Brian’s 3D ABCs: Scaling ACIS Objects

Simple scaling in TurboCAD is generally accomplished by selecting the object and then setting the x, y, z scale or size for that object. However, ACIS objects do not always scale that easily.

Within the framework of TurboCAD there are basically two categories of ACIS Objects: typed and un-typed, and they can scale a bit differently. Examples of typed objects are those labeled spheres, extrudes, cylinders and boxes Un-typed objects are just labeled as “ACIS Solid”. To see how an object is labeled you can just select that object and then look in the top half of the Selection Info palette. There is a third category, Parts. Parts are top objects in the Part Tree and only occur when the Part Tree is active. There is a lot to say about the Part Tree and we’ll be addressing it in a future blog post. For now let’s just concentrate on the first two categories.

Typed objects are just the objects that result from using the basic 3D Object tools. Un-typed objects result when you explode a typed object, or when you apply a Boolean, Slice or Quick Pull operation on a Typed or Un-typed object. (unless the Part Tree is on).

Un-typed objects are simple. You can scale them along any axis all day long with no problems.

Typed objects are parametric, and will respect a simple scale operation in any direction which wil allow the object to retain its relationship to its parameters. For example, you can scale a Box in along any or all of the three axes with no problem. Since a box’s parameters are height, length, width, the parameter is simply updated. However, a sphere has a single parameter, Radius. If you attempt to scale along just one or two of the axes the scaling operation will be rejected, or fail. This is because the result would be an ellipsoid with different radii along each axis. You can scale a sphere if you scale along all three axes proportionally.

Here are a few other limitations:

• Hemispheres are limited just like spheres.
• Extrudes cannot be scaled along the length of extrusion.
• Torii can on be scaled along their Z axis freely, but any attempt to scale along x or y will cause the scle to be changed for both x and y.

If you cannot get an ACIS object to scale the way you want chances are it is Typed! Just explode it (or a copy of it) and proceed to scale.

Happy Scaling!