Indirect Lighting

Indirect Lighting

Indirect Lighting refers to the IRender nXt feature of processing light reflected from mirrors and other surfaces.

This creates a realistic lighting effect which improves with each successive rendering pass. Indirect should be used with most interiors scenes to soften the lighting effects.

Incorporate the effects of reflected light, such as the reflected cove lighting above this suspended ceiling.

Indirect Lighting refers to the feature of processing light reflected from mirrors and other surfaces.

Indirect lighting, or lighting reflected from other surfaces, can add some subtlety and realism to your exterior rendering. In particular, the undersides of overhanging features such as eaves or balconies can be rendered more accurately when using indirect lighting.

This subtlety, however, comes at a performance cost. More passes will be required to resolve the image, and each pass will take longer.

  • More realistic lighting effects.
  • Subtle, soft shadows due to reflected lights.
  • Better images for presentations.


Cove Lights

Indirect lighting from lights above suspended ceiling.

In this example, the lights are placed above the suspended ceiling and reflected into the room from the main ceiling.

The lighting becomes smoother and smoother as more bounces are processed during each rendering pass.



There are two methods for Indirect Lighting - Standard and Gather.

Gather sometimes produces a smoother effect, but takes longer.

Gather Indirect Light uses Monte Carlo like techniques to solve the indirect portion of the lighting. Images start out noisy and gradually refine. May be useful for exterior daylighting-- much slower for interiors than standard method and not much better.


The default for indirect lighting bounces is 1, meaning that a light shining on a wall or mirror, will be bounced once, but it is not, then, bounced off of additional walls.

You can increase this value for special situations, but each bounce added will add to the rendering time.

Other Examples

This is a SketchUp model of a room with a spotlight shining on the far wall. The partition in the middle of the room prevents direct light from the spot light from reaching the right hand wall.
Rendering with direct light only. All ambient light is turned off to highlight the effect of the single spot light.

Rendering with just 3 lighting passes. This starts to show the effect of indirect lighting, but still has harsh shadows.
Rendering after 20 lighting passes. Light is starting to blend and create realistic lighting.

Rendering after 20 lighting passes. Rendering is fairly smooth.

See also