Levels of Optimization

There are three Levels of Optimization to choose from for each of the above optimization types:

Minimal: This mode is best used for very simple scenes with less than five objects. In this mode, Bryce predetermines the areas where your objects reside and shoots rays only through that area.
Normal: This is the best mode for most scenes. In this mode, Bryce determines where your objects reside and then examines the concentration of objects within the larger area. This eliminates the computation of unnecessary rays.
Aggressive: This is a more extreme version of Minimal mode. It is best used for complex scenes with localized concentrations of objects. If you have imported DXF objects in your scene, this mode will speed up rendering considerably.

To set Optimization Options:

Either click the triangle icon next to the Render Controls, choose Optimization from the menu, then the optimization type and level.

or
Click the triangle beside the Render Controls and click Render Options.
Choose an optimization type and level from the Render Options dialog.
Click on OK to close the dialog.