With such heavy demands, an older or slower system will have a hard time keeping up with your commands, creating jerky animations and temporary pauses. In real-time ray-traced mode, whenever you make a change to your CAD model, your system must recalculate on the fly the interplays of lights, shadows and physics to re-render your on-screen view, down to the smallest details. You’ll notice a lag, for instance, in model rotation and geometry rebuild after an edit. The price you pay to be able to view your assembly in that mode is slower system response. Projecting shaded volumes, casting realistic shadows and showing reflections on surfaces consume a tremendous amount of computing power. No doubt you’ve heard the saying “the devil is in the details.” In CAD, with every detail you turn on, the devil exacts a tax in performance. With real-time ray-tracing, the term “photorealism” takes on new meanings, as the process uses complex algorithms to calculate light bounces to project shadows and reflections in a way that’s consistent with how they would appear in the real world. In a few CAD programs, you can turn on real-time ray-tracing in your interactive modeling window. As you turn on other details-such as hidden lines, shading, ground plain shadows, and reflections-the assembly in your modeling window begins to acquire more realism. This Spartan option shows you the curvatures and edges of your design-and nothing else. The simplest option provides you with basic geometric volumes and outlines. When working in a CAD program’s modeling window, you usually have several display options.

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