mParent; parent != NULL; parent = parent->mParent)
            bone->mOffsetMatrix = aiMatrix4x4( parent->mTransformation).Inverse() * bone->mOffsetMatrix;

        // add all the vertices to the bone's influences
        bone->mNumWeights = numVertices;
        bone->mWeights = new aiVertexWeight[numVertices];
        for( unsigned int a = 0; a < numVertices; a++)
            bone->mWeights[a] = aiVertexWeight( vertexStartIndex + a, 1.0f);

        // HACK: (thom) transform all vertices to the bone's local space. Should be done before adding
        // them to the array, but I'm tired now and I'm annoyed.
        aiMatrix4x4 boneToMeshTransform = aiMatrix4x4( bone->mOffsetMatrix).Inverse();
        for( unsigned int a = vertexStartIndex; a < mVertices.size(); a++)
            mVertices[a] = boneToMeshTransform * mVertices[a];
    }

    // and finally recurse into the children list
    for( unsigned int a = 0; a < pNode->mNumChildren; a++)
        CreateGeometry( pNode->mChildren[a]);
}

// ------------------------------------------------------------------------------------------------
// Creates the mesh from the internally accumulated stuff and returns it.
aiMesh* SkeletonMeshBuilder::CreateMesh()
{
    aiMesh* mesh = new aiMesh();

    // add points
    mesh->mNumVertices = mVertices.size();
    mesh->mVertices = new aiVector3D[mesh->mNumVertices];
    std::copy( mVertices.begin(), mVertices.end(), mesh->mVertices);

    mesh->mNormals = new aiVector3D[mesh->mNumVertices];

    // add faces
    mesh->mNumFaces = mFaces.size();
    mesh->mFaces = new aiFace[mesh->mNumFaces];
    for( unsigned int a = 0; a < mesh->mNumFaces; a++)
    {
        const Face& inface = mFaces[a];
        aiFace& outface = mesh->mFaces[a];
        outface.mNumIndices = 3;
        outface.mIndices = new unsigned int[3];
        outface.mIndices[0] = inface.mIndices[0];
        outface.mIndices[1] = inface.mIndices[1];
        outface.mIndices[2] = inface.mIndices[2];

        // Compute per-face normals ... we don't want the bones to be smoothed ... they're built to visualize
        // the skeleton, so it's good if there's a visual difference to the rest of the geometry
        aiVector3D nor = ((mVertices[inface.mIndices[2]] - mVertices[inface.mIndices[0]]) ^
            (mVertices[inface.mIndices[1]] - mVertices[inface.mIndices[0]]));

        if (nor.Length() < 1e-5f) /* ensure that FindInvalidData won't remove us ...*/
            nor = aiVector3D(1.f,0.f,0.f);

        for (unsigned int n = 0; n < 3; ++n)
            mesh->mNormals[inface.mIndices[n]] = nor;
    }

    // add the bones
    mesh->mNumBones = mBones.size();
    mesh->mBones = new aiBone*[mesh->mNumBones];
    std::copy( mBones.begin(), mBones.end(), mesh->mBones);

    // default
    mesh->mMaterialIndex = 0;

    return mesh;
}

// ------------------------------------------------------------------------------------------------
// Creates a dummy material and returns it.
aiMaterial* SkeletonMeshBuilder::CreateMaterial()
{
    aiMaterial* matHelper = new aiMaterial;

    // Name
    aiString matName( std::string( "SkeletonMaterial"));
    matHelper->AddProperty( &matName, AI_MATKEY_NAME);

    // Prevent backface culling
    const int no_cull = 1;
    matHelper->AddProperty(&no_cull,1,AI_MATKEY_TWOSIDED);

    return matHelper;
}
