I'm trying to rotate a model about a specified axis and origin (preferably in global coordinates). I would like the rotation to be applied on top of whatever transformations have been applied already. I've looked at the documentation, including the programmer's FAQ and the source code for ConstrainedMove. I couldn't figure out how to do this, so I wrote the following function based on the ConstrainedMove code to do the rotation relative to another model: def rotate_around_model_axis(ref_model, model, origin, axis, angle_deg): mvo = apply(chimera.Vector, origin) vo = ref_model.openState.xform.apply(mvo) mva = apply(chimera.Vector, axis) va = ref_model.openState.xform.apply(mva) xf = chimera.Xform() xf.translate(vo) xf.rotate(va, angle_deg) xf.translate(-vo) model.openState.globalXform(xf) But, this doesn't seem to work as I'd intended. Is there a way to do this? Also, I'm a little confused about the coordinate system. It seems like the concept of a global coordinate system may not apply in Chimera the way I'm used to (like in Amira for example) since the camera is fixed. Is this true, or am I totally lost? Thanks in advance for any help you can provide. Jordan