On the top left of my Poser 4 screen is a row of icons including one for "chain break"? What does it do? What is it for? How to use it? I have been making a Poser model of a UK-made type of industrial and diving oxygen rebreather set called a Salvus (made by Siebe Gorman). It has a long breathing tube that runs from a kit pack at the left waist to a breathing mask. It has 15 segments, 0 to 12, and of those 1 to 12 are an IK chain, and 1 to 11 are curve. I know how to long to make it, as I have measured a real one. In Poser I run into two snags with it:- (1) Sometimes Poser routes it so it goes through the flesh of the man's left arm and so I need to reroute it a bit without the job being like wrestling with an angry python. Can I use "chain break" here? (In reality the man's arm would push it aside a bit.) (2) In some positions of his head, the end pulls of the mask because it won't quite reach. In reality the tube, being rubber, stretches a bit. I would like to be able to tell Poser that, it such and such an IK chain can't reach whatever its goal is inkyParented to, scale all the chain members a bit along the direction of the chain. (I suppose I could slave all the segments' yScale's to one master parameter dial "lengthen breathing tube", but there is a bug that often makes slaved morphs obey the right named master in the right named part in a wrong model, because the slaving mechanism doesn't keep track of models being renamed on loading when there is already a model on stage with the same name, and I may want to put two divers with Salvuses in the same scene.)

The chain break tool is used to limit how far IK propagates. I almost never use IK in poser, but the tool can be used so that moving the hand will only move the hand and forarms, not moving the shoulder. Assuming IIRC, that is.

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I just tried chain-break. While chain-break was on, clicking the figure peppered it with tiddleywinks with the broken-chain symbol on, instead of selecting a part, but it seemed to make no difference to how an IK-chain behaved, even if I put one of thodr tiddleywinks on a segment part way along the IK-chain. It seems that we need a proper fullscale tutorial about chain-break.

Look at page 120 of the poser 4 manual. It seems like a fairly clear explanation.