Barn Doors (Hotspot, Falloff):
When using vray lights, I frequently want to control how much
light spills towards the edge of the area light.
Hotspot and Falloff
In 3dsmax, this is controlled by an artificial limit defined by a
hotspot distance (full light), and a falloff distance (no light at
The Brazil renderer made this even more versatile by adding a
transition curve, so you could actually control the curve of how the
illumination transitioned between these two distances.
Standard Falloff Curve...
I know that vray prefers to deal with real world features if possible,
so if a hotspot / falloff is not possible, another possibility is a set
of barn doors. While technically a different feature, it achieves a
similar effect, which is to limit the light from the edges of the light
source without changing the characteristic of the light itself. Here's
a practical example of barn doors with a diffuser:
While a barn door can be used to directly cut off the light, usually
one would use a barn door to softly remove light from a particular
side. Maybe vray could have both...
All barn doors would have a softness parameter to control how
blurry the edge would be.
- 4 square barn doors
- a circular barn door that acts a little like the
Here's a short video discussing barn doors (starts at 3:19)
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