This is the twenty-second entry of 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 21, I posted an update on the new Houdini 15.5, which included a lot of excellent improvements in the modeling part of the application. I also wrote that I was starting on a new series of modeling tutorials from gametutor.com, which has a particularly good focus on the Houdini to Unity game pipeline with lots of free tutorials.
Gametutor.com Tutorial: Creating a Procedural Bookcase
This particular tutorial is for beginners and is just under an hour long and consists of 5 lessons. I finished the intro and first lesson, which was primarily getting the work environment in Houdini set up.
One thing that is interesting in Houdini is the ability to create "Houdini digital assets" (HDA), which are special to Houdini and can be very helpful in creating assets for a game you are creating. Making this bookshelf a digital asset allows me to re-use anything in the model for other projects. It is also very convenient for storing and exporting your assets to other applications. Lester Banks has a good introduction to HDA for Houdini on his website here.
Lines and Expressions
This tutorial uses lines initially to set up the shape of the bookcase. Then, using an expression, the tutorial shows you how to make the line parametric, meaning that when you manually change one side of the line, the other responds accordingly and adjusts. It's really quite simple, but it looks hard.
Once you get the top/bottom and sides of the bookcase, the tutorial shows you how to use an extrude node to expand the line into board-shaped geometry.
The Subnet in Houdini
This is the first I've come across the idea of the subnet. This means that you take a collection of nodes (in this case the bones of the bookcase) and turn them into a subnet which looks like an individual node, but is actually the complete layout of nodes used to created the bookshelp shape. The reason one might use a subnet is to save space and make your node layout a lot cleaner.
SideFX has a nice tutorial on creating a "digital asset" which also has a section on subnetworks. You can catch the tutorial here.
Next up: Part two and three of the Bookcase Tutorial from Gametutor.com