Saturday, September 8, 2012

The tools from which everything else is built

In my quest to learn all of Houdini's 252 Geometry tools, I have explored the 32 node types listed in the Manipulate submenu.

Above: the Manipulate submenu.

I thought these would just be steps 9 through 40 of a long and boring quest of knowledge, but no! I discovered some very important tools in there, and I might never have discovered them if I had not tried to learn every single one of them.

The best example of a well hidden gem is the SSS Scatter node. Neither its icon, its name, or even its documentation gives any indication of what it does.

Poor SSS Scatter probably doesn't get much use.
Its icon hasn't been updated to the new style...
and its documentation is pink, for some reason.

If I wasn't trying to go through the entire list of tools, I would never have tried the SSS Scatter node. When I want to implement a particular effect, I look through the list of names, trying to guess which one could help me; but "SSS Scatter" never sounds like what I am looking for, regardless of what I am looking for. So, what does the darn node do, anyway?

It gives chickenpox.

It creates points all over the object's surface! Very useful-looking. I hope that, among the remaining 212 nodes, there is a version which creates points all over an object's volume, too.

The other reason why there are some useful nodes which I wouldn't have discovered otherwise is that so many of those nodes are redundant. There is a Twist node, for example, which does exactly what it says on the tin. Many 3D packages have a Twist modifier, because in those packages, that's the only way to twist objects; in Houdini, however, twisting an object doesn't need to be a primitive operation.

Twisting is a simple mathematical transformation, whereby points are rotated around an axis by an angle which varies along the length of the axis. I could implement that using the Point node, which applies a mathematical formula to each point of an object. Of course, writing a mathematical formula is much harder than using a pre-existing Twist node; the point is that being able to write any mathematical formula is much more powerful than having to pick among a list of pre-existing nodes. It's the powerful nodes in which I am interested, but they are buried under so many redundant nodes like Twist.

In the Manipulate category, I found three powerful nodes of that kind: Point, Primitive, and VOP SOP. The Point node, as I have already described, allows mathematical transformations to be evaluated on all points. The Primitive node is similar, except it works on faces instead of points. And, last but not least, the VOP SOP. Again, not a very descriptive name nor icon, but how much raw power!

Like the Point node, the VOP SOP also applies a transformation to all points. But instead of using a hard-to-read and hard-to-write mathematical formula, you can double-click on the VOP SOP node to dive inside and manipulate a sub-network. There is a whole new world with 229 extra node types in there!

32 down, 212 to go.
Plus 229 inside the VOP SOP sub-network.
Plus 74 at the scene level, 98 at the channel level,
138 at the compositing level, 41 at the render level,
67 at the particle level, 56 at the texture level,
264 at the dynamic level...

At this rate, I don't think I will ever master all of Houdini's nodes.

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