Invisible

Invisible is an Object Property which makes a group, component, or face invisible when rendering with IRender .

It can be used to mark geometry which is visible in SketchUp as invisible when rendering with IRender.

Lights

One use if if you want to make a lamp or light fixture which illuminates the scene but which is not invisible.

In this example, the floor lamp is invisible, but still illuminates the rear wall.

Invisible lamp illuminates back wall.

Note: Invisible objects do cast shadows. (which makes them useful for canisters around lights which need to block the light.)

For example, here the table is invisible but still casts a shadow.

Invisible table still casts shadows.

Here is an example of using an alpha-transparent material on an invisible face to cast shadows on the scene.

Shadows from an invisible wall.