# Cycling AbsorptionVolume for Water

• Hello

I dont understand the AbsorptionVolume. I want the effect for water the deeper the more blue. But the AbsorptionVolume effect does not work. At the right bottom corner of the Pic I've used the AbsorptionVolume. But it should be wihte transparent at the edge and more blue in the deeper water, but it has the same blue everywhere.

I realy don't understand the AbsorptionVolume. Can anybody help explain me how the AbsorptionVolume should work?

• Here is a view from the top.
Left side is water with 0.0001 density blue apsorption. All is the same blue. Thers's no diffrence between the depth of the water.
The right side of the pic is no absorption.

Either the AbsorptionVolum does not work correctly or I don't understand this function.

I hope anybody can explain me why. The water is a cube.. Caustic refraction is on.

• This post is deleted!

• @joker I think the absorption node needs a model with thickness to it. You have a 2-d plane going on here right? Same thing happens with SSS and Volume Scatter. The model it is placed on needs some thickness to it (a cube instead of a 1 sided square)

• @joker ok I did not read your entire post. you are using a thick object. The issue is that, in this example, you ARE using a cube and the cube has equal thickness all around so absorption happens the the same everywhere in the cube. You have to have a puddle shaped object for the absorption to work correctly.

• @ghostship

Hello ghostship

No I use a cube, not a square. It's strange...

• sorry my english, what do you mean with puddle?

you think I should take a flat cube with less depth?

Or it must have the exact shape of the puddle. i think

• @joker take a look at my second post. Here is an example of how absorption works. See how it is darker on the thicker parts of Andy.

• Ok, That means it only works to the whole shape but not if another object is passing through this shape like in my exapmple where floor is passing through the cube?

• @joker yeah, the model needs to be puddle shaped to work correctly.

• @ghostship Thank you very much I would never have come here myself

• @ghostship

Another question is: It's realy not possible to make an under water szene with blue absorbing water and objects inside like fishes and so? Or is there another shader for that?

• @joker that might be easier to do with a giant cube.

• @ghostship

I don't realy understand what you mean. You was right, the absorbtion doesn't work with other objects inside or passing through.

Andy at the right side and the cube has both the same materials with absorbtion. It works with single Andy at the right side.
But it does not work if anything is inside a light absorbing object like Andy inside the cube. He has all over the same blue color. But that's not how I expect it in reality. Andy should getting more darkerblue as deeper he is tndide the cube.

Raelistic water with objects inside it doesn't work this way. I dont understand what you mean with a giant cube should be easier?

• @joker without checking it out myself I assumed the "cube as large body of water" should work but it is not in your example. What if the cube was massive? That might have an effect where the cube was much bigger than the floating object inside. Or you could play with the density settings and use a smaller object in this cube.

• @ghostship

Thank you for your answer. I'm afraid that also will not work, but I will try.
Till now I used the z-depth layer, make it blue and multiply it with the szene in a paint app, so I get e deep blue effect for whole underwater szenes.

• Hey guys - sorry I'm not participating much lately - swamped with work.

I didn't read all of the above too closely but it sounded like there's a belief that the absorption only works with a solid. That is not consistent with my experience.

Here's a single plane on the left (with pink absorption color) and a large box on the right (with blue absorption color). The ground has a simple tile shader and has been morphed to have hills and valleys.

I clearly see the variable amount of absorption both under the plane and inside the box.

If you're not getting this, I'm guessing there's some other setting or property you've messed with.

• Here's the shader I used - nothing special except it has the "Tricky glass" technique to give fast lighting under water.

• @bagginsbill The conclusion I come to is that scatter and absorption both vary in effect depending on the geometry thickness.

• @bagginsbill Thank you very much :-)

Yes, it works, but with your "Tricky glass" technique only. It doesn't work with a simply refraction.