Cloth and wind resistance

Normally a cloth like this:

would just fall and retain this exact shape... I put together a little force using the field force DOP and a little sopnet to get a basic simulation of wind resistance as it falls.

The force is applied along the normal, opposing the velocity. It is also scaled by velocity.

Here is an example:

Blue is the point normal, green is the velocity and red is the force to be applied.

This is far from correct but it works alright in practice.

This cloth is 2m x 1m and low density (less than a kg total I think)

hipnc file is here!

Comments

Some SOPs edges and poly line business

Every time I go to extract the border from a mesh I always end up using some strange combo of Group unshared edges, delete and dissolve, I came across a good way of getting unshared edges that I haven't thought of before, and now it seems really obvious ... using the polycap node to trace the border and then deleting all of the source prims, works like a charm! I have also usually had trouble with splitting up a line into multiple primitives, here is a way to create a primitive per edge. This example only works if every point has 2 neighbours but could easily be modified with a copy SOP to allow a dynamic amount of neighbours. (instead of 2 vopsops and a merge to duplicate the points). It works like this: The point number is stored in an attribute to create a unique number for each point The whole mesh goes into 2 streams to duplicate every point. For the first set of points, each point gets the point number of the first neighbour and applies a cantor func...

Worm locomotion with FEM

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Wire to RBD feedback in DOPs

Normally if a wire is constrained to an RBD, the rbd isn't affected by the wire at all. Which is annoying ... but I had an idea to get it to work. the wire solver can store the internal forces on the geometry. In DOPs I made a point force, the position is set to the position of the constraint and the force is the wire's internal (linear) force. I have put a sopnet in the dopnet to get the wire and the constrained point so I can reference them in the point force. It could be simpler with a python expression to get the position and force directly without going through the sopnet, but this is just a little test... For multiple attachment points, I think a copy data node could be used to copy the point force data for each constrained point ... hip file here Wire to RBD feedback forces from Sam Hancock on Vimeo .

I, Houdini

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