View Full Version : nCloth constraint bend not working

03 March 2010, 06:03 PM
I'm working in 2009 and testing bend resistance with constraints. Bend resistance is having zero effect on the simulation.

Anyone know if this is a bug? Or is bend resistance only useful for certain types of constraints.

03 March 2010, 04:15 PM
You learn something every day. It has no effect on any constraint made with vertexes. BUT I had no idea nCloth would make constraint with edges and faces. So if you want to use bend you need to select edges. Otherwise it has no affect. Well that's not true it will still slow down your sim. :shrug:

03 March 2010, 05:35 PM

is this documented?!

i did one day, by accident, select edges and made it a constraint, but i figured it just converted it to verts and made the constraint...

03 March 2010, 05:45 PM
I had never read anywhere about nCloth constraints using edges or faces.

But when i read the docs on bend
bend (bnd) bool false
For edge-edge constraints this controls whether we constraint the bend permitted across those edges.

Reading "edge-edge" made me think that i had never tried selecting edges when making a constraint. After trying it i proceeded to smack my forehead.

03 March 2010, 09:11 PM
In nCloth we support all the permutations of connections of different component types:
point-object (point to surface)

Point to object can be thought of as a special case of a point to face connection. Note that currently (object-object, object-edge and object-face) are not supported, but the UI for component-component will interpret these selections by replacing the object by all its vertices.

Each of these has different behaviors.. for example with face-face when one face is rotated the other will move as if it is rigidly attached. Edge-Edge constraints are free to hinge unless the bend resistance is used. The tangent strength on the nComponent node has no effect for point-point constraints because there is no sense of surface normal... just distance between the points. However for constraints to a face or a surface it controls the stiffness of the link in the direction parallel the surface.

Bend stiffness requires an edge-edge connection. Potentially it could work for an edge-face connection, but currently it doesn't. And as mentioned it still slows things down even for unsupported types, so keep the constraint bend off unless using it with edge-edge.

I'm sure most of this exists in some form in the doc, but I'll enter a doc bug all the same.


03 March 2010, 11:05 PM
Cheers for the never-ending knowledge! :)

03 March 2010, 01:00 AM
Thank you Duncan for the clear and easy to understand description of this aspect of nCloth. This is always welcome, as is you presence on these forums. You have made working with nCloth way more accessible to many users. Thank you. :buttrock:

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03 March 2010, 01:00 AM
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