A simple collision problem

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Hi,

I try to emit a simple geometry and collide them to the bowl but some reason it doesn't work. What Im doing wrong? (See scene)

Mika

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Bowl.zip (319.2 KB)

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Any reason why you want to use the old, moldy Houdini RBD solver? I fixed up your file to use Bullet solver. Used convex decomposition to get the bowl shape, and then used volume sample in the static object for collisions.

As for continually injecting candy into the sim… you have to make sure that the “creation frame” is $F so it continually creates objects, (not only the first frame), and then you don't really want a POP sim feeding into your RBD sim, because the RBD sim should take care of the falling. You just want to “release” the coins from their birth point, (so the particles should only live one frame). I got rid of your POP sim and am just creating points from which to copy coins.

Oh, you also had a lot of object level scales and translations. This makes it a nightmare in DOPs. In general, leave object level scales alone, and do the scaling in SOPs. It can be made to work, it's just messy this way. I got rid of all object level xforms and scales to simplify.
Edited by mrCatfish - April 17, 2019 16:30:41

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Bowl3.hipnc (514.8 KB)

Sean Lewkiw
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Thank you so much, I was able to replicate what you had and got it work! I used RBD solver because all old tutorials, what I found, used it.

I have couple of questions, if you don't mind….

1. You're doing some naming by this attribute wrangle, what is function of that?
2. What is function of Simmed_Candies?
3. Why you added null between delete and copytopoints?

Thanks again! This really helped!
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mihatsu
1. You're doing some naming by this attribute wrangle, what is function of that?
That wrangle node was added by the RBD Instanced Objects shelf tool. You could also simply use an assemble node with “create name attribute” instead. The purpose of this is to give each instance a “name” attribute so that DOPs recognizes each instance as a unique object.

mihatsu
2. What is function of Simmed_Candies?
This is simply to bring the sim back from DOPs. I like to keep all objects seperate so that it's easier to do passes when rendering. You could bring the sim back in the “emitter” obejct, (as the shelf tool set it up), but I find it confusing later, (perhaps months later), to figure out why you're rendering something called “emitter.”


mihatsu
Why you added null between delete and copytopoints?
That null is not necessary. I think at some point while I was playing with your file I was referencing that null in another object… it's good practice to use a null when referencing in other objects. The null can be deleted.

I know it's hard to figure some things out in Houdini when there is such a mix of old and new tutorials kicking around. Sometimes you're fine with an old tutorial, but sometimes things have changed so much an old tutorial is not much help. Here is a shameless plug for my own (free) tutorial on rigid bodies: https://www.lostboys-learning.com/courses/introduction-to-material-based-destruction-and-constraints-in-houdini-17 [www.lostboys-learning.com]
Sean Lewkiw
Lost Boys Montreal
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Thank you so much about your help, this really helped me to understand some basic things!
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