Learning Houdini Journal 13: Windows and Shatter Nodes
Staff Writer By: Ricky Grove (gToon)
This is the thirteenth 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 12, I discussed how I fine-tuned the motion and the impact of the race car in the tutorial scene I'm using to learn Houdini. In this entry, I'll go over adjusting the window the car will crash through as it flies through the air to the road below.
The aptly named "Blast node"
Getting the Window Ready
The next part is something I still don't quite understand. The instructor, John Moncrief, stated that it was necessary to "move the window geometry out of it's larger City Block node into its own geometry container". In order to do this, it will require creating two window geometry nodes: one with just the window and no City Block, and one with just the City Block and no window.
I understand the need to isolate the window from the building geometry in order to shatter it without affecting the larger City Block set, but I don't quite understand why two different versions have to be made.
Using the Shatter Tool
Once the actual window geometry is created (extrude node), it's a simple matter to apply the Shatter node to the geometry. Note that this new window geometry is at the Obj level along with the other major nodes like the car, the wheels and the City Block set. The default settings look good, but I'll be doing some fine tuning on the parameters of the shatter in the next journal.
At this point, I've got the car bursting out of the window, shattering the geometry and hitting the pavement below.
Fracture, Shatter and Break Things in Houdini
Sidefx has a good (if too short) introduction to RBD fracturing (what's the difference between shatter and fracture?) which is easy to follow. I also found Deep Shome's Voronoi fracture tutorial on YouTube, which is quite helpful. Finally, I ended up at Atom's Vimeo channel and found many interesting Houdini tutorials there.
Next: Fine-Tuning the Window and Working the Crash Animation