Hello, i'm currently trying to reproduce the automated ik/fk-snap from the autorig-builder. So i was breaking up (and reduced the amount of needed nodes) of such a autorig-builder-setup. It seems to be not so hard although i still not fully understand everything. Before trying to explain what i've found out i'd really appreciate a response from anyone who knows where to find the specific python-callback-function (in general for all) but specifically to trigger the switch (on the worm example the python-callback is available directly on the apex-node as a string). Anyway. Please correct me if i'm wrong but it seems to work this way, that in general there is a custom blend-subnet (3 red nodes) that takes the blend-value, the fk-joint, the corrsponding "ik driven"-fk-joint (orange below fk nodes) for each joint (upperarm, lowerarm, hand). Inside the subnet there is a 4th connection for the rest-position that has no input from the top-level, so i assume it gets set directly in code (which rest-position is it?) ... So the system interpolates between those 2 spaces and not on the ik itself. The ik-setup seems to be straight forward but i still not understand what those "L_upperarm_L_armLimb_rest_global_scale" matrices and multiplications (pink left side -> first 3 inputs of the MultiBoneIK) are used/made for and further more where those matrix-values are coming from. The second thing i don't understand is, what those proxy-transforms (yellow) are doing. Their use is not obvious in the rig-graph and when deleted the switch doesn't work anymore so i assume they have some funtionality used in the hidden python-callback i was asking upfront. Thanks