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Author Topic: Folded Security Gate - positioning problems  (Read 1086 times)

Lars Egerrup / LKE Design

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Folded Security Gate - positioning problems
« on: September 16, 2021, 10:54:32 PM »
Hi there,

I have made a Folding Security gate in RC. It is handled by a spline, handling the general width of it - considering changing this to be handled by a numerical x- size as the gate has both a minimal and a maximal width.

The folding gate consist of two pairs of gates, one gate (A) is attached to the column and a secondary gate (B) is attached to gate A. Each side has 3 piston arms and an assembly unit.

The setup consist of a series of L2S generators, some which are nested in each other: COLUMNS and GATES are independent L2S setups sharing the same spline. GATES is assembles the gates, the right and the left, via a mirror modifier. Each gate is made up of a number of L2S generators (Frame, Balusters, spike list, and some of the piston arms) they are all assembled in a group composition so it acts as one unit. Gate B is nested to gate A, so that it can inherit the movement (rotation) of gate A. (See attached screendumps)

Now, it works more or less as planned. It took a while to make all parts act in connection with each other. And I had to use a lot of constants to handle smaller adjustments on the various parts.

I have however still some issues with getting the piston arms to move (turn) correctly. You probably wont notice it on a distance - but it irritates me, never the less.

The gates opens in an angle of max 90 degrees, and the various piston arms rotation is calculated by multiplying the gates opening angle with a factor value for each piston. This doesn’t work completely- and that is most visible when the gate is half open (45 degrees).

It is fairly simple to do in MAX via rigging and the use of various IK solvers, but the price is that I can’t alter the size of the gate. RC solves this problem, but the. I have the problem with the piston arms position when opening the gates.

Do you have any solution on that? Or is it so complicated that it is not worth the effort - and I should just live with having the piston arms a little off in various positions? My trigonometry skills are a little rusty to setup an equation to solve this problem, but maybe other have this skill polished and shinny?


More images, screendumps and a video can be seen at
Lars Egerrup
LKE Design


Paul Roberts

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Re: Folded Security Gate - positioning problems
« Reply #1 on: September 17, 2021, 02:50:08 PM »
Hi Lars,

Unfortunately, RC wasn't designed with the idea of rigging like this in mind. Some basic things can be done using Transform nodes and (as you suggest) trigonometry, but this is quite a complex mechanism that would be very difficult to calculate mathematically. Probably it's much simpler, in this case, to go down the traditional rigging route using Max's IK solvers and then use RailClone to construct the rest of the fencing.

That said I had a go at some of the trigonometry require to get the initial hinges done. As a proof of concept it's OK, but I think it would get very tricky using real geometry.

The file is attached should it be of interest. There are a couple of new Macros included based on the law of cosines that allows you to calculate the lengths of a side and then the angles for non-right angled triangles. They might be useful for future applications so I'll probably clean them up and include them in the built-in macro library at some point.

Paul Roberts
iToo Software