[tom]

Back to subject, what makes a pink glass may have more than one reason.

1) Same pink transmittance with attenuation equals to 2 times of its thickness.
2) A red transmittance with more attenutation.
3) A light pink transmittance with less attenuation.
4) Endless possibilities of 2 and 3

Since all of these are producing the same pink for the same thickness, they are all the same material, I hope I could explain.

[jonathan löwe]

thanks for explanations...seems more understandable now!!!!

jona

[raffaello]

Thanks !! this is very nice..

P.S. do whe take, after this, some kind of diploma?. or a bachelor in phisics ?..

[tom]

..hehe c'mon you are already achieving 100x harder things.

[Thomas An.]

Every substance has a complex index of refaction M.
'Complex' means that there is a numeric part and an 'imaginary' part (M = N + i*K ... where 'i' is the square route of -1; thus iK is the imaginary component).

In case of dielectric substances the "K" coeficient is neglidgeable and drops out leaving us with M=N.

The coefficient N is different at specific wavelengths (light bends differently depending on color). Since it is impractical to always consider all wavelengths we end up using the refraction index of the yellow spectra (at about 570nm). The yellow index of refaction is the known Nd value (sodium yellow).

Each substance (opeque or not) has measured N and K values.
http://www.luxpop.com/

So for example Silver (Ag) has N=0.12 and k=3.5 at 570nm
http://www.luxpop.com/cgi-bin/calc_2005_12_01.cgi

I am not sure how Maxwell corrolates these coefficients into its own 1-20 ND range (or if it using a different model of thought)

Maybe for best accuracy we should try to locate a material from the Maxwell complex IOR list that best matches our application (instead of trying to come up with our own).

[tom]

Nd for Maxwell = K @ 570 nm

[Thomas An.]

Nd for Maxwell = K @ 570 nm

Thank you Tom.

You mean Nd for opeque substances in Maxwell = K. Right ? (because dielectrics do not have a K aspect).

I suspect since most (if not all) dielectrics have refraction coeficient Nd =< 3, then Maxwell automatically switches to "k" if we input Nd >= 3.

Also it seems like Aluminum (which is used for mirror coating) has a k=5.59 ... So, I it doesn't seem to get much higher than 6 (not sure if k=20 or k=100 exists)

[tom]

There's no such border like 3, it's what we suggest for common usage, it has no meaning. For opaque or transmissive substances, Nd is Index of Refraction at sodium line. Like you've said, even most refractive transmissives have Nd<3, so the remaining part (Nd>3) can be treated as opaque susbtances. I'm not sure if 20 or 100 exists too but this doesn't mean they are producing non-physical results. We just wanted to keep the range high instead of limiting it to the existing materials in the nature.

[jomaga]

Btw, some IOR (Nd) known data:

Minerals & Gemstones

Alexandrite 1.746 - 1.755
Almandine 1.75 - 1.83
Amber 1.539 - 1.545
Amethyst 1.532 - 1.554
Ammolite 1.52 -1.68
Andalusite 1.629 - 1.650
Apatite 1.632 - 1.42
Aquamarine 1.567-1.590
Axenite 1.674 - 1.704
Beryl 1.57 - 1.60
Beryl, Red 1.570 - 1.598
Chalcedony 1.544 - 1.553
Chrome Tourmaline, 1.61 - 1.64
Citrine 1.532 - 1.554
Clinohumite 1.625 - 1.675
Coral 1.486 - 1.658
Crystal 2.000
Crysoberyl, Catseye 1.746 - 1.755
Danburite 1.627 - 1.641
Diamond 2.417
Emerald 1.560 - 1.605
Emerald Catseye 1.560 - 1.605
Flourite 1.434
Garnet, Andradite 1.88 - 1.94
Garnet, Demantiod 1.880 - 1.9
Garnet, Mandarin 1.790 - 1.8
Garnet, Pyrope 1.73 - 1.76
Garnet, Rhodolite 1.740 - 1.770
Garnet, Tsavorite 1.739 - 1.744
Garnet, Uvarovite 1.74 - 1.87
Hauyn 1.490 - 1.505
Iolite 1.522 - 1.578
Jade, Jadeite 1.64 - 1.667
Jade, Nephrite 1.600 - 1.641
Jet 1.660
Kunzite 1.660 - 1.676
Labradorite 1.560 - 1.572
Lapis Lazuli 1.50 - 1.55
Moonstone 1.518 - 1.526
Morganite 1.585 - 1.594
Obsidian 1.50
Opal, Black 1.440 - 1.460
Opal, Fire 1.430 - 1.460
Opal, White 1.440 - 1.460
Oregon Sunstone 1.560 - 1.572
Padparadja 1.760 - 1.773
Peridot 1.635 - 1.690
Quartz 1.544 - 1.553
Ruby 1.757 - 1.779
Sapphire 1.757 - 1.779
Sapphire, Star 1.760 - 1.773
Spessarite 1.79 - 1.81
Spinel 1.712 - 1.717
Spinel, Blue 1.712 - 1.747
Spinel, Red 1.708 - 1.735
Star Ruby 1.76 - 1.773
Tanzanite 1.690-1.7
Tanzanite 1.692 - 1.700
Topaz 1.607 - 1.627
Topaz, Imperial 1.605-1.640
Tourmaline 1.603 - 1.655
Tourmaline, Blue 1.61 - 1.64
Tourmaline, Catseye 1.61 - 1.64
Tourmaline, Green 1.61 - 1.64
Tourmaline, Paraiba 1.61 - 1.65
Tourmaline, Red 1.61 - 1.64
Zircon 1.777 - 1.987
Zirconia, Cubic 2.173 - 2.21

Liquids

Acetone 1.36
Alcohol, Ethyl (grain) 1.36
Alcohol, Methyl (wood) 1.329
Beer 1.345
Carbonated Beverages 1.34 - 1.356
Fruit Juice
Chlorine (liq) 1.385
Cranberry Juice (25%) 1.351
Glycerin 1.473
Honey, 13% water content 1.504
Honey, 17% water content 1.494
Honey, 21% water content 1.484
Ice 1.309
Milk 1.35
Oil, Clove 1.535
Oil, Lemon 1.481
Oil, Neroli 1.482
Oil, Orange 1.473
Oil, Safflower 1.466
Oil, vegetable (50° C) 1.47
Oil of Wintergreen 1.536
Rum, White 1.361
Shampoo 1.362
Sugar Solution 30% 1.38
Sugar Solution 80% 1.49
Turpentine 1.472
Vodka 1.363
Water (0° C) 1.33346
Water (100° C) 1.31766
Water (20° C) 1.33283
Whisky 1.356

Transparent

Eye, Aqueous humor 1.33
Eye, Cornea 1.38
Eye, Lens 1.41
Eye, Vitreous humor 1.34
Glass, Arsenic Trisulfide 2.04
Glass, Crown (common) 1.52
Glass, Flint, 29% lead 1.569
Glass, Flint, 55% lead 1.669
Glass, Flint, 71% lead 1.805
Glass, Fused Silica 1.459
Glass, Pyrex 1.474
Lucite 1.495
Nylon 1.53
Obsidian 1.50
Plastic 1.460 - 1.55
Plexiglas 1.488
Salt 1.516
Silicon 4.24

Metals

Aluminum 1.39
Copper 2.43
Gold 0.166
Mylar 1.65
Nickel 1.08
Platinum 2.33
Silver 1.35
Titanium 2.16
Steel 2.50

Misc

Helium 1.000036
Hydrogen 1.000140
Oxygen 1.000276
Argon 1.000281
Vaacum 1.00000
Air 1.0002926
Nitrogen 1.000297
Carbon Dioxide 1.000449
Liquid Hydrogen 1.0974
Liquid Nitrogen 1.2053
Chlorine 1.385
Carbon Tetrachloride 1.460
Turpentine 1.472
Plexiglass 1.50
Benzene 1.501
Sulphur 1.960

[jdp]

jomaga thank for the list but it doesn't make sense to me.
if ND is the same as IOR, so there is something wrong with material editor in maxwell... otherwise ND and IOR are completely different and those values wouldn't work as correct ND values.... I must admit that I am a bit confused now....

[lllab]

no nothing is wrong:
nd is the value for wavelenght @ ca. 550nm.

it is more or less exact but takes one value for fresnel. (glas=1.51)

IOR: takes another value for each wavelenght ( glas_ 1.51@550nm, 1,53@650nm, 1.55@1000nm etc.) so it takes the change of fresnel inrelevance of change of the wavelenght into account- so its even more accurate than N.D. but takes longer to render of course. metals have very complex IOR p.e.

lets all study physics;-)

cheers
stefan

[j-luc daureil]

In short, you will use the same IOR value you use with other applications.
And if you have further questions, please let me know.

Tom

Tom many thanks for all your explainations;

The curves above make sense for me but i don't understand the curve in the material inf section of the material editor:
these curves are "flat" even if Nd is 20 or more (for +30 there is no curve)



May i miss something here...?

And i've another question:
what is an .r2 file? I' don't found any information on the forum.

I've seen some .ior file in the maxwell directory but no .r2
I'm curious if this kind of .r2 file could solve these questions about the "good" nd numbers...

J-Luc