Tutorial 4 Part 2 - RBD and Bullet Solver Confetti

October 17, 2018


Welcome back to part 2 of our Confetti Cube Tutorial! In this tutorial, we go over converting our cube geometry into a dynamic RBD object that bounces around. Once we have done that, we go over how to emit points from the areas that have velocity. Those points are then used to feed confetti geometry into our bullet solver which deals with the confetti interaction. Enjoy!




The first section of this tutorial doesn't require too much explanation. We convert our cube into a Rigid Body object and run it through a 'Rigid Body Solver'. This allows it to become dynamic.


The part that may be confusing is why we use a pop-net to emit points which die immediately and then convert to geometry and pack them. We pack the geometry so that we can use a bullet solver with an RBD packed object. Now, we could just use a pop-net to run the full confetti simulation, but, they won't collide with each and won't stack. I tried using a grain-solver to stack confetti but the problem is that the grain solver uses a sphere shape as a collider and so that would cause our confetti to inaccurately interact with each other. Instead, we use a pop-net to deal with color, velocity and emission whilst the bullet-solver deals with collision and interaction. In a way, the pop-net merely sets up the necessary attributes to be used by a bullet-solver.


Below you can see how the two work together:

We create particles which each have velocity and color attributes. They have a life expectancy of 0.01 second/less than a frame. 


We copy geometry to each of these points. Because we will be passing this geometry into a bullet solver, we need to pack these points as that is what is required by the solver. The easiest way to pack points is by using the ‘Assemble’ Node.


We pass these points into the Bullet solver. The original points die due to their low life expectancy but the ones passed into the bullet solver will continue to persist in the simulation using the attributes that we had on the original points. 


 Here you can see that as the packed geometry is passed into the bullet solver, it becomes dynamic and interacts with other geometries.


Fortunately, the bullet solver is extremely fast when calculating simple collisions. With geometry as simple as confetti, the bullet solver is incredibly accurate whilst being very fast.


This tutorial is quite straightforward but if I forgot to cover anything, please comment with your questions down below or on YouTube and we will get to answering them. Thanks for watching, that's all from this tutorial. We might only have a tutorial two weeks from now as we are busy on three tutorials simultaneously. To keep up to date, subscribe to us on YouTube or like our Facebook Page 

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