[jomaga]

definition of reflectance:
Reflectance is defined as the ratio of incident flux on a sample surface to reflected flux from the surface as shown in Figure 18.1. Reflectance ranges from 0 to 1. Reflectance was originally defined as a ratio of incident flux of white light to reflected flux in a hemisphere direction. Equipment to measure reflectance are called spectrometers


common (measured) reflectances in real world:



White (very white) glossy paper : Reflectance 88% --> 224,224,224 RGB
White mate paint : Reflectance 81% --> 206,206,206 RGB

You should´nt rise this 224 reflectance, very few materials have higher reflectances in real world.
Reflectances avobe this number increase rendering time and produce results far from reality.
It´s very important to set reflectance under 224 (88%)

Setting 100% reflectance materials (pure white materials) increase rendering time 3,5X (in this test)

This is an interor test, i want to do an exterior one soon ...

[tom]

Thank you Jose!
Great test and informative presentation.

[Maya69]

very nice stuff


for me this thead must be place in tutorial section

thank for test

[Hervé]

thanks for the test... !!

May I ask you where is the reflectance in LW...? what do you mean by setting high numbers... I just don't get it...

do U mean the color... or the reflection channel for the diffuse material..?

[tom]

Herve, it means the percentage of brightness of diffuse color while the reflection is maximum.

[jomaga]

There´s only one way to set the reflectance: in diffuse materials it´s a percentage of the meterial color.
80% Reflectance = 80% of 255 grey scale = 255 x 80 /100 = 204

High reflectance numbers = 88% = 224,224,224 grey

[Micha]

Jose,

thank you for the tutorial, it is very helpful.

[tom]

There´s only one way to set the reflectance: in diffuse materials it´s a percentage of the meterial color.
80% Reflectance = 80% of 255 grey scale = 255 x 80 /100 = 204

High reflectance numbers = 88% = 224,224,224 grey

Yes and if you're working with colors other than grey, also avoid exceeding value 224 for each channel R,G and B.

[andronikos916]

Great Jose...thanx for posting this.

cy,
Andronikos

[psanitra]

This is great tip. thx!

[Hervé]

tanks for the explanation Tom & Jomaga... clear like cristal...

[Aldaryn]

well now, this is very useful. Thanks for your time!

[mane162]

congratulations jose!!!!

mane162

[Hervé]

btw, I suppose these rules just apply to colors, not color maps like a mage of wood...?

In LW, I've put a light grey (5%) in the reflection channel (I know strange) of a maxwell difuse mat., I feel that then the color absorbs the light more... so am I doing something wrong then...?

[Hervé]

here is what I mean....

both images have all the same cam settings, same phys sky & sun, no dielectrics, no emitters....

I've lost the nice sun on the wall, but as I am saying 10% was too much, maybe 3/4%....