Hello! I have some doubt regarding point constraint
So I have a joint A, I do a point contraint to another joint B
Now B should only translate from A but if I group B and rotate it, joint B starts translating around A
I have never seen this funcnality talked or written anywhere.. wondering what happening.
B should only able to rotate at its own pivot right since tranlation is constrained?
i have recorded a video showcasing my confusion
you added a constraint with an offset, that limits the offset to a certain length away from your driver, no mater how you move or change the parent this limits is always taken into account no matter wich orientation or postion you give the parent, if you added a parent constraint with offset the object would be locked into place even if you changed the parents rotation or translation
at the same time if you do a parentConstraint with offset and only use the translate connection (not the rotation connection) you will lock the object into place based on the offset of the driver, it will take the drivers rotation into account to drive this offset. if you rotate the parent, the driven object will rotate in place
It being rotated makes sense (since not constrained) but that group affecting its translation seems bit strange , and hard to understand why something that is not its driver gets to affect the position
Actually I noticed if I do orient constraint with point as well, it still translates around the driver joint tho this time it maintains the orientation !
Its because the parent is on a different location then the objects pivot. If you delete the point constraint you can see the actual location of the groups child and then you will know how it actually gets constrained using its local offset in that rotated space
i am trying to understand, it just a weird behaviour compared to other constraintsā¦ if i create a group in the same pivot as driven i see same movement around driven object
orient contraint makes it so only driver rotates the driven, parent takes full control but point seems differentā¦ seems as if driven is not exclusive to driver. maybe i am not able to wrap my mind around it or lack proper understanding
is it like, point constraint is only for translate but since i am rotating the driven space, driven object has to move via rotation BUT since its constrained to driven, it can only move by maintaining that offset distance
In Maya āgroupsā are just transform spaces. Any child of a group will move/rotate/scale with the parent groupās channel box numbers. Any additional modification to the childās transform must first take the parent space into account.
In your first clip, the pointConstraint tells Maya to modify joint4.tx ,joint4.ty,joint4.tz to always be 60,0,0 from joint3 , in the parent space of joint4 , which is group1
Since the parent space is rotating, the precise point that qualifies as 60,0,0 from joint3 in that space is changing. Another way to think of it is the direction of joint4.tx is what is changing. If you modify joint4 to display Local Rotation Axes, you will see the red line indicating X direction is changing as joint4 ārotatesā - but of course it is the parent space that is rotating. Any child of group1 will have the same changing X axis.
In your second clip, I donāt believe the pivot of null1 influences the result of pCube2 . Maya pivots are not the same as channel box transforms. The channel box values of null1 still place it at the origin, the parent space of pCube2 is still rotating about the origin. (I think)
@peerke88 @Mambo4 thank you for helping me out ! I now understand more about how point offset works- the offset calculation difference in point and parent !!
No worries. You are right to be so critical in researching how the elements work in their core. Some things do work a bit weird when you start using them outside of the contexts of following what others have done or how they are supposed to be setup.
Once you know all the limitations and edgecases is when you can start making really interesting rigs and components.