Bone projecting another bone to the ground?

Hi there,

I have a rig problem which boils down to following problem I cannot solve.

I want to have one bone fixed on the ground (or better, another specified height) with another bone’s position and orientation determining where on the ground:

So the smaller bone is supposed to stay on the ground. However, the bigger bone points at the position on the ground, where the smaller one shall be, projecting into onto the ground.

I know, this is easy if you are free to move the ground bone and have the other bone track it; but unfortunately the position of the big bone is driven by other factors, thereby I have to solve the situation the other way around.

Any ideas for this? Thanks for any hint!

One way. You need another bone. Use two floor constraints and a parent bone without inherit rotation on the child. I think this is what you want.

pointer.blend (552.1 KB)

Hi, you can use a shrinkwrap constraint in project mode (choose Y axis in local space because it is the longitudinal axis for bones), targeting whatever mesh object, such as a plane. Then rotate the parent bone to point at the surface.

Thanks a lot for the quick help, you two! I was not aware of either those two constraints, tbh… :slight_smile:

@stilltrying Unfortunately, this is not quite what I need, I need the projected bone where the pointer points to, like where the red part is:

Maybe projection is not the correct term for this.

@Hadriscus This is the solution I was looking for! For others (or my forgetful self later), this is the setup that works for me (there is a plane on the ground which is not visible on this orthographic view):

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