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  • Material based solution for adding water droplets on objects

    Hey there,

    I am trying to figure out a way to get water droplets on a surface without using geometry. So, lets say I have a bottle with liquid in it, lets assume it's a bottle of beer, hehe. Now, I have an object for the glass itself, which has some thickness modeled into. And then I have an object for the liquid which is penetrating the glass object slightly to render as an surface-surface-interface, like in the vray example section.

    For the droplets I used to have some techniques of adding geometry droplets on the surface (pflow, scatter, placing by hand, whatever...). This DOES do what I need, but it's really lots of work to get the droplets just right.

    Now it would be nice if I could replace the geometry-droplets techniques by a shader-based solution, probably using some form of displacement and/or normal mapping techniques.

    So, my first attempt was to just use a vrayblendmtl to layer a "droplet"-material with normal map for the droplets (that I created with photoshop and zbrush) over the glass-material. For the reflection part this does work. But the correct refractions behind the drops that would be visible in reality (because of the droplets standing out of the surface) don't come out right, of course, since there is no real thickness in the coat layer. I also tried to copy the original geometry, put a droplet-displacement map on it put the water-refraction material onto it. This does work to some extend, as now the refractions get distorted correctly onto the surface of the glass. But this does not seem to be the best solution anyway. So, has anyone any idea on how to accomplish this? This should work as a general solution to render drops on various objects, since I have to do this frequently on different models...
    Here is a custom mental ray shader, that looks like it does what I am searching for in Vray:

    http://www.3dcg.net/software/minwetness


    Hope you get what I mean. Any advices would be great.

    Thanks in advance

    Greetz Ben

  • #2
    I guess I'd go for either one or the other method you already tried, leaving normal maps alone though, and using displacement for both.

    Comment


    • #3
      check out Brett Simms thread:

      http://www.chaosgroup.com/forums/vbu...water+droplets
      chris
      www.arc-media.co.uk

      Comment


      • #4
        Thanks for that link. Indeed, the results looks pretty nice, the best I've seen so far. So, in essence, he uses the same workflow as I did yesterday in my tests. So, thanks... I will go and play some more with this kind of technique...

        Comment


        • #5
          I have used both methods (geometry and displacement) as well as just normal mapping and they all can work okay. Normal mapping is good for distant shots, or for really fine 'micro-sweat' type condensation, but it doesn't work well enough for large drops IMO.

          The key thing for displacement is getting a good map. Most of the ones you will see/find don't have very nice shapes, and then tend to look spiky - with too sharp peaks to them. If you take your time on that part the rest should go smoothly.

          My preference these days is for geo droplets as I like being able to customize the pattern more, but the distribution can be a pain. VrayScatter was how I did the last one but that software is kinda buggy. MultiScatter might be better but I just wasn't that interested in spending more money with those guys - not thrilled with the support.

          Good luck with it.
          b
          Brett Simms

          www.heavyartillery.com
          e: brett@heavyartillery.com

          Comment


          • #6
            Thanks for your advice Brett. The geometry method did work for me in the past. The best way I found was to use Pflow in conjunction with Pwrapper. So I made a Pflow with particles spawning from the objects surface, bound them to surface, let them run down the surface a bit an then spawned another 5-6 particles from these "birth"-particles and let them spread randomly in all directions.. jsut a little. Then used Pwrapper to build single drops out the 5-6 particle clusters. This way you can get some really nice looking, all different shaped droplets, which also seem to be slightly running down the bottle mimicking some gravity effects. In fact I did about 5-6 different pflow-streams like this and changed the parameters a bit to get even more randomness. This works quite ok. BUT, as you said, this is quite a lot of work to get the distribution just right. However, what I was really searching for is a complete shader-based solutions. This IS possible, no doubt. Creating displacement maps for the drops should be the least problem I guess. I tried some workflows with photoshop and ZBrush and that works quite well and I get nice drop shapes. So, the beauty of this (for me) would be that if I once have a good map, it can simply be reused without effort on all kinds of objects, without having to do the Pflow-Setup over and over again for every single object. Also, the scenes don't get that heavy as with geo-drops. I did some rendering in large print resolution and ended up with millions of polys just for the droplets which makes handling the scene more complicated.
            However, I think I will test out the displacement workflow some more, as I got some nice early results with it today. Have to look though how this works for large print images and how displacement will affect render times more than geo objects. I will come back with some test here...

            Thanks all for your help so far

            Greets Ben
            Last edited by Wobi; 04-03-2011, 01:00 PM.

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            • #7
              referenced

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              • #8
                I have worked with Pwrapper and Pflow to do this as well - spent some reasonable hours testing that approach. My feeling is that it is great for creating natural looking runs in the droplets, but I still prefer the hand-built drops and the displacement map we made works wonders where droplet level control is not needed.

                Below is another example of one that is done with geometry for the large drops, and a bump map for the fine drops (I'm pretty sure it was bump map, but its been a while and I didn't feel like un-archiving the scene just to find out ) I think both methods are very good, but I have never seen anything done with procedural shader approaches that worked well. Just my experience and YMMV, but I did try very hard to make that work too - it's by far the easiest way. It never came close the kind of detail/realism I got with the other methods (like the one below, you can see a crop of the hi-res and the detail is pretty good IMO).





                Brett Simms

                www.heavyartillery.com
                e: brett@heavyartillery.com

                Comment


                • #9
                  Very nice droplets. A simple image can look so good sometimes !
                  Regards

                  Steve

                  My Portfolio

                  Comment


                  • #10
                    Brett:
                    try using Forest Pack! i ve recentyl quit using Multiscatter because of the same reasons as you did and started using Forest Pack.
                    Not only the support is great, but the speed of rendering is miles better.
                    Great image BTW
                    Martin
                    http://www.pixelbox.cz

                    Comment


                    • #11
                      Thanks Steve and Martin

                      Martin: I thought about Forest Pack and had a few email exchanges with Carlos, but he indicated that this kind of thing wouldn't work with FPP because it didn't have the scatter by 3D surface tools necessary. I have been waiting for a suitable version to come along.

                      /b
                      Brett Simms

                      www.heavyartillery.com
                      e: brett@heavyartillery.com

                      Comment

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