Color of Lights / Light Render Speed Comparison

The Twilight Render Team shares tips, ideas, helpful hints, and more on using Twilight Render
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Fletch
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Color of Lights / Light Render Speed Comparison

Post by Fletch » Sat Dec 12, 2009 12:47 am

Representing the color of light correctly is very difficult, and yet very critical for realistic results.

If you are looking to solve this puzzle sooner rather than later... here are some links to review...

Color Temperature Article in Wikipedia

A Kelvin Color Chart
Image

RGB Values to 'start with' when you know your light source in Kelvin

The Light Render Speed Comparison below uses WHITE LIGHT. For more realistic render please put correct color temperature light!
This is NOT INTENDED to be the definitive answer how a light will appear, or how long it will take to render, it is only meant as a ROUGH REFERENCE GUIDE.
Individual results will vary.
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LightRenderSpeedComparison.jpg
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Zacchia
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Re: Color of Lights

Post by Zacchia » Sat Dec 12, 2009 1:50 pm

Hi Fletch
It is interesting that you post a tread about lightcolor. I was surching long time and i have a question to you: Like in your picture i found yust something about Color Temparatur. It is fine but how do i set those Color Temperatures use in a render software? I need the color in RGB for a lightsource and i do not know how i can set a Colortemparature in RGB (how to "translate") Hope you understand :lol:
Windows XP, Arcon VA HausDesigner Professional, SketchUp Pro, CasCADos 2.0.551, TheaRender, TwilightRender

Zacchia
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Re: Color of Lights

Post by Zacchia » Sat Dec 12, 2009 1:53 pm

Just seen now your link:

http://planetpixelemporium.com/tutorialpages/light.html

This allready was what i was surching for!
Windows XP, Arcon VA HausDesigner Professional, SketchUp Pro, CasCADos 2.0.551, TheaRender, TwilightRender

Tosiharu Kimura
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Re: Color of Lights

Post by Tosiharu Kimura » Sat Dec 12, 2009 3:11 pm

There is an Excel tool which changes a color temperature into RGB.
Although it is Japanese and becomes empty. ;)
If a value is put into T, it will change into a RGB value.

http://dl.dropbox.com/u/577270/K2RGB.xls

Ecuadorian
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Re: Color of Lights

Post by Ecuadorian » Sat Dec 12, 2009 7:35 pm

Most interesting, Tosiharu. I had always assumed that 6500k = RGB 100,100,100. I guess this is only true if your display device (monitor, projector) is calibrated for watching movies. :)

Fletch
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Re: Color of Lights

Post by Fletch » Sun Dec 13, 2009 12:08 am

Zacchia,
glad you read the posted links further. :lol:

to explain to others perhaps in a "layman's" terms:

If you know your light source, you start from there....
"I know I'm rendering a desk lamp... It's got a common household tungsten incandescent bulb that's 60w"
ok...
so according to the chart:
Image we can see that the color in Kelvin is somewhere between 2500k-2900k.
so from the link above: RGB Values to 'start with' when you know your light source in Kelvin we can find the RGB equivalent to be about [255, 214, 170]
or opening the color chart shown above and sampling the color for that bulb in a photo editor, you can see the RGB value for it. This is only an estimate, and may require further tweaking to please your eye, but it's a good start. Remember that every monitor, and every printer will display that same RGB color a bit differently, so really unless you are calibrated well between your monitor and printer, and you have a very high-end monitor, the color will not be displaying to you "perfectly" no matter what you do.

Thanks to Tosiharu who is providing another way of getting this information. :^:

Now that you know the RGB approximation for your light's color, use that for the RGB value in your Twilight Light Component. (pg 24, Twilight User Manual v1.1)
type it on the line like this:

Code: Select all

rgb(255, 214, 170)
That said, after experimentation with some lighting components in Twilight on my monitor, a color of

Code: Select all

rgb(230, 225, 204)
appears to give a pleasing warm incandescent-like result yet is unobtrusive. I am not, however, looking for it to accurately reflect the color of a particular degree Kelvin... I'm just looking for it to look good in a majority of situations.

pafpro
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Re: Color of Lights / Light Render Speed Comparison

Post by pafpro » Thu Mar 25, 2010 4:15 pm

conversion kelvin in RGB and more.
http://www.joviancolorpicker.com/Downloads.aspx
u can make only 10 picks color but after u can use this exe
http://pourpre.com/colorbox/index.php

Fletch
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Re: Color of Lights / Light Render Speed Comparison

Post by Fletch » Tue Apr 05, 2011 3:53 pm


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