#Luminance and Wattage
5 messages in this thread
Dear Greg,
I've been teaching a lot of architectural 3DS classes lately and I get this
question all the time:
Is it possible to somehow connect omni or spotlight luminance with wattage?
I've been saying no, citing all the other factors that come into play in real
life: radiosity, shadows etc. However there are a few other packages that have
wattage settings. I think Accurender is one.
It seems to me that wattage settings in non-ray-tracing packages wouldn't be
perfectly accurate anyway. If all we're working with is an approximation, then
is there one in 3DS?
Thanks
Michele
Wattage would not be accurate regardless what you use (raytrace or scanline
render). Wattage is a function of energy spent not amount of light produced.
Different sources of light consume different amounts of energy even if
providing the same amount of light. Maybe lumens would be an alternative or add
the sophistication of specifying the light source type along with the Wattage
(Halogen, simple incandescent, fluorescent, sodium gas, etc.)
the geek…
In addition to Gus's comments, light dissapates as an iverse proportion to
distance, IOW non-linearly. However, most apps (excepting some ray-tracers)
calculate light dissapation linearly for both ease of adjustment and render
speed. Soooo, even if you knew the lumen power of a light source, the
dissapation would be wrong.
If you really need to make it happen, you could do some rea- world tests with a
light meter, a camera, and a calibrated scanner to create a table of lumens
corresponding to pixel luminance. But even that has limitations on a single
light source that affects two objects at different distances.
— James — Choreo Motion —
Michele, PMJI, but you posed a great question and I had to answer too. I
recently finished work for a lighting manufacturer who wanted to show their
lights in different settings yet the product was not yet finished. Much of it
was still images used for a print piece, but it was cool work. They had
specific bulbs and wattage requirements also, but what it really came down to
was just making it look great. They knew how a 50 watt metal-halide bulb
illuminated a corridor, and they had photometric's to go from also. That, in
turn with just them sitting down with me, was all I needed. I think if you set
up some simple tests and did a little research it would be relatively easy to
write a keyscript program to convert wattage into a 3DS lumiinance value.
Though radiosity etc. would still have to be simulated. Good idea…
DM
Michele:
>> omni or spotlight luminance with wattage?
In addition to the words of wisdom from others here, may I add mine: Fake It!
Greg Pyros :^)