Umbra 3 culling accuracy, query time and memory usage are mostly dictated by the chosen set of computation parameters – in addition to the scene geometry. Most of the parameters correspond to the unit scale of the scene’s geometry and the below table presents good starting values for inches, feet, meters and centimeters.
When you first load a scene in the Umbra Debugger, you have to choose what the unit scale of your scene is from the World Properties pop-up dialog.
From the Unit scale, Umbra Debugger can automatically recommend good default parameters. You can change these parameters from the sliders or text input boxes in the "Computation" tab.