Hi all,
i’m working on game from some times, and i switched to C++ because i need specifics customs functionnality.
But thoses days i have a problem with modify an array of bones from my custom Anim Graph, let me explain:
I want modify rotation many spine bones (an array of bones), thoses bones wil lcopy with RInterpTo the **Effector **bone (to do dynamic dragon snake tail interpolation).
Like i see in source code for Transform Modify and Spline IK, the update it’s writing in
EvaluateSkeletalControl_AnyThread
The rotation work perfectly today, but the true problem it’s about update **Joint **position from parent bone of each bone iteration.
As i update an array of bones with the **OutBoneTransforms **FBoneTransform array, i think the component space don’t enought update the new bone transformation as long as we are in the **EvaluateSkeletalControl_AnyThread **function. So we need to recalculate new Joint bone from parent bone.
I’m insipired of **SplineIk **and **TwoBoneIk **to stuff it, but, there are things that escapes me (i have some many bugs with several try).
Usually I find the solution shortly with Google Search and Documentation, but i don’t find any solution in Forums and some web sites yet. 
**Reference of TwoBoneIK.cpp who try to updtae joint post of LowerClimb : **
I saturate on these calculations, that’s why I post here to have your lights / tips, can you help me please ? ^^
Sorry for this long text to read !
It’s the update transform part code :
// Effect it's the head bone in this exemple
FCompactPoseBoneIndex CompactEffectorPoseBoneToModify = Effector.GetCompactPoseIndex(BoneContainer);
// -- used for read only
const FTransform EffectorBoneTransform = Output.Pose.GetComponentSpaceTransform(CompactEffectorPoseBoneToModify);
// Last bone transform (the parent of current bone in for each)
FTransform InitialLastBoneTransform = EffectorBoneTransform;
FTransform LastBoneTransform = EffectorBoneTransform;
// For each child bone stored in my custom struct
for(MyCachedBone& CurrentCachdBone : MyCachedBoneList)
{
// Get current compact bone to modify
FCompactPoseBoneIndex CurrentCompactPoseBoneToModify = CurrentCachdBone.Bone.GetCompactPoseIndex(BoneContainer);
// -- used for read only
const FTransform CurrentBoneTransform = Output.Pose.GetComponentSpaceTransform(CurrentCompactPoseBoneToModify);
// -- used for modification
FTransform NewBoneTM = CurrentBoneTransform;
FTransform ComponentTransform = Output.AnimInstanceProxy->GetComponentTransform();
// =================================================
// -- ROTATION PART
// =================================================
// Convert to Bone Space.
FAnimationRuntime::ConvertCSTransformToBoneSpace(ComponentTransform, Output.Pose, NewBoneTM, CurrentCompactPoseBoneToModify, RotationSpace);
// -- Update Rotation Transform
const FQuat BoneQuat(NewRotation);
NewBoneTM.SetRotation(BoneQuat);
// Convert back to Component Space.
FAnimationRuntime::ConvertBoneSpaceTransformToCS(ComponentTransform, Output.Pose, NewBoneTM, CurrentCompactPoseBoneToModify, RotationSpace);
// =================================================
// -- LOCATION PART
// =================================================
// Convert to Bone Space.
FAnimationRuntime::ConvertCSTransformToBoneSpace(ComponentTransform, Output.Pose, NewBoneTM, CurrentCompactPoseBoneToModify, TranslationSpace);
// -- Update Translation Transform
FVector FinalJoinPos = LastBoneTransform.GetTranslation();
// Calcul length of joint
float BoneLength = (CurrentBoneTransform.GetTranslation() - InitialLastBoneTransform.GetTranslation()).Size();
// -- TODO
// will modify FinalJoinPos from some formula etc...
// ... Some stuff ...
// -- Apply final translation
NewBoneTM.SetTranslation(FinalJoinPos);
// Convert back to Component Space.
FAnimationRuntime::ConvertBoneSpaceTransformToCS(ComponentTransform, Output.Pose, NewBoneTM, CurrentCompactPoseBoneToModify, TranslationSpace);
// =================================================
// -- Apply transform and update next var
// =================================================
// Apply nexw transform
OutBoneTransforms.Add( FBoneTransform(BoneToModify.GetCompactPoseIndex(BoneContainer), NewBoneTM) );
// Finally update last transform
LastBoneTransform = NewBoneTM;
// And update last initial bone transform for next child
InitialLastBoneTransform = CurrentBoneTransform;
}
i would love to have your help,
Best regards 
