How to set bone rotation in Python script by an absolute value?

Question

I am writing a simple Python script that creates an animation. In order to do this, I am using the following code:

def RotateBone(boneName,rotDegrees,rotAxis):
    boneSelect = bpy.context.object.data.bones[boneName]
    boneSelect.select = True
    bpy.ops.transform.rotate(value = radians(rotDegrees),axis = rotAxis)
    boneSelect.select = False

It rotates a bone and then I use lock key frame command.

My problem is that if I run it twice, it will re-apply the rotations on the animation sequence. That makes the process of development tedious. I am deleting the human model and re-loading it from disk by using the UI, then I use Run script command.

I've also checked this answer, it does the same - relative rotation. I've also tried setting the rotation_euler property of the bone directly, but it does not seem to do anything. Any of these might solve my problem:

• Find a command that resets all rotations in all key frames that I did.
• Set the bone rotation values in an absolute way
• Find a command that deletes an object and a command that loads .mhx object from disk.

Any idea?

Answer 1

Your problem was using the edit bones, not pose bones.

A function I used was like the following:

set_rotation(ob, bone_name, rot, axis='X'):
     mat_rot = mathutils.Matrix.Rotation(radians(rot), 4, axis)
     bone = ob.pose.bones[bone_name]
     bone.matrix = mat_rot

This has the added benefit of using a quaternion I believe. I will need to look into that. axis can also be a Vector.

Answer 2

I think I managed to find a solution. rotation_euler property does seem to work (and it is absolute). It didn't work before because rotation_mode was quarternion, so it didn't affect them.

Thus, the solution is:

def SetBoneRotationDeg(human,boneName,rotEulerDeg):
    lastMode = human.pose.bones[boneName].rotation_mode
    human.pose.bones[boneName].rotation_mode = 'XYZ'    
    human.pose.bones[boneName].rotation_euler[0] = radians(rotEulerDeg[0])
    human.pose.bones[boneName].rotation_euler[1] = radians(rotEulerDeg[1])
    human.pose.bones[boneName].rotation_euler[2] = radians(rotEulerDeg[2])
    human.pose.bones[boneName].rotation_mode = lastMode