Is it possible to move a bone toward/away from its origin point?

CrissieB

Hi all,

I'm creating a riverfront park set with a city across the river. I've created a custom cityscape and I would like to rig it so users can easily move the cityscape to be in-frame for a variety of camera angles. I know I can rig the cityscape bone (a partial cylinder) with its origin at the scene origin, so Y-Rotate will slide it around an arc centered at the scene origin.

I'd also like to be able to slide the cityscape closer/farther from the bone's ... to change the radius of that swing arc, without changing the scale of the image.

Is there an easy way to rig that change-radius for a single slider? If the swing-slider (Y-rotation) is at 0, the radius line (from the bone origin to the center of the cityscape) will be directly on the Z-axis. But if the swing-slider is not at 0, will a Z-translate move the cityscape along the bone's local-Z (directly toward/away from the bone's origin) or the global-Z? Is there a way to set and lock that?

Thanks,

Crissie

 

Syrus_Dante

Create two bones one in the center and one child bone for the offset regarding the center. The first stays in the center and controls the y-axis rotation, the second child bone is for the translatonal offset that also should get full weightmap influence on the cylinder. Lock and hide the transfomer properties that shouldn't get dialed by the user or create Rotate and Offset properties in the root of the figure and link the actual bone y-axis rotation and offset z translation to it with ERC-Freeze like a pose controler.

CrissieB

Hi Syrus,

I'd thought of a three-bone setup -- GroundPlane > PivotArm > CityScape -- which I think is what you described. The PivotArm would have its origin at the scene origin and its end point at the CityScape. Y-Rotating the PivotArm would swing the CityScape around an arc. Scaling the PivotArm would change the radius, moving the CityScape closer to or farther from the scene origin.

I was wondering if there was a way to do that without a third bone. I guess not.

Could the PivotArm could be a ghost bone, without any modeled geometry? And yes, the visible controls would be in the GroundPlane bone, via ERC Freeze.

Crissie