What does "Correction for lumen units" mean?
When Use Inverse Squared Falloff is turned on, Intensity of point/spot light seems to be internally multiplied by 16.0.
What is the meaning of this 16.0f ?
This value results in white diffuse material lit by 1963 lm point light with distance of 100 cm returns color 1.0.
In other words, white diffuse material lit by 156 lx returns color 1.0.
Is this a magic number without any physical meaning? If so, why this value is chosen?
asked Oct 29 '15 at 11:12 AM in Rendering
f at the end means number type is "float", not "double" which is default fraction number type when you use ".x" (x being faction number) at the end
Other then that i guess it's to correct units used in rendering libraries to be closer in resemblance of real world unit of lumen
answered Oct 29 '15 at 05:05 PM
I know this is a somewhat old thread, but I would like to inform you about the rationale behind this x16 factor, as I just got a reply from Epic on this regard.
Basically, it is a compensation factor to make things look bright enough at default exposure settings.
For the interested reader, this is the question: https://udn.unrealengine.com/questions/280050/clearing-confusion-with-photometric-measurements.html
answered Mar 11 '16 at 01:21 AM
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