Syntax:

glow_opacity = <scalar>

Range:

Any non-negative number

Default:

0.0

Purpose:

To allow a shader glow to obscure objects.

Comments:

Normally the shader glow is added on top of the light in the scene. If the opacity is greater than zero, then the glow will be more opaque where it is brightest. This is useful when simulating fire and smoke effects, which frequently do not let all the light in a scene pass through. If you want the glow to appear on the background only, and not obscure any objects, then an opacity value of -1 will do this.

Example:

glow_opacity = .3