[Transform] The right way to set global rotation and position

Hi,

I have some code that output world positions and rotations. I'm working int a pure ECS context (with parenting transforms), so I'm at the last step and I see that LocalToWorld matrix can't be set because it's overwritten by TransformSystem at each update (also, I was fooled into thinking that Position and Rotation are world which is incorrect when there is a parent and it's very confusing).

So I have access to :
- Current localToWorld matrix
- New localToWorld matrix
- Parent localToWorld matrix

My solution is this :

Code (CSharp):

1. float4x4 newLocalMatrix = math.mul(math.inverse(parentMatrix), newWorldMatrix);

This code only works if there is no holes in the hierarchy I'm changing, for example if I have this :
A -> B - > C - >D
If I update only A, B and D the math would be wrong because I would not have updated C matrices.

Is there a plan to handle world positioning ?
Should we call the Update of TransformSystem manually when we need everything to be recalculated ?

Thanks!

 

As I understand it you want something like Transform.SetParent keeping the current world position.

Having a 'KeepWorldPosition' in the attach event component would be great.

 

Not really, I'm moving Entities based on world positions but these entities have parents / children. For now we have Position and Rotation, which are local if there is a parent, what I want is a SetWorldPosition / Rotation that would be more robust than my solution.

 

Why would you want to attach something if the transform should be independent?

 

My use case is an IK algorithm working with world positions / rotations, so I'm working on rigs which have transform hierarchies. Some bones could be skipped. So for example I move the wrist of an arm, the hand should follow because it's a child of the wrist.

 

Hmm, okay, makes sense.
I would probably update the hierrachy manually using a list of Bones sorted breadth first, as the problem is limited to specific subhierarchies.

 

Or, wait... I think you only have to remove Position/Rotation/Scale from the ones you control for yourself, then LocalToWorld shouldn't be touched by TransformSystem and the children still having these components still move correctly... I think.

 

That's a nice idea but doesn't the TransformSystem needs the parents to have Positions/Rotations components ?
I will need to think a lot to see if nothing breaks with this idea and I feel like it could give a little performance boost.
Thanks, that's a good alternative if it works but I still think that a SetWorldPosition would be useful.