Rendering Solid-Transparent Appearances

You can use Refract Background to obtain more plausible results when you render scenes that use a solid-transparent appearance and have a backplate or background color.

Refract Background is a project property. If you turn it on or off, the change applies only to the active project.

Typically, the refractive rays in a scene are computed from the HDR environment, whether it is visible or not. However, if the HDR environment is hidden by a backplate or background color, problems can occur when you render objects with solid-transparent appearances.

For example, this scene shows a glass with a solid-transparent appearance. Because the HDR environment is visible, the background and lighting come from the same source. The transparency is plausible.

If you render the same scene with a backplate or a background color, the HDR environment is not visible. If Refract Background is off, the transparency effect is broken because the color from the invisible HDR environment still passes through the transparent glass.

Backplate Refract Background off	Background color Refract Background off

If Refract Background is on, the software computes the refractive rays from the backplate or the background color. The reflections and illumination are derived from the HDR environment. The results are much more plausible.

Backplate Refract Background on	Background color Refract Background on

To turn Refract Background on or off:

1. In the Palette, on the Scenes tab, select an environment in the tree.
2. On the General subtab, select or clear Refract Background.
   • If selected (on), the software computes the refractive rays from the backplate or the background color.
   • If cleared (off), the software computes the refractive rays from the HDR environment.
   The state of the Refract Background property is changed only within the active project.

   Refract Background has no effect if the HDR environment is visible.