Problem with bone weight

Anonymous — Thu, 09 Jun 2016 16:56:39 GMT

Hi,

I am trying to export a character using the FBX-SDK. I can export the mesh and the bones correctly, but adding weights to the mesh is not working correctly. The file without weights looks like this (Left: Blender, Right: FbxReview):

The file with weights looks like this:

The weights of the vertices are actually correct (if I move a bone the corresponding part of the mesh moves), but the position is off. I suspect it has something to do with SetTransformMatrix or SetTransformLinkMatrix? I also had some problems with the rotation order (had to set it to ZXY) and inherit types (had to set it to RSrs) before, but I don't think that is relevant here since the matrices are set directly (but maybe I am wrong?).

My code for adding the weights looks like this:

if (obj->hasWeights()) {
	FbxAMatrix meshMatrix = meshNode->EvaluateGlobalTransform();
	FbxSkin* skin = obj->addSkin(manager);
	FbxPose* bindPose = FbxPose::Create(manager, "BindPose");
	bindPose->SetIsBindPose(true);
	std::map<Bone*, std::list<struct VertexWeight>> weights = obj->getVertexWeights();
	for (std::pair<Bone*, std::list<struct VertexWeight>> pair : weights) {
		Bone* curBone = pair.first;
		FbxCluster* cluster = curBone->createCluster(manager);
		for (VertexWeight weight : pair.second) {
			cluster->AddControlPointIndex(weight.vertexIndex, weight.weight);
		}
		FbxNode* boneNode = curBone->getNode();
		FbxAMatrix boneMatrix = boneNode->EvaluateGlobalTransform();
		cluster->SetTransformMatrix(meshMatrix);
		cluster->SetTransformLinkMatrix(boneMatrix);
		skin->AddCluster(cluster);
		FbxNode* curNode = boneNode;
		while (curNode!=nullptr) {
			if(bindPose->Find(curNode)==-1) {
				bindPose->Add(curNode, curNode->EvaluateGlobalTransform());
			}
			curNode = curNode->GetParent();
		}

	}
	
	scene->AddPose(bindPose);
}

FbxSkin * UObject::addSkin(FbxManager * manager)
{
	this->skin = FbxSkin::Create(manager, this->name.c_str());
	((FbxGeometry*)this->node->GetNodeAttribute())->AddDeformer(this->skin);
	return this->skin;
}

FbxCluster * Bone::createCluster(FbxManager * manager)
{
	this->cluster = FbxCluster::Create(manager, this->name.c_str());
	this->cluster->SetLink(this->node);
	this->cluster->SetLinkMode(FbxCluster::ELinkMode::eNormalize);
	return this->cluster;
}

Any ideas or hints are much appreciated.

Thanks

Re: Problem with bone weight

Anonymous — Mon, 13 Jun 2016 07:39:52 GMT

Turns out that the SDK does not always respect the specified rotation order ... I changed my application to use quaternions and converted the quaternions in the SDK (as described HERE), which seems like the most secure option. The code for the bone weights in my original post did not change.

topic Re: Problem with bone weight in FBX Forum

Problem with bone weight

Re: Problem with bone weight