Transform multiple bones same animation blueprint

Development Character & Animation
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1

Hi Guys,

I’m trying to transform multiple bones in the same custom animation blueprint. I’m using the Transform (Modify) Bone code present in the source of the engine

    void FMyClassAnimNode::EvaluateBoneTransforms(USkeletalMeshComponent* SkelComp, FCSPose<FCompactPose>& MeshBases, TArray<FBoneTransform>& OutBoneTransforms)
    {
        check(OutBoneTransforms.Num() == 0);
        
        const FBoneContainer& BoneContainer = MeshBases.GetPose().GetBoneContainer();
        
        FCompactPoseBoneIndex CompactPoseBoneToModify = BoneToModify.GetCompactPoseIndex(BoneContainer);
        FTransform NewBoneTM = MeshBases.GetComponentSpaceTransform(CompactPoseBoneToModify);
        
        FAnimationRuntime::ConvertCSTransformToBoneSpace(SkelComp, MeshBases, NewBoneTM, CompactPoseBoneToModify, RotationSpace);
        
        FRotator Rotation = FRotator();
        Rotation.Pitch = 1.0f*counter;
        
        const FQuat BoneQuat(Rotation);
        NewBoneTM.SetRotation(BoneQuat * NewBoneTM.GetRotation());
        
        FAnimationRuntime::ConvertBoneSpaceTransformToCS(SkelComp, MeshBases, NewBoneTM, CompactPoseBoneToModify, RotationSpace);

         counter++;
OutBoneTransforms.Add(FBoneTransform(BoneToModify.GetCompactPoseIndex(BoneContainer), NewBoneTM));
    }

To do the additional transformation I just use BoneToModify2 that contains the reference to the another bone and replicate this code after the OutBoneTransforms.Add. But the moment I update the animation blueprint for this code it just breaks unreal… Does anyone know why? And how to fix this?

Thanks!

2

This is possible by changing a little how you apply your transforms inside EvaluateSkeletalControl_AnyThread

In essence you change the line at the end from

OutBoneTransforms.Add(FBoneTransform(compactbone, NewBoneTM));

to:

TempTransforms.Add(FBoneTransform(compactbone, NewBoneTM));
Output.Pose.LocalBlendCSBoneTransforms(TempTransforms, BlendWeight);
TempTransforms.Reset();

Which applies each transform before processing the next transform if it’s placed inside a loop going over each of your bones.

1 Like
3

This has really helped, thank you! Any downsides to this approach that you are aware of?