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rbd objects created at runtime ?


ranxerox

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hey all, Is there a way to create rbd objects at runtime and continually feed them into the solver ? I have a scene where I have a bunch of candy dropping into a bowl and I almost have what I want, but it seems like the number of rbd objects is growing too fast. It seems that for every frame, all of my objects are being turned into new rbd objects, where as I would want only the new ones only to be new rbd objects. I have tried a bunch of things, but unfortunately I think I am missing something obvious (I'm a noob). I've attached the scene that I am working on, it's a .hipnc.

basically I use a copy sop to copy the individual candies onto points created in a popnet. Then these are being fed into a rbd fracture object via dopimport.

thanks for any help/suggestions.

-ranxx

candy_bowl15.hipnc

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hey Steven, thanks for the link ! It turns out I was doing something almost exactly like what was described in this faq, however my setup is slightly different, as I don't want instances (the each individual piece of geometry is slightly different), so I can't use the rbdpoint dop. I almost have what I want, but I'm in this situation where it seems like I'm birthing 2 rbd objects at the same place every frame, whereas I only want one (or perhaps 2 at different places). Any chance you could take a look at my scene and see what's wrong ? It's soo close but I can't see it.

I've attached my latest version.

thanks

-ranxx

Hi,

This thread has a link to the DOPs FAQ on the SESI exchange. In the FAQ, look for number 18 - "How do I get a particle network to birth objects in a DOP Network?"

Hope it helps!

Cheers!

steven

candy_bowl18.hipnc

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hmmm, I think I've narrowed down the problem somewhat. My particles are being used by the copy sop to put geo onto them, which are then being used by my autodopnetwork to create rigid bodies out of them. If I just look at the points of the pop net, each point seems to live for 2 frames (I want to see only 1 particle alive at each frame). This happens even though I've set the lifespan to 1/$FPS. I've tried lowering this to 1/(2*$FPS) and there are still 2 particles visible at every frame. Is there something I'm missing here ? I want the particles to be alive only on 1 frame.

thanks

-ranxx

hey Steven, thanks for the link ! It turns out I was doing something almost exactly like what was described in this faq, however my setup is slightly different, as I don't want instances (the each individual piece of geometry is slightly different), so I can't use the rbdpoint dop. I almost have what I want, but I'm in this situation where it seems like I'm birthing 2 rbd objects at the same place every frame, whereas I only want one (or perhaps 2 at different places). Any chance you could take a look at my scene and see what's wrong ? It's soo close but I can't see it.

I've attached my latest version.

thanks

-ranxx

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yes, just wanted to follow up on this. I got it working the way I wanted. I had some weirdness where the kill pop and particle lifespan was acting in a counter intuitive way which I don't understand really. According to the dynamics faq, you want your particles to last for 1 frame only. It suggests using either a lifespan of 1/$FPS or using a killpop and testing age against 1/$FPS to kill your particles. Both of these methods let the particles live for exactly 2 frames (well, they were visible for exactly 2 frames inclusive). I tried a number of things to fix this (including lowering the time to live to very small values, tried oversampling etc.). In the end if I changed the rule on the kill pop to kill all particles (1), then the particles were only visible for 1 frame. This doesn't make much sense to me. I thought if my kill pop was set to kill all particles then these particles wouldn't be visible at all. I guess I have a long way to go to understanding this package. However it is strange that the suggestion in the dop faq didn't work.

-ranxx

Yes, you figured out what the problem is. The solution is to append a Kill POP to the Source POP & that will ensure the particle exists only on that frame.

Cheers!

steven

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