Learning Houdini Journal 06 - Expressions and Workflow
Staff Writer By: Ricky Grove (gToon)
This is the sixth 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 5, I discussed my progress with Polygonal modeling in the Pluralsight course I'm following along with some insights into Expressions and Houdini workflow
Polygonal Box Modeling
I learned about the two types of basic modeling: Box up modeling and Curve Up modeling. Box Up modeling is where you start with a primitive shape (sphere, box, cone, torus, etc) and then build the model by extruding, extending, cutting and shaping your basic shape. The Curve up is similar but uses a line or curve that you create geometry from. It's more complex than that, but I'm doing basic Box UP modeling so I'll focus on that.
I learned the Bridge Node, Cap Node, Transform Node, Edit Node, Extrude Node and finally the Merge Node. All of these are found in the main shelf under the Polygonal tab in the Houdini interface. They can also be invoked using Tab>Select Node Type>Place in Network quite easily. Houdini makes it very easy to work either directly in the network pane or, if you select a specific node tool on the shelf (like Extrude) it will automatically lay the node down and link it in the network you've created. Pretty neat.
It occurred to me while working on the wheel using the various nodes that perhaps modeling and other activities in Houdini 15 are a combination of direct selection of tools and laying down specific nodes in the network you've created. We'll see if this idea proves to be true as I get better and using Houdini 15
Although somewhat dry, this is an accurate description. My instructor, John Moncrief, laid it out while we were trying to copy one parameter from a node to another parameter. Expressions (i.e. parameter expressions) was the way it worked. Expressions are created using Hscript (default), python or VEX. I suspect Expressions will become more important as I progress in Houdini.
Understanding Procedural Workflow
I was also quite interested to see how to take a long string of nodes in a network and create a large overall node to contain them which makes for much easier use both practically and visually in the network pane. However, an interesting problem came as a result of the merge of the wheel and car node networks: we had problems with normals and uvs. One side of the network had normals, but the other side didn't so the merge node had stripes across the center indicating something wasn't right. Middle-click the node and you can see exactly what the problem is and take steps to fix them. When you get both sides with the same attributes, then the red lines disappear and you can move on.
Repeat Remember Repeat
PS: Cyber-Monday was great for Houdini learning. I picked up Rohan Dalvi's "Tea and Cookies' Houdini course for 40% off. Thanks, Rohan!
Next: Finishing up the Introduction to Houdini 15 course.