November 1, 2006
By Mike Hudspeth
What do you do when you have a design project that absolutely must have free-form surfaces? Everyone has a project like that eventually. Consumer products are notorious for them. But there are all sorts of other, less-obvious products that you just can’t design well without those wonderfully hard-to-define surfaces. What do you use? Well, in the old days you called a sculptor and created a mockup model. Sometimes it was made of wood, sometimes foam. Clay was also popular for molding shapes. But however you made it, it was always hard to detail in a drawing.
Eventually, along came Alias surface modeling software. You could model just about anything you wanted, but sometimes getting that surface was the very definition of tedious. And it came at a price.
> > Figure 1: User-definable points allows locking down shapes of variable radius blends like never before.
Nowadays, however, there are options that let the creative juices flow and won’t break the bank. Robert McNeel & Associates started out as an AutoCAD reseller and design firm. Over the years the company got a lot of requests for additional functionality that AutoCAD just couldn’t handle. The experts began to write macros, then add-ins. Soon, they had come up with a truly phenomenal product: Rhinoceros.
Setting You Free
Rhino 4, the latest incarnation, is a free-form design package par excellence, in use by a large, loyal user base. Rhino can help you create just about any shape that you can imagine fairly easily and quickly. Not only that, but Rhino 4 can be, and is, used for other things as well.
< < Figure 2: When you add a surface to blend two others, Rhino 4 makes the curvature flow continuously. Likewise, if you need to change the blend surface, Rhino 4 will keep the surfaces continuously blended.
Because Rhino 4 can import such a wide range of file formats, people sometimes use it simply for file translation. You can import or build something and pass it on to other mechanical programs. Rhino 4 is compatible with most any kind of 3D modeling format you can imagine, including such formats as IGES, DXF, Unigraphics NX, CATIA, Pro/Engineer, plus a whole host of others.
Sometimes models come through a translation with flaws because of tolerance differences between software packages. Rhino 4, with some pretty powerful healing capabilities, enables you to repair them. Because meshes in Rhino are treated like NURBS, anything you import into Rhino 4 is treated as native data. You can do anything you want to it. Talk about flexibility.
> > Figure 3: Universal Deformation Technology (UDT) features let you drastically reshape your model.
Rhino’s real strength comes in its high-end surfaces and solids creation and manipulation. That’s right, Rhino 4 works with solids, something Alias doesn’t. Let me clarify: Rhino 4 works with poly-surfaces. Poly-surfaces are technically solids, but don’t have to fully enclose a volume. You can have an open-ended box and Rhino 4 will recognize it as a solid. Rhino is not a parametric modeler, but don’t hold that against it. It can do some remarkable things. There is a history in Rhino 4 of what you’ve done and the order in which you created it, but it can be broken when necessary. In previous versions, surfaces were separate from their creation curves. If you needed to make a change after creation, you had to delete the surface and recreate it. Now the surfaces remain associative to the creation geometry.
One of the nicer options in Rhino 4 is the variable radius blend. Rhino 4 gives you nice handles and points (see Figure 1, above) so you can control the blend easier. The downside is you can’t edit the blends once they are there. You just delete them and start again. When you blend surfaces, Rhino 4 gives you Bezier handles and lets you add new shapes (see Figure 2, above). When editing your surfaces you grab hold and move them around, but Rhino 4 will maintain the end conditions. What is born continuous curvature will remain that way until you instruct it otherwise.
< < Figure 4: SPLOP lets you build your model flat and apply it like a sticker to another surface. As a result, it takes on the contours of the target surface.
Pulling the Strings
Universal Deformation Technology (UDT) stretches, pulls, and twists your models (see Figure 3, above). SPLOP (see Figure 4, above) and SPORPH (see Figure 5, below) let you build an entire component on a flat plane and then orient it on a surface. SPLOP positions your component on a target surface at a specified point. SPORPH (spatial morphing) does basically the same thing but will scale the component to cover the entire surface. Flow Along Surface lets you do somewhat the same thing, but in this case you can associate your flat, controllable model to a curve (see Figure 6, below). The Cage command is like Envelope in CorelDRAW. It lets you make wholesale changes to your model without associating it to anything. It defines the space of the model and gives you handles to manipulate it.
> > Figure 5: SPORPH (where do they get these names?) lets you control your model by letting you wrap it across a controlling surface. It will scale it to fit the entire surface.
In a lot of 3D modelers you work with your geometry is colored by default values that are anything but realistic. Rhino 4 is different. The marvelous real-time rendering with texture maps lets you see what your model is going to look like, and you can rotate it!
Rhino 4 has a few other handy features well worth mentioning. They’ve added some new drafting capability. It’s not meant to be a full-on drafting package, but it will give you enough capability to get the job done. Rhino 4 has all kinds of plug-ins available for building everything from shoes to boats. For instance, RhinoART is for modeling artistic shapes from raster images. It can create 3D relief from image files, reliefs using colors or curves, 2D curve geometry from image files, puffed up volumes using closed curves, and sweep volumes using various profiles. RhinoCAM can create toolpaths right from within Rhino 4. Flamingo, Rhino’s high-end renderer, can turn your models into photorealistic images people will swear are photos of actual products. Bongo handles animations for Rhino 4. With it you can bring your models to life.
< < Figure 6: You can model your component flat for tight control and then associate it to a curve that you can manipulate to your heart’s content.
One of the nicest features of Rhino 4 is its pricing: $895 for a seat, Flamingo costs $495, and Bongo is $495. Educational pricing is also available.
> > Figure 7: Rhino 4 has high-quality real-time rendering. It’s pretty great to work with the materials and textures you will make the product from.
Obviously there is much more in Rhino 4 than can be covered in such a small space. If you need to assure your designs look great, Rhino 4 is definitely worth a close look. You can find more information about Rhino 4 and its plug-ins on the website. Check them out. You’ll be glad you did.
Mike Hudspeth is a senior designer for Tyco Healthcare, and has been using a wide range of CAD products for 20 years. Send your comments about this article through e-mail by clicking
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McNeel & Associates, Inc.