In this video, Scott Pagano explains the scene used for the Impacts chapter. Learn techniques for preparing source geometry derived from rigid body simulations for particle simulations in Houdini.
- [Instructor] In this chapter, we're going to take a look at emitting particles off of object destruction. So we have a scene called objects here built. And we're just going to dive in there so I can show you what we have going on. Up top here, we have the actual geometry being built and then we have the dynamic simulation run and built in cached out and all that stuff is ready to go, and that was all cached out into this DYN_SIM_01 node here. And, that has a couple different things, and the one I really want to point out mainly is that besides just obviously just caching out, what's coming in off the DOP IMPORT nodes, I've also created a DOP IMPORT records node, and you can see that that is pointing to our simulation, and I'm looking at a specific object, the ground, and then I've manually put in the data path and record field, this variable impacts.
And so what we can do from that, is we actually can get out points that represent when things impact that object, the ground. So if I go down here to out impact points, I'm blasting out just those here, I'm going to play this back... You can see we have the object template, and then you can see that we have these points that get generated, when the object hits the ground. And we're gonna use these to generate some particles. And we're going to do some filtering on these as well, so we can filter some of them out. Because you can see that they still kind of remain there even after the main impacts have happened.
But this is a great starting point for particle emission, for doing, sort of a, object destruction particle scene like this. And the next thing I want to point out in here is that we're using packed geometry, but I've got another chain here where were blasting out the actual packed geometry from the SIM, let's go find a frame here, and I'm going to un-template this _out [Null] here, so that isn't mirrored over that. And then I'm going to unpack that geometry, delete out some attributes, use a trail to add some velocity, and then the main thing here I want to point out is this debris source node.
This is sort of like an uber node, where there is a lot of stuff under the hood, that can basically take the input of a simulation like this, and give us points on the edges when objects separate. And so I've cached that out already as well, because it can take a little bit of time to run that SIM and we want to focus just on the particle side of everything. But I wanted to show you some of the techniques I used to generate the source material. These are really useful for these kinds of projects. So I'm going to rewind to the beginning here, I'm going to click the _out [Null] here for the debris points, and we're going to take a look at what this debris source node gives us.
So you can see, it's almost like we have this ghosted outline of where these object pieces are separating, as you can see, this is going to be great source material to use as emission points to generate some particle, like sparks and streaks, coming out of this object getting destroyed. So once again this speaks to the fact that with any good particle simulation, really focusing on what our source is, is almost just as critical as what our simulation is. You can see I've created multiple different elements here. We've got out impact points, and our debris points, to be able to generate simulations off of both of those to generate a rich, final result.
Okay, so that's the overview of the scene, and next we're going to dive into creating the particle source objects for our particle simulation.
- Working with sprites
- Adding POP Color and POP Wind
- Creating a particle source object
- Creating volume noise
- Creating trails
- POP Collision Detect
- Instance node