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# 1 11-01-2014 , 01:53 PM
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Photorealistic water doplets and sweat

Hi everyone,

I'm trying to once and for all find a good method for creating realistic droplets and "sweat" on glass bottles.
There several topic to be find online and lot's of techniques but I haven't found one yet that works for me.

What I'm after:
Very dense populated fine "sweat" drops, suited for close ups and some bigger droplets here and there -> see Heineken image example.

What I've tried so far:
- Maya paint brush with water droplets brush from the visor (Beck's image). Problems: it created drops that go inside each other which can't happen in real life. Only way around this is to delete all the drops that are sitting in each other but it's a painfull and inefficient process.
- Realfow with texture maps from this tutorial: https://www.digitaltutors.com/tutoria...ng-in-RealFlow . Problems: could not get enough detail (the texture maps I use are high resolution with lots and lots of small drops).
-Bump maps and displacements: Bump maps doesn't cut it for me with close-ups and the sides of the bottle. Displacements are better but take too long to render and I cant find a good way to create water displacements on the labels. Even only on the glass, for me it's noticeable if you just use the glass material for displacements instead of true water material (because of the different refractive index).
- I even tried to convert displacement to polygons in maya, then use that geometry with a opacity mask so only the drops would show. It's getting there but again with the labels I run into problems.

I believe the best way (in terms of realism and render speed) is having polygons for drops. But I'm all out of ideas to try :p. The becks image is done with maya paint brush but as you can see some drops sit in each other and is not acceptable for me.
If there's somebody with the magic method I'd love to hear it!


My best try:
user added image

Desired result:
user added image





Cheers

# 2 11-01-2014 , 09:17 PM
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# 3 11-01-2014 , 10:59 PM
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That is pretty cool. In C4D I always used XPresso and Thinking Particles. This even appears to have speed stretching.

# 4 14-01-2014 , 03:09 PM
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Thanks for the replies.
I've been playing around with that script and it looks very promising.
Altough I've run into a problem: the sweat drops are not placed on top of the surface but in the middle so it "digs" into the model which will be visible in the renders.

user added image

Anyway around this? (apart from scaling them, which is not the work around I'm looking for).
Cheers

# 5 14-01-2014 , 04:02 PM
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Once you're happy with the layout of the drops, combine them into one object, and boolean cut them with the bottle.

You might need to up your res, and might have some jagged edges, but it may suffice for your purpose. If you were using renderman you could do this boolean operation at render time - I'm not sure if mental ray or maya's rendered have a similar option though.

cheers

gubar

# 6 14-01-2014 , 04:27 PM
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Alright I'll give that a try. So you mean:
- Convert nParticles to geometry
- Then use the bottle mesh for boolean

Is there a way then to boolean and create closed caps on the remaining drops? Otherwise it will not refract realistically when rendering (I'm using Maxwell render).

# 7 14-01-2014 , 05:06 PM
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Hmm, when I try boolean, everything just disappears... I tried both orders of selections.

user added image

# 8 14-01-2014 , 06:23 PM
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If boolean failing it usually means objects have history - clean your scene by deleting history. Peeps always go on about booleans not working but I use them all the time - but I keep my messes clean hehehee


# 9 14-01-2014 , 06:31 PM
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I've already deleted all the history and the mesh is clean.
I found out that it only works with 1 drop as a separate object, not when all the drops are combined like this. But that would mean I have to boolean each drop separately, and that's not really a possibility.

# 10 14-01-2014 , 06:32 PM
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Try subdividing your geometry again before you boolean.

# 11 14-01-2014 , 07:14 PM
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Adding resolution to the drops with the "smooth" option you mean?

# 12 14-01-2014 , 09:59 PM
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Yes, I'd give it a try. If you want to upload the scene I could take a quick look tomorrow,

# 13 15-01-2014 , 03:31 AM
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Genny had a script in here somewhere too, dont know if its the same one. Yeh gubar has the right idea, if the 2 meshes have significant geo differences in subdivision levels it wont work. Tweety was also correct, booleans are a pain to learn but I use them a lot.

cheers bullet


bullet1968

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# 14 15-01-2014 , 11:39 AM
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# 15 15-01-2014 , 11:45 AM
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Hello dvhouw

I think your becks spritzing is pretty convincing.
If it's just for a still image you could render the droplets out separately and comp them on in photoshop without booling them. I've used this method before, you can create masks by using surface shaders in a separate render layer.
Having worked in retouching I know that hero shots like the Heineken provided have had hours of retouching done, usually from several studio shots and lighting setups comped together in photoshop (look at the less amount of droplets on the label). I've tried to do spritzing before on a beer glass by emitting particles at a glass but have never been happy with the results.

I'm interested to see how you get on - good luck.

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