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Quaid Tseng

Unity Exporting MAYA skinning mesh and boneoffset matrix problems

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I've gone though almost all the tutors on web like RobTheBloke and florian.loitsch's gpExport. And I already sucessfully export a static mesh and render it in my engine. But I still failed to render an exported skinned mesh. I had the exp about render a .X file animation so I know the formula for skinning: vertex pos = vertexbindpos * boneoffset * jointworldtranform * bindweight I tried to extract the boneoffset like the following (a mix of RobTheBloke and gpExport and Chad Vernon's cvxport) but I got a distorted result and hope someone can tell me where the problem is.
BoneIT it = g_Bones.begin();
for( ; it != g_Bones.end(); ++it ){
	MFnTransform fnX(bone.path);

	//---------------------Get BindPoseMatrix using the function in gpExport---------------------
	MFnIkJoint joint(bone.path.node());
	MMatrix bindPoseMatrix = getBindPoseMatrix(joint);
	bindPoseMatrix = bindPoseMatrix.inverse();

	//---------------------Get Joint's Transform matrix---------------------
	MMatrix mat = fnX.transformation().asMatrix();
		MStatus s = bone.path.pop();
		if(s == MS::kSuccess){
			MFnTransform fnXP(bone.path.node());
			mat *= fnXP.transformationMatrix();
		else break;
	mat = mat.inverse();
	MMatrix boneoffset = bindPoseMatrix * mat;

But obviously this is not boneoffset, what I saw were all pure rotations, its weird that there's no translation, and the rotations are incorrect either. I just wonder that the joint's transform matrix, Using while(true) to accumulate the transform of all its ancestors. Actually I modified it(Chad's cvxporter in python) to C++, but I'm not sure if I've done it in a correct way. The bindpose matrix I used that from gpExport http://florian.loitsch.com/gpExport/index-4.html#Extraction It's like
MMatrix getBindPoseMatrix(MFnIkJoint joint)
    // get bindPose-plug on joint
    MPlug tempBindPosePlug = joint.findPlug("bindPose");

    MPlugArray mapConnections;
    tempBindPosePlug.connectedTo(mapConnections, false, true);

    if (mapConnections.length() != 1)
        //cout << "returning currentMatrix" << endl;
        // certainly not the most correct way of dealing with the problem...
        return joint.transformation().asMatrix();

    // find the other end. actually we shouldn't call it "bindPosePlug",
    // but worldTransformPlug (as that's where it enters).

    // theoretically someone could bind the bindPose to other nodes,
    // than the bindPose-node. in this case there's a problem.
    MPlug bindPosePlug = mapConnections[0];

    // this node should be a "dagPose"-node (in case you want to look it
    // up in the help)
    MFnDependencyNode bindPoseNode(bindPosePlug.node());

    // and as such, has the "xformMatrix"-attribute.
    MObject xformMatrixAttribute = bindPoseNode.attribute("xformMatrix");

    MPlug localTransformPlug(bindPosePlug.node(), xformMatrixAttribute);
    // xformMatrix is an array. to get our localmatrix we need to select
    // the same index, as our bindPosePlug (logicalIndex()).
    localTransformPlug.selectAncestorLogicalIndex(bindPosePlug.logicalIndex(), xformMatrixAttribute);

    MObject localMatrixObject;
    // extract the matrix out of the object.
    return MFnMatrixData(localMatrixObject).matrix();

BTW, I'm confused about the transforms in MAYA, http://www.gamedev.net/community/forums/topic.asp?topic_id=517946 And I've tried Rotation = RO * R * JO That's Rotation = Rotate Orient * Rotation * Joint Orient
BoneIT it = g_Bones.begin();
for( ; it != g_Bones.end(); ++it ){
	MMatrix test;
	MQuaternion JO(0,0,0,1);
	MQuaternion RO(0,0,0,1);
	MQuaternion Rcomb;
	MMatrix RcombMat;

	// Rotation

	if( fnX.object().hasFn(MFn::kJoint) )
		// Joint Orientation
		MFnIkJoint fnJ(fnX.object());
	// Rotate Orientation
	RO = fnX.rotateOrientation(MSpace::kObject);

	// Test Rotate = [RO] * [R] * [JO]
	RcombMat = RO.asMatrix() * R.asMatrix();
	RcombMat = RcombMat * JO.asMatrix();
	Rcomb = RcombMat;

	MVector trans = fnX.translation(MSpace::kTransform);
	// Test Transform = [S] * [RO] * [R] * [JO] * [IS] * [T]
	MMatrix translationMat; translationMat.setToIdentity();
	translationMat(3,0) = trans.x;
	translationMat(3,1) = trans.y;
	translationMat(3,2) = trans.z;

	test = RcombMat * translationMat;

I think this should be the jointworldtranform that transform the origin to joint position, but it's not, I was wrong. Really hope someone can help me. I've spent a lot time on it but still can't work out. Any idea is appreciated. [Edited by - Quaid Tseng on March 4, 2010 7:44:22 PM]

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