absorption and scattering coefficients for liquids

Kram1032 · Post by **Kram1032** » Tue Aug 21, 2007 2:49 am

then, increase the concentration^^ - I posted datas, about what tsp tbsp and cup are

looks very good now.

milk is the white one in the front, right?
I think, it looks kinda too solid, for some reason...

CoolColJ · Post by **CoolColJ** » Tue Aug 21, 2007 9:48 am

looks like it should now

deltaepsylon · Post by **deltaepsylon** » Tue Aug 21, 2007 10:36 am

agreed

the reason the milk looks weird prob. is that there is no cup, and milk looks like a 'hard' liquid

Kram1032 · Post by **Kram1032** » Tue Aug 21, 2007 10:43 am

milk in a glass still looks different...

mrCarnivore · Post by **mrCarnivore** » Tue Aug 21, 2007 7:24 pm

ass liquids look good as far as I can tell - except milk and chocolate milk.

the milk looks like paint (too much sss) and the chocolate milk doesn't look chocolaty (is that a word?) enough. You should reduce sss and either change sss colour or increase absorbtion.

The rest looks good.

Kram1032 · Post by **Kram1032** » Wed Aug 22, 2007 2:54 am

yeah, that's it!
That's what I meant - milk looks like paint

CoolColJ · Post by **CoolColJ** » Mon Sep 03, 2007 11:51 pm

this pic is by Henrik Wann Jenson. I spoke with him a while back, and begged him to release his Dali renderer

This image shows how milk can be rendered realistically using the BSSRDF model. From left to right we see skim milk, whole milk, and diffuse milk. The diffuse milk has been rendered using a traditional BRDF model, which results in a hard appearance making the milk look more like white paint rather than milk. The difference is even more noticable once the light moves - this can be seen in the animation "Rendering Translucent Materials" on the animations webpage.

animation is freaky!

large
http://graphics.ucsd.edu/~henrik/animat ... ET2001.avi

small
http://graphics.ucsd.edu/~henrik/animat ... -small.avi

Kram1032 · Post by **Kram1032** » Tue Sep 04, 2007 2:24 am

looks great

I wouldn't want to drink that diffuse milk xD - I prefer the whole milk: looks the healthiest, not as pale and translucent as the skim milk.

SURFiNG · Post by **SURFiNG** » Wed Sep 05, 2007 11:45 am

milk seems to look quite ok with indigo 0.8 stable and MLT (not BiDir)
(sorry for bad colors, i've tonemapped it due 1 hour render only!)

CoolColJ · Post by **CoolColJ** » Wed Sep 19, 2007 2:30 pm

interesting - Whaat's milk values also goes blue in colour, just like mine. I suspected it maybe due to the sun. So I rendered a cloudy day version with a uniform background lighting and sure enough the milk renders creamy white again.
Looks pretty close to Henrik Wann Jenson's milk pic above

So I can go back to my watered down version to speed up the render!

Now does real milk go blue under direct sunlight?

another thing, does milk thin out much when inside in a narrow container?
There doesn't seem to be much thinning out of the milk at the top on the glass object in these renders

CoolColJ · Post by **CoolColJ** » Wed Sep 19, 2007 4:57 pm

I found my answer I think

Make blue light

What you do:
Fill the plastic drinking glass about 2/3 full of water. Add ½ to 1 teaspoon of milk and stir. Take the glass and torch into a darkened room. Hold the torch above the surface of the water and look at the water in the glass from the side. It should have a slight bluish tint.

The colours in the light from the torch are being scattered by the tiny, tiny bits of milk in the water. Just like the colour blue in sunlight is scattered by the tiny, tiny bits of air in the atmosphere.

Changing the colour balance from D65 to D75 or 9300K lessens the blue tone a bit as well.

CoolColJ · Post by **CoolColJ** » Wed Sep 19, 2007 6:38 pm

well I took a real glass of milk out into the sun and it doesn't turn blue, so who knows

either the Sun is too strong or something wrong with the data

Kram1032 · Post by **Kram1032** » Thu Sep 20, 2007 2:03 am

...or it's the difference between your sky and the indigo sky...
...or it's due to missing atmospheric scattering in the standard indigo sky...
try to add a bottle, filled with milk, to globe.igs (if you're able to handedit it^^), then, you'll see, whether or not it looks blue

- And it might be quite hard to tell, if the milk gets blue, for real, as the simple fact of KNOWING milk as white (yellowish), let you also THINK, it's white (yellowish)...

CoolColJ · Post by **CoolColJ** » Thu Sep 20, 2007 11:06 am

Well the milk has a yellowish white absorbtion colour in sketchup once you load the IGM

which is what you see, and still see somehow with that massive scattering values of <rgb>18205.267 20382.600 22369.800</rgb> !

until you put it under sunlight that is. That scattering value has more red in than anything, so that means more red and green is scattered, so leaving the blue in there I think...which is what you sort of see in the skim milk in the Henrik Wann Jenson pic. But that is more watered down than regular milk.

Now watered down milk does go blue in weak light as shown in the above photo. Now if milk goes blue in Indigo under sunlight that would mean that milk is too "weak" doesn't have enough absorbtion maybe, or the sun is too strong

well I know milk is white in sunlight as I took a glass of milk outside yesterday to check

suvakas · Post by **suvakas** » Thu Sep 20, 2007 3:25 pm

lol
Indigo's goal = a good milk renderer?

I think those milk results are Ok.

absorption and scattering coefficients for liquids

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