Negative luminosity

[Volker Harun]

Hi,

pfrancke made a nice story to a nice image here.
He did a bit of misunderstanding my hint to negative luminosity.
Of course it is adding more interesting shadows, but I never used a lightsource for this, this is the idea of ... in this thread .... (will be completed, as soon as I have the information)

I use the negative luminosity within surface layers. Say you have gray sphere and you go the luminosity tab, activate it and give it a value -0.4. Choose a bright, saturated colour and watch the preview.

In the attached image you see two spheres, the closer one uses negative luminosity, the other one, it uses the 'negative luminosity-colours' as normal colours without any luminosity.

Of course, I use it more subtle than in this scene. It is very effective when using the displacement-function as function for the luminosity, too ... more effective, using reflective surfaces. See the second image.

Volker

[Henry Blewer]

Sorry, I don't follow the 'negative luminosity-colours'. How can a surface which has no luminous property have 'negative luminosity-colours'? You have made me intensely curious.

[pfrancke]

OMG  that is a nice effect.

[Volker Harun]

njeneb ,

if you have white light shining on an object ... this object absorbs light, light of a specific wavelength. Light of other wavelength gets reflected, which is our subjective perception of colour.
This works as long as the amount of negative luminosity is weak.

So a grey 'coloured' sphere with a blue as negative luminosity turns to be orange. A green sphere with a blue negative luminosity gets shades of brown and so on.

Volker

[Volker Harun]

Not to confuse anybody, I do not use the luminosity of the 'Default shader' ... I use the 'Surface layer' 

[Henry Blewer]

I see, in the real world, you would be using the light absorption factor to derive color. Almost a spectrum effect.

[Cyber-Angel]

Color is a function of wavelength the sum of all wavelengths (See visible Spectrum: http://en.wikipedia.org/wiki/Visible_spectrum) of light is white light or daylight, for example blue light is a shorter wavelength than red. The amount of reflection of a surface is called its Albedo http://en.wikipedia.org/wiki/Albedo.

Regards to you.

Cyber-Angel 

[rcallicotte]

Maybe I would need to try this out, before I understand it.  I understand the concept, but the idea of "...the other one, it uses the 'negative-luminosity-colors' as normal colors without any luminosity.' is not clear.  I understand when you use negative luminosity that it has an affect as you described, but what is the second (quoted) explanation about? 

[Henry Blewer]

It is something I really need to use, experiment, and see to understand.

[mhaze]

Nice
Just tried playing with this, gives some interesting effects