开发快报－规则的力量

By Wolfgang Seibold, Senior Software Engineer

LAWs allow developers to adapt individual APIs to their specific needs or define their behavior. In surfacing for example, LAWs can be used for precise control over the surface generated. Warping supplies an interface which allows the user to define their own space deformations which get applied to a body.

ACIS LAWs are versatile and capable of many different functions. A LAW can control the tangency of skin operations, the draft angle and/or twists of sweeps or define the 3D deformation for warping. Ultimately a LAW is defining a mapping from one space to another. The spaces do not require the same dimension as in the skin example where we are mapping from a t value on a curve (1D) to a vector field (3D).

There are two ways to use LAWs. The first is to use the ACIS set of predefined LAWs and concatenate them to build more complex ones. The other option is to derive your own LAW. Using the ACIS LAWs is ideal for prototyping to accomplish something quick. Although for production code we recommend deriving your own LAWs to ensure better performance.

The following examples give you a small sampling of the power of LAWs.

The first example illustrates a vector law mapping from 1D to 3D. The first image shows the result of the standard sweep, whereas the second image illustrates the sweep with a user defined rail LAW affectively stopping the profile from twisting around the path (the vector field is added for demonstration purposes).

In the second example a LAW is used to make the hyperbolical sin wave surface sin(u*v/5). u and v are parametric coordinates defining a mapping from 2D to 3D.

The remaining examples illustrate LAWs which are defined from 3D to 3D showing off different space warps. The first one takes a shoe model (courteously provided by Cimatron Ltd) and produces a "wide" version of it. We are attempting to keep the heel fairly unchanged and generate a wider toe box by using a tapered stretch along one axis. The figures show the model before and after the operation. Click here for an interactive 3D model

Before	After

In the next model I wanted to add an arch support. In order to achieve this I derived my own LAW which deforms the space around a “hot spot” producing a bump in the model.

Before	After

In the final model I did a series of deformations similar to the previous example. I started with a sphere, adding six deformations and a couple of Booleans to end up with my free form gremlin. I wanted to illustrate that deformed bodies/surfaces in ACIS behave just like any others and therefore standard modeling operations can be applied. Click here for an interactive 3D model

Images courtesy of Cimatron