Confusion over transforms

Development Programming & Scripting C++
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1

I was getting some odd results with what I was expecting from transforms so I setup a test. There are several problems here:

  • When I move the parent bone -100 in x, the local location of the child bone is -100 - it should be 0. In world space it should be -100.
  • ChildTransform and ChildTransform2 should be the same.

Here’s a pastebin with cleaner formatting:

FName ParentBoneName = TEXT("Root");
FName ChildBoneName = TEXT("Turret");

Turret->Mesh->SetBoneLocationByName(ParentBoneName, FVector(-100, 0, 0), EBoneSpaces::WorldSpace);
TestEqual(TEXT("Parent Transform"), Turret->Mesh->GetBoneTransformByName(ParentBoneName, EBoneSpaces::WorldSpace).GetLocation(), FVector(-100, 0, 0));
TestEqual(TEXT("Child Location"), Turret->Mesh->GetBoneLocationByName(ChildBoneName, EBoneSpaces::ComponentSpace), FVector(0, 0, 20));
TestEqual(TEXT("Child Location"), Turret->Mesh->GetBoneLocationByName(ChildBoneName, EBoneSpaces::WorldSpace), FVector(-100, 0, 20));

Turret->Mesh->SetBoneRotationByName(ParentBoneName, FRotator(45, 0, 0), EBoneSpaces::ComponentSpace);
TestEqual(TEXT("Parent Transform"), Turret->Mesh->GetBoneTransformByName(ParentBoneName, EBoneSpaces::WorldSpace).GetRotation().Rotator(), FRotator(45, 0, 0));
TestEqual(TEXT("Child Rotation"), Turret->Mesh->GetBoneRotationByName(ChildBoneName, EBoneSpaces::ComponentSpace), FRotator(0, 0, 0));
TestEqual(TEXT("Child Rotation"), Turret->Mesh->GetBoneRotationByName(ChildBoneName, EBoneSpaces::WorldSpace), FRotator(45, 0, 0));

FTransform ChildTransform = Turret->Mesh->GetBoneTransformByName(ChildBoneName, EBoneSpaces::WorldSpace);
FTransform LocalChildTransform = ChildTransform.GetRelativeTransform(Turret->Mesh->GetBoneTransformByName(ParentBoneName, EBoneSpaces::WorldSpace));
FTransform ChildTransform2 = LocalChildTransform.GetRelativeTransformReverse(Turret->Mesh->GetBoneTransformByName(ParentBoneName, EBoneSpaces::WorldSpace));
TestEqual(TEXT("Transform Location"), ChildTransform.GetLocation(), ChildTransform2.GetLocation());
TestEqual(TEXT("Transform Rotation"), ChildTransform.GetRotation(), ChildTransform2.GetRotation());
2

Same here. For a whole animation I am doing by hand by applying rotation and translation to the bones of a PoseableMesh in C++, both the EBoneSpaces::ComponentSpace and EBoneSpaces::WorldSpace rotation and translation are the same when printing it. Shouldn’t there be a difference?