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th3ta
03-04-2012, 05:16 PM
The coke zero liquid on the right is the exact look I'm trying to achieve. I've tried contacting the artist who did it, but I haven't heard back yet. On his blog he mentioned something about it being a simulation of caustics - using multiple planes(or lights?) behind and inside the bottle to create caustics that give it that look. Does anyone have experience using that method to get this look?

I started getting something vaguely similar, but the light sources just illuminate the whole bottle and there aren't clearly defined regions of color like in the ref image.

I can use Mental Ray or Vray to render. Anyone have some tips?



http://www.kumodot.com/wp-content/uploads/2011/03/coca_foto_e_cg.jpg

pokoy
03-05-2012, 04:42 PM
I don't think these are caustics (at least not the kind of caustics used in the CG terminology) but rather, as you already said, refractions and/or reflections of objects behind the bottle.

No one except the author can tell what exactly he has used but usually you'd map a radial gradient on a plane and place several of these planes behind or at the sides of the bottle, at different distances. Play with positions and scaling of those planes and pay make sure their material is self-illuminating so they remain well visible in reflections and refractions.
Also, exclude those planes from generating and receiving shadows and GI and make them invisible for the camera, they should be visible for reflections/refractions only.


It needs a lot of tweaking so don't give up too soon ;)

DanGrover
03-06-2012, 08:55 AM
I don't think these are caustics (at least not the kind of caustics used in the CG terminology) but rather, as you already said, refractions and/or reflections of objects behind the bottle.

No one except the author can tell what exactly he has used but usually you'd map a radial gradient on a plane and place several of these planes behind or at the sides of the bottle, at different distances. Play with positions and scaling of those planes and pay make sure their material is self-illuminating so they remain well visible in reflections and refractions.
Also, exclude those planes from generating and receiving shadows and GI and make them invisible for the camera, they should be visible for reflections/refractions only.


It needs a lot of tweaking so don't give up too soon ;)

Indeed - and it's one of those times where a GPU renderer on the side like Vray RT makes a world of difference! You can see more-or-less immediately whether something is working or not!

th3ta
03-07-2012, 02:16 AM
Thanks for the info guys. I've got something working pretty well now, multiple planes with radial/noise grad positioned in the liquid. It really does just take trial and error to get something decent.

pokoy
03-07-2012, 08:33 AM
Glad it worked. You placed them in the liquid? Normally you place them outside of the bottle like in a real life photography setup. But it doesn't really matter as long as it works ;)

th3ta
03-07-2012, 05:30 PM
Yeah I ended up placing them inside the liquid. I tried outside and behind the bottle, but they weren't showing through the liquid.

pokoy
03-07-2012, 07:56 PM
I see, you probably have to increase refraction ray depth. If a ray has to go through 3 different materials and each of them is 2-sided, you have to set it to 12 (6 rays to get through them and 6 to get back to camera again). I might be wrong and it might be something different but if it's at the default value (8) it's probably the reason.

th3ta
03-07-2012, 09:13 PM
Ahh ok. Thanks for the tip, I'll mess around with that and see if it helps.

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