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View Full Version : nConstraint connection topology possible in a single node?


wrend
04-02-2010, 06:51 AM
I'm wondering if there is a method to have the kind of component-to-component constraint connection topology seen in the attached picture, in a single constraint node. The extra bit of information is that every one of the points invovled in the constraint will have the same style of connections as shown in the picture (that is, points on the left only connect to points on the right).

Currenty, I can only see this type of constaining being possible with separate nodes, one for each point.... and I'll be having a hole lot more points than shown in the example pic (maybe 1000 or so, and hence the question). Obviously the constraint node would be totally happy with this sort of scenario, its just a problem of how to define these connections to it.

If there was a facility like the 'add to existing' of classic dynamics springs, then it'd be fine. One solution would be to create a particle system for the set of 'left' and 'right' points, weld them to the nCloth meshes, and constrain the two partcle systems. But thats a lot of extra overhead. If you could set per-spring/constraint properties, you migth be able to prune/weight out the constraints that are made internal to the left or right sets of points (the behaviour you get if you just do a constraint between the two sets). But you cant? Another idea may have been to make another two constraints that constrain each set independently, then set these constraints to the opposite strength of the first one (in order to cancel the 'set internal' connections out), but the node doesnt make sense of negative values (perhaps fairly enough).

Don't know, any good ideas?

Thanks.

wrend
04-02-2010, 07:26 AM
perhaps clearer - how do you get the connection topology in this picture, in a single constaint node, with those four selected points?

wrend
04-03-2010, 01:55 AM
I think my best option is to use the connection density range to prune out connections that are of the lengths only found in the left or right sets. In order to do this, I have to setup my real word scene such that all my objects are aligned in a regular fashion, and such that the intra-set connections will be of unique lengths compared to the inter-sets ones. Not ideal, but probably the best I can think of. Still keen to hear other people's ideas...

wrend
04-03-2010, 05:20 AM
Unfortunately, the above method wont work for my case, as Maya's floating precision wont allow me to differentiate between intra- and inter-set connections that are very similar in length (and hence cant be selectively culled due to the precision). Any thoughts?

HowardM
04-03-2010, 09:48 PM
is this for boxes or more complex geo?
perhaps you could make a blend shape where the objects lengths are all stretched out so they connect correctly then blend back to normal?

is it really necessary for those left to right and vice versa connections compared to just left to left and right to right? ;)
what are you trying to really achieve?

wrend
04-04-2010, 03:01 AM
is this for boxes or more complex geo?
Yeah, more complex geo.. the pics are jsut to try and simplify the problem.

perhaps you could make a blend shape where the objects lengths are all stretched out so they connect correctly then blend back to normal?
Mmm, that has some serious potential. Use a hard attract to mesh, and damp everything out, should be good to run the sim by ~frame 4. Luckily I'd want my springs to be 0 length, so it doesn't matter where the points are in realtion to each other when the connections are initially built. Thanks!

is it really necessary for those left to right and vice versa connections compared to just left to left and right to right? ;)
what are you trying to really achieve?
Its necessary. I'm setting up a self-assembly simulation. No pre-imposed guidance/goaling. I've remembered from last time I did this that its best not to use springs anyways, and to just write a custom field of sorts in a dynExpression. If I were to go with springs though, I'd definitely be giving your idea a shot. Cheers.

Castius
04-04-2010, 03:53 AM
If all else fails. Make a mesh that connects everything. Turn off everything but what you need. Then use weld constraint to attach them.

wrend
04-04-2010, 05:02 AM
Ha, I like it, very boy scout. :) It'd probably be a touch lighter to go with two sets of particles and welding them on though (as described in first post)?

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