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Question about bone transformations

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I'm implementing skeletal animations with Assimp for DX10 following this tutorial :http://ogldev.atspace.co.uk/www/tutorial38/tutorial38.html


For now, I can display the skinned mesh in global pose, filling the matrix palette with identities.


I don't understand the bone transformation explained in this tutorial, that is:


I think it should be :


1) offsetMatrix : to get from model space to bone space

2) scale*rotation*translation : transformation in bone space, get by interpoling animation keys,

3) inverseOffsetMatrix : to get back in model space.


Which one do you think is correct, please?





I tried both, and get incorrect results (abstract art instead of a ... duck sad.png )


Animation keys interpolation seems to work, but I wrongly compute the bone transformations apparently.

I suppose I don't understand correctly the aim of the offset matrix ... 


[EDITED2] fixed !


in fact the transformation for a node is :


and is for a bone :



In this tutorial it has been said :



If the node does not correspond to a bone then that is its final transformation. If it does we overwrite it with a matrix that we generate.


Actually it's not totally true, if an animation channel is associated to a node, we must also overrite the transform with animated one, even if it is not associated to a bone.

(Anyway, it would be odd that some animations channels would be defined for nothing ....)

Edited by Tournicoti

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I'm implementing the same skeletal animations with Assimp for DX11 but my is result is bad...

And i need some help...


Here is my ReadNodeHeirarchy:



void Mesh::ReadNodeHeirarchy(float AnimationTime, const aiNode* pNode, XMMATRIX ParentTransform)

    String NodeName(pNode->mName.data);
    const aiAnimation* pAnimation = m_pScene->mAnimations[0];
aiMatrix4x4 mat = pNode->mTransformation;
XMMATRIX NodeTransformation = TOXMMATRIX(mat);
    const aiNodeAnim* pNodeAnim = FindNodeAnim(pAnimation, NodeName);
    if (pNodeAnim) {
        // Interpolate scaling and generate scaling transformation matrix
        aiVector3D Scaling;
        CalcInterpolatedScaling(Scaling, AnimationTime, pNodeAnim);
        XMMATRIX ScalingM =XMMatrixScaling(Scaling.x, Scaling.y, Scaling.z);
        // Interpolate rotation and generate rotation transformation matrix
        aiQuaternion RotationQ;
        CalcInterpolatedRotation(RotationQ, AnimationTime, pNodeAnim);        
XMVECTOR axis = XMVectorSet(RotationQ.x,RotationQ.y,RotationQ.z,1);
XMMATRIX RotationM = XMMatrixRotationQuaternion(XMQuaternionRotationAxis(axis,RotationQ.w));
//RotationM = XMMatrixTranspose(RotationM);
        // Interpolate translation and generate translation transformation matrix
        aiVector3D Translation;
        CalcInterpolatedPosition(Translation, AnimationTime, pNodeAnim);
XMMATRIX TranslationM = XMMatrixTranslation(Translation.x, Translation.y, Translation.z);
        // Combine the above transformations
        NodeTransformation = ScalingM *  RotationM * TranslationM ;
XMMATRIX nodeTrans =  NodeTransformation * ParentTransform;
    if (m_BoneMapping.find(NodeName) != m_BoneMapping.end()) {
        unsigned int BoneIndex = m_BoneMapping[NodeName];
        m_BoneInfo[BoneIndex].FinalTransformation =  m_BoneInfo[BoneIndex].BoneOffset * nodeTrans * m_GlobalInverseTransform ;
// m_GlobalInverseTransform *  *  GlobalTransformation      ;
    for (unsigned int i = 0 ; i < pNode->mNumChildren ; i++) {
ReadNodeHeirarchy(AnimationTime, pNode->mChildren, nodeTrans);
Can you help me ?

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I've implemented skeletal animations in two phases : GPU side and CPU side.


1)I coded the shaders that do skinning, and checked them via offset matrices set to identity, to check if I display in this case the bind pose correctly.


2)Then I coded the animation controller, I had some difficulties at the begining but finally I get it work with the transformations I give for bones or for nodes in the first post.


Did you check the first point ? Do you get the bind pose with identity offset matrices ?

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