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Wavelength to RGB


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#1 DeltaVee   Members   -  Reputation: 138

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Posted 09 October 2001 - 06:28 AM

Does anyone here know how to convert a visible spectrum wavelength to a corresponding RGB value? I know that 700nm is red(ish) in color but I would like to have an RGB value. FYI. I have a catalog of over 110000 stars, and I am trying to create a realistic sky dome texture. Thanks in advance D.V.

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#2 ragonastick   Members   -  Reputation: 134

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Posted 09 October 2001 - 11:26 PM

Well, remember that the wavelength will only tell you the hue, not the intensity or saturation unless I''m horribly mistaken. In which case, I would investigate the HSB to RGB algorithms and check out how the Hue component affects the RGB colour. I''m sure HSB->RGB help will be more readily available. Although I''m not sure whether the Hue scale corresponds to the wavelength of a colour, in which case, I''m sorry

Trying is the first step towards failure.

#3 Shannon Barber   Moderators   -  Reputation: 1362

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Posted 10 October 2001 - 07:45 PM

I''m certain that the set of wavelengths do correlate to the HSB - and equally certain it''s not a linear mapping and a far cry from 1-to-1.

I think it''d require a table of experimentally and qualitatively determined values. Or you can look at a wavelength color chart and make some @$#$ up. Stars are so small to the eye that you can just set the brightness high and give them a little bit of a hue and call it good enough. Or is this an astronomy project?



Magmai Kai Holmlor
- Not For Rent

#4 grhodes_at_work   Moderators   -  Reputation: 1361

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Posted 11 October 2001 - 03:47 AM

Here''s a clever link for you! (There''s C code!)

http://www.fourmilab.ch/documents/specrend/

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.

#5 DeltaVee   Members   -  Reputation: 138

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Posted 11 October 2001 - 03:53 AM

GDNet never ceases to amaze me.

Thanks. This is exactly the information I was looking for. I *was* looking for some ballpark estimate, but you guys came up trumps!

Thanks again.



D.V.

#6 grhodes_at_work   Moderators   -  Reputation: 1361

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Posted 11 October 2001 - 04:41 AM

Speaking of sky/space textures, are you aware of the SGI digital galaxy at the new Hayden planetarium? I''ve seen the software running at the SIGGRAPH conference in 2000. Just amazing to see this in real-time 3D.

http://www.sgi.com/features/2000/jan/haydn/
http://www.sgi.com/features/2000/jan/haydn/images/lg_galaxy.jpg
http://www.sgi.com/features/2000/jan/haydn/images/lg_mars.jpg
http://www.amnh.org/rose/digitaldome.html

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.

#7 DeltaVee   Members   -  Reputation: 138

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Posted 11 October 2001 - 04:57 AM

Never been but I would like to go one day. I''ll wait until my son is old enough.

BTW check this out:
http://space.jpl.nasa.gov/

The accuracy is astounding, they have a couple of generated images based on the time and location of real images taken from voyager, and they are nearly identical.



D.V.

#8 grhodes_at_work   Moderators   -  Reputation: 1361

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Posted 11 October 2001 - 10:29 AM

Whoa. That''s cool.

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.

#9 Shannon Barber   Moderators   -  Reputation: 1362

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Posted 11 October 2001 - 05:31 PM

Since when does Mars have rings?

#10 DeltaVee   Members   -  Reputation: 138

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Posted 12 October 2001 - 02:32 AM

I think that is saturn.

try this:

http://mars.jpl.nasa.gov/mgs/realtime/mgsrt.html




D.V.




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