Download Video - 30MB [6 Min.] It is time to get the Apprentice Blog back up and running. Originally started to introduce Houdini 9 to the community, there have not been very many follow up lessons. There are lots of interesting topics to discuss when it comes to learning Houdini and this is a great place to share new ideas. In this entry, you will learn how to model a soccer ball (or should I say...football). Houdini's platonic solid tool actually comes with a soccer ball topology but it looks more like a dungeons and dragons die and less like a proper piece of sports equipment. To create a ball that is spherical and has the grooves modeled properly, a couple off different techniques are used. First, the platonic solid is subdivided which makes it roundish. But because of the different shapes in the patches, the surface is uneven and not spherical. A primitive sphere is then used along with the ray surface operator to project that uneven topology out to create a spherical shape. 
Now because the platonic solid was subdivided, the original patches are now made up of many faces. To isolate the patches to perform a polyextrude that will create the ball's grooves, the primitive numbers from the original shape are assigned to the model as a primitive attribute. After the model is subdivided, these attributes stay with the new faces making it easier to identify the patches. The foreach sop then uses this attribute to isolate the patches and by diving inside the foreach node you can polyextrude out the patch. This operation is then applied to all off the patches and you have your soccer ball shape. The patches are then fused back together and another subdivision shows a nice rounded ball.The parameters inside the foreach sop can then be tweaked to get the look you want.  This is a very Houdini-centric modeling exercise which shows in a simple example how several different techniques can be combined to get the shape you need. There is a growing interest in modeling in Houdini and future blog entries will continue to look at this important topic. Addendum It was quickly pointed out to me that the "Soccer Ball" shape in Houdini's platonic solid tool is actually a Truncated rhombic triacontahedron while a real soccer ball shape is actually a Truncated icosahedron or "Bucky Ball" (Learn more here). Therefore my image will feel wrong for all the real football fans;-)  To get a real football/soccer ball, you can apply same steps to the following bucky ball geometry instead of the platonic solid that comes with Houdini: Download Buckyball Geometry - 2K] Thank goodness that Houdini's node-based workflow lets me insert the bucky ball geometry into my existing network and the whole system works without having to redo the modeling steps. Another reminder why Houdini's procedural approach can make a difference for modelers. On your own... Jeff Wagner [Old School Blog] pointed out to me that another thing worth exploring is the sphere that is used to ray the buckyball shape after it is subdivided. Instead of a sphere try a box or an american football shape and see what happens. Here are a couple examples. In these cases I increased the subdivisions on the buckyball just before it was rayed out to get more detail. The key is that I was able to make these changes by modifying my existing soccerball network and didn't have to start from scratch each time - the advantage of going procedural. 
Robert Magee User Comments
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