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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 ...

Thank you Jose!
Great test and informative presentation.

very nice stuff


for me this thead must be place in tutorial section

thank for test

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..?

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

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

Jose,

thank you for the tutorial, it is very helpful.

jomaga wrote: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.

Great Jose...thanx for posting this.

cy,
Andronikos

This is great tip. thx!

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

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

congratulations jose!!!!

mane162

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...?

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%....