Null Moves Along Multiple Axis, Instead of One?

[Atom]

Hi All,

I have a NULL inside a RIG which controls the eyebrows. I have made a slider that allows me to raise the eyebrows. But when I change only the Y axis of the NULL, it moves along the Z axis as well. Is there some way to make that NOT happen?

I am using a .set() on the py parameter.

node.parm(parm_name).set(value) 

 

Edited December 30, 2016 by Atom

[edward]

The axes (ie. space) that the T/R/S values operate on an Object depends on its "parent" (ie. input) and any pre-transform it may have. So if your null has no parent, then you just need to reset (or "clear") the pre-transform that the null has to reset its space back to world. If it has a parent, then your pre-transform needs to be the inverse of the parent's world transform.

[Atom]

Oohh, so how do I handle that in a rig? This NULL is at the end of a long chain. Is the last parent the only one I need to invert? It also looks like the NULL has it's own rotation as well...

Edited December 30, 2016 by Atom

[Atom]

I am basically returning to a problem I was not able to resolve back in August. All of my rig controls generate offsets from an original saved state. This way I can zero all the controls and return to the default pose. So internally I grab the original value from the saved state then alter it based upon the slider and store that as the new TSR on the control object which happens to be a NULL.

I was able to craft a function, from the help I received back in August, on projecting a distance along a vector but this does not take into account any parenting.

Also all I get back is a matrix which I am not sure how to apply to my saved matrix?

def projectAlongOrientation(node_path, node_name, distance, passedVector):
    n = hou.node('%s%s' % (node_path,node_name))
    if n:
        # Fetch the original starting value from saved parameters.
        try:
            rx =n.parm("r_%s_x" % node_name).eval()
            can_continue = True
        except:
            can_continue = False
        if can_continue:
            # If the first parameter exists we'll assume the others do as well. (assuming often leads to crash)
            ry =n.parm("r_%s_y" % node_name).eval()
            rz =n.parm("r_%s_z" % node_name).eval()
            tx =n.parm("t_%s_x" % node_name).eval()
            ty =n.parm("t_%s_y" % node_name).eval()
            tz =n.parm("t_%s_z" % node_name).eval()
            
            # Construct matrix parts.
            mtx_rot = hou.hmath.buildRotate((rx,ry,rz),"xyz")
            mtx_loc = hou.hmath.buildTranslate((tx,ty,tz))
            
            # Create world transform.
            mtx = mtx_rot * mtx_loc
            
            v = passedVector
            direction = v.normalized()
            vector = direction * distance
            translate_matrix = hou.hmath.buildTranslate(vector)
            mtx_result = translate_matrix * mtx
            #n.setWorldTransform(mtx_result)
            return mtx_result
        else:
            print "projectAlongOrientation: expected source parameter [r_%s_x] not found, you need to click the Capture Original Values button." % node_name

mtx_new = projectAlongOrientation(node_root, "oculi01_L", v, {0,1,0})     

So in this case for the eyebrow lift, I only need the Y translation value from the resulting projected matrix?

What does the python code look like to extract Y from a matrix? I already tried...

new_y = mtx_new.y

 

Edited December 30, 2016 by Atom

[edward]

Sorry, I don't have Houdini right now but the process is roughly:

parent = n.inputs()[0]
parent_rot_inverse = hou.hmath.buildRotate(parent.worldTransform().extractRotates()).inverted()
n.moveParmTransformIntoPreTransform() # easy way to clear local parms since we're going to overwrite the pretransform
n.setPreTransform(translate_matrix * parent_rot_inverse) # where translate_matrix is the local offset translation matrix