Learning Houdini Journal 14: RBD Objects | Finishing Up

Feb 13, 2016 at 11:54 pm by -gToon

This is the fourteenth entry of what will be a year-long journal on learning the 3D application Houdini, created by Side Effects Software. Houdini is a sophisticated application that is widely used in the production of visual effects for Hollywood films such as Big Hero 6, Mad Max: Fury Road and many others.


In my previous Learning Houdini Journal 13, I created the window that the car will crash through and learned out to use the shatter tool to fragment the geometry. The next step is "to convert the fractured geometry into a set of dynamic objects"

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The new nodes added to the network after applying the fracture node

RBD Packed Object
As you can see from the Houdini node network above, the steps leading to the Voronoifracture node are, convert to fog volume and chunk centers. I'm not completely sure what these nodes mean, although John Moncrief in the Intro to Houdini 15 course I've been following, explains what they are. I just don't know why these steps are necessary. I'm sure this knowledge will come as I get better with the dops nextwork in Houdini.

At this point, we have selected the shattered window. Now all we have to do is to look under the "rigid bodies" tab at the top of the interface and select the RBD fracture object. Now Houdini asked us if we want to create an RBD packed object or an RBD fractured object. Strangely, it's the packed object we want to choose as the fractured object is one that works in context with other dynamics like liquids.

Shatter Node
Which fracture object to select?

After applying the RBD Packed Object node, we now have a new "window" in the dop network for the project. Checking the parameter inside of "window" we see we can adjust the amount of objects in the fracture. After experimenting, I came up with 350 pieces of glass. This worked because it sent a lot of objects flying as the car impacts and shatters them. And what's neat is the since the window is plugged into the dops network of nodes, it inherits all of the other objects dynamics (friction, etc.).

Here's a small clip of what the final dynamic animation of the car accelerating through the window and shooting out on to the street below looks like:

What I've Learned So Far
I've finished the 45 lessons from the Introduction to Houdini 15 at pluralsight.com. In the lessons I've learned the following skills:

  • overall layout and structure of Houdini 15
  • how to work with nodes (creating and adjusting them)
  • geometry creation
  • hdri light set up
  • importing geometry
  • expressions (specific to Houdini)
  • dynamic animation
  • Houdini network structure and functions
  • camera set up and manipulation
  • fracture/shatter tools and RBD objects

I could make this a longer list, but these are the essentials. The Intro course (well-taught by John Moncrief) has given me a basic foundation to start more specific and focused learning of Houdini 15. I'm intrigued by the Dynamics networks in Houdini 15, but I want to work more on modeling and geometry. Houdini isn't known to be a modeling program, but I like what it can do. I don't think Houdini is any less efficient that, say, Cinema 4D, when it comes to modeling, but I don't have enough experience yet to be sure. It's just a hunch.

Since Rohan Dalvi has just come out with new training last week that uses a lot of modeling, I'll be moving to his tutorial next. For now, I plan on reading a bit more in the manual about geometry. Here's the trailer he created for the course:

Procedural Vehicle Modeling - Trailer from Rohan Dalvi on Vimeo.


Next: Starting Rohan Dalvi's Procedural Vehicle Modeling Tutorials


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