!!PLS!! help me with this ! i stuck in this theory for 3 days already!!!

The image i attached basically explain everything i confuse with.

The absorption node group i downloaded from the internet.
AND IT CONFUSING ME!!!

I made a comparison between all similar shader,
AND I CANT TELL THE DIFFERENCE!

Sorry, i am a bit stupid, i really cant get the idea from it.
can anyone please explain this to me,PLS:(?

2, 3, 4 i added a absorption node on it, and i dun know what those really do,
it was told to be making glass realistic,
but it seem to me just make thing darker, and even more ironic is
when i put 5 next to them ( 5 is just glass shader, nth more) it look pretty well enough,
no need add more node to it.

Q.1 May any1 tell me what this node does and what it applied for? ( i mean people said is applied for glass and make
it become more realistic, but i really want to know what theory they base on support this statement? )

6 and 7 i put volumu shader on it, and also.
i really dun know what it really does,
it just seem to me make all things darker.

Q.2 May Any1 tell me, what volume scatter and volume absorption does? I want to know the theory behind it,
Just like Why it make thing darker, and what it can applied for real life object.

Q.3 Is it the node group i downloaded from just overlap with the function of volume absorption? these two basically
do the same thing if i didnt guess wrong?

Sorry for so much question to ask, but i kind of stuck in here, i did research on wiki, and watch various video
but i just dun get it, it just make me more confuse,
Pls, help me out on this, so i can move on to my learning progress:(
thanks a lot.
i appreciate it.

Attachments



volume absorption test.blend (995 KB)

Seems to be working ok for you. In 2,3 and 4, the difference is in the thinner part of your mesh, which is just what the node setup is supposed to do. That node setup is a quick hack approximating what the volume version does, but rather than sampling within the volume many times, it finds the distance between entry and exit point and apply a colorization based on that. It works like a charm in most cases, at a much faster speed since I can do it with GPU. I haven’t played much with true volumetrics yet, because I don’t really need it for what I do.

If you squeeze your object so that it becomes thin in parts to look through, the effect becomes more apparent.

I still don’t get it:( i try to make the figure thinner, and still, The glass material by itself look decent enough, and that node group
just make thing darker with my limited understanding:(

Well, if glass material by itself look decent enough, why bother with absorption? :smiley: Try with a subdiv’ed and smooth’ed Suzanne. Regular green glass should darken/colorize by same amount everywhere (except for effects of refraction). If you plug in the same node to glass color input, thin parts should get almost no darken/colorize effect. Example image.

Note that in my system, for some really strange reason, my custom absorbent shader in my startup file comes out wrong now, and I can’t believe this is an error I wouldn’t have caught during making (copying) it: For some reason my Ray Length (correct one) output is replaced with Ray Depth (wtf? I never even noticed this output until I noticed it was being plugged into it - not sure when that feature came :p). But from your screenshot, that doesn’t seem to be the case.

Please download a newer version of Blender and use the volume absorption setting. This node group was an ingenious way to simulate absorption effects but is no longer necessary and requires some expertise with the lightpath node to understand.

I think i got what you mean, is about the density of the object thus thin part look bright and
thick part look dark, cuz light trapped inside the object (or absorbed) by high density.
Or did i reversed the order~.~?

thanks a lot carig

Yea, that what i thought too, just wanted to reconfirm it whether this node overlap with volume absorption function cuz this
function weren’t made before the node group come out.