nCloth collisions and deformations question...

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Old 02 February 2008   #1
nCloth collisions and deformations question...

Hello out there.

I am determining whether nCloth would be a good tool to create deformations upon collisions (crashes). It seem a very suited tool for the task. I intend to use nCloth as low-poly mesh deformers to drive higher res models... I have a few issues and questions I am hoping you might be able to help me with.

I wish to translate nCloth meshes without the use of dynamic forces; but instead, passive nCloth objects. Yet, when I first "push" my deformable nCloth, I do not want it to deform. When it hits the target, I do. Is this possible? I tried keying the rigidity, deform ressistance, and input mesh with very poor results. To illustrate I am inclusing a simple basic test file.

Any help/ideas/experiences that involve something similar are greatly welcomed.

Thanks much,

Jim
Attached Files
File Type: zip deformation_00.zip (8.5 KB, 11 views)
 
Old 02 February 2008   #2
You can translate it with the input mesh attract at around 1.3( for no flexing ) then suddenly key it to zero to release. It should continue along in the motion imparted by the input mesh attract. Keep the rigidity and deform resistance at zero. To make the car like metal make the stretch/compression/bend resistance value all high. Also make the substeps at least 1/10th of the stretch resistance value. To allow the metal to crumple with memory make the restitution angle around 7. This attribute controls the angle at which bending starts to change the rest angle. Play with it to get the best value for your object. If you need some areas to remain particularily rigid, you could select the cvs and create a component to component constraint, setting the contraint to maxDistance and adjusting the distance to get a desired density of rigid connections.

Duncan
 
Old 02 February 2008   #3
sweet been tryin to get this , id get the crush then it would flex back to the orginal position
 
Old 02 February 2008   #4
Yes, attributes like deform resistance don't work well for this because the material becomes more like molassis, slowly deforming over time due to gravity. The restitution was added in order to support denting metal. Unlike the rigidity attributes it is a local effect, and thus requires the use of stretch/bend/compression resistance. For a detailed model one will need very high settings, and high substeps to keep the material fairly rigid. One could use a lower res cloth as a wrap deformer for a detail mesh, but one will get much more interesting crumple effects by simulating on a high res mesh.

Also note that the self collision should probably be set to surface and the collision thickness should be relatively low compared to the triangle size, to allow it to crumple with detail, although it depends on the desired effect.

Duncan
 
Old 02 February 2008   #5
Duncan, thanks very much for replying.

Wanted to share today's tests results: I tried keying the Input Mesh Attract attribute, and increasing the substeps. The keyframing part seem a little bit tricky. In my case, turning the mesh attract to 0 does not seem to give momentum to the output cloth mesh in the direction I am translating the input mesh.

I put a collision wall between the input mesh and the cloth mesh. I then translated my input mesh to go through the wall. As the collision occured, I keyed out the input mesh attract. That seem to work...

I also tried transform-constraining the cloth object. I created a locator and keyed the locator to collide with a wall (This time not "thorugh" the wall). I turned the constrained strength from about 20 to 0 in one frame (the collision one) and I seem to get good results.

I was wondering if you had any thoughts on the ability to lock the motion (or minimize it) after an object collides. As a part of a bigger vehicle, after the deformation occurs, the cloth would still need to be pertain to it, and the vehicle would dictate the cloth's position.

Thanks much.

PS: My zip files are in reality RAR files
Attached Files
File Type: zip constraintDrivenMesh.zip (117.8 KB, 31 views)
File Type: zip inputAttractDrivenMesh.zip (105.3 KB, 20 views)
 
Old 02 February 2008   #6
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