A challenge with copy SOP and DOPs

[gronk33]

Hi there,

As a relative noob to Houdini I'd love some DOPs advice on a specific problem.

I'm trying to prototype a bike wheel with lead pipes attached to the rim. The wheel is placed horizotally a foot or so off the ground. When it spins the pipes impact anything that comes near.

I've created two object level nodes to represent the contraption - the wheel and the pipes. The wheel is the parent of the pipes.

The wheel is just a torus that spins on the Y axis. It has no dynamics.

The pipes are more complex. Within the object I've got a circle whose radius is driven by the wheel. The pipes are created by a copy node which takes one pipe and copies it to points around the circle. This way I can change the number of divisions in the circle and the number of pipes will change accordingly. And because the circle’s radius is driven by the wheel, if I shrink the wheel, the pipes’ positions will adjust appropriately.

The problem I run into is in applying dynamics to the pipes so that they'll impact objects as individual pipes. I have some success when I make the pipe object a static object – this way the pipes rotate with the wheel and impact geometry. But it appears as if the collision generated by bringing the copied pipes into a DOP is wonky. When I hit play any nearby RBD object fall over.

I’ve tried a whole bunch of different things with no success. I know there is probably an easy way to solve this problem (bringing in copies of objects to a DOP network and having them move with a parent). But I’m missing it.

Thanks in advance!

bike wheel inches v05.hipnc

Edited May 9, 2012 by gronk33

[gronk33]

Apologies - the file I attached was the wrong one - I didn't set up the dynamics. I've attached the correct one to the first post.

Edited May 9, 2012 by gronk33

[sadhu]

Hi. I noticed the following things.

1)Pipes are colliding with boxes when Bullet solver is used. With RBD solver they are passing through the boxes, we are animating pipes. this may be the reason (I am not sure) why they are not colliding with boxes. If you rotate pipes using object position dop till it reaches near the box and then controlling pipes motion by using only angular vel (rbd state dop) then pipes collide with boxes (using rbd solver) and fall down. (But we don't want pipes to dislocate ??)

With bullet solver pipes were reacting with boxes even if their movement is controlled by animated wheel.

2)Converted pipes in to rbd objects, changed the density of the objects. With the density that you had set pipes were passing through the boxes.

bike wheel.hipnc

Edited May 11, 2012 by sadhu

[gronk33]

Thank you Sadhu. By adding the assemble node to the pipe copySOP and passing groups into a fractured object inside the DOP you solved my problem. At least I think that's what solved it!

I appreciate you taking the time to dig into this!