Lights and passes

As rendering passes are processed, there are two effects on Artificial Lights:

1. Only about 1/3rd of the lights are processed per pass.
2. Random points are sampled in each ligt for each pass.

In this model, the ceiling lights have a rectangular area light above a grid.

This provdes a good example of how random points in lights are sampled for each pass.

1 Pass

At the end of the first pass, only one point has been sampled from each ceiling light.

5 Passes

At the end of 5 passes, more points have been sampled from each light, but it will take more than 20 passes to make the lights complete..

20 passes

At the end of 20 passes, the lights are almost complete. However, this scene will require 100 passes or more to allow all the light sources to converge.

See the image at the top of the page for the result after 100 passes.

Blurry Reflection

Note in the ceiling light images above how the reflection of the windows in the ceiling starts out sharp in the first pass, but then gets blurry - which is the desired effect - with additional passes. This is accomplished by sampling the pixels on the reflective ceiling in slightly different directions on each pass and combining the images.

The amount of blurriness is effected by the Sharpness setting on the Material Wizard .

Similar to, and related to, the sampling of light, shadows start out harsh in the first pass and get softer and more realisti with each subsequent pass.

1 Pass

At the end of the first pass, shadows are very sharp.

They will soften with additional passes - both because more light sources are sampled, and also becuase the indirect effects of reflected lights are processed further in each pass.

20 Passes

After 20 passes the shadows get much softer and much more realistic.

After 100 passes or so, these will get much better.

See the image at the top of the page for the result after 100 passes.