Creating Artificial Rain

While beta testing the Mac version of HitFilm 2 Ultimate, I decided to try create the effect of rain hitting a window.  So I sprayed my window with a garden hose, took a photo of the drops of water, and created some particle textures.  Then I applied them to a couple of particle systems, and created this video:
http://youtu.be/DQHfXTKbNrQ
I used some random footage from a few years back, and I realize that its pretty obvious that I'm not getting hit by any raindrops, nor is the surface of the water in the BG.  But the illusion that there is a window between the camera and the subject seems to work pretty effectively. 

Comments

  • Very nice effect! Are you using a deflector for the window pane?
  • Triem23
    Triem23 Posts: 20,279 Power User
    Yes, very nice. Once you get the Mac version into release, this should be a tutorial. This would also work for the popular "blood hits the lens" effect. Are you using the particle layer to drive a displacement layer to get the refractive effect?
  • AxelWilkinson
    AxelWilkinson Posts: 5,255 Staff
    I originally started by using a deflector, then setting up normal falling rain as mobile emitters, which could activate on impact with the deflector to create a splatter.  In the end, though, it was easier to just create a large rectangular emitter and use that as the window pane, and with the speed set to 0, the particles just appear and stay put, as if drops were hitting the window.  For the ones that run, I used mobile emitters, so that they could emit particles as gravity pulls them downward, to crate the trail.
    I then duplicated my footage layer, used the particle effect to displace it, and then used a set matte effect to apply the alpha of the particles as well.  By using a second layer in this way, I could add a bit of blur, to defocus the drops without affecting the underlying footage.  I expect that I will do a proper tutorial somewhere down the road.
  • Thankyou for the breakdown
  • AxelWilkinson
    AxelWilkinson Posts: 5,255 Staff
    Of course, this is the sort of effect which would be pretty easy to do practically in most cases, but its still fun, and could be useful in some situations.
  • StormyKnight
    StormyKnight Posts: 2,618 Ambassador
    edited October 2013
    Perhaps on the window of a CG decontamination chamber. :) 
  • karma
    karma Posts: 163 Enthusiast
    This is great.  Is there any way you can share this project.  It is PERFECT for some things I need to do and you seemed to have really nailed it.
    Mike
  • Triem23
    Triem23 Posts: 20,279 Power User

    Perhaps on the window of a CG decontamination chamber. :) 
    Or an out-of-cockpit shot of, say, a fighter flying through rain, clouds or heavy fog with condensation--adjust the forces so the streaks get pushed outwards from wind...
  • SimonKJones
    SimonKJones Posts: 4,370 Enthusiast
    Yeah, while this would be relatively easy to do practically in a lot of cases, for CG shots this technique is super useful and adds a sense of atmosphere.
  • Triem23
    Triem23 Posts: 20,279 Power User
    If I were shooting a practical location, I would be more likely to try for practical water, but for any blue or greenscreen work, I would be more likely to use a technique similar to what Axel came up with. (I wouldn't even put practical windowpanes on a chromakey set. Reflections, refractions and spill end up being a nightmare.)
  • Nate066
    Nate066 Posts: 190 Just Starting Out*
    If I were shooting a practical location, I would be more likely to try for practical water, but for any blue or greenscreen work, I would be more likely to use a technique similar to what Axel came up with. (I wouldn't even put practical windowpanes on a chromakey set. Reflections, refractions and spill end up being a nightmare.)

    you are correct, reflections are very hard or impossible to key without tons of manual work

  • Triem23
    Triem23 Posts: 20,279 Power User
    My buddy Dan Novy (Emmy Winner, Oscar Nominee) tells stories about "The Adventures of Pluto Nash," where lights would be reflecting off spacesuit helmets. God forbid anyone make Eddie Murphy wait an hour for a re-light.... Nope, three months of post-production with a team of five VFX guys having to hand-retouch/roto all the problems. This has nothing to do with Axel's rain sim, but a lot to do with issues of chromakey and glass. (Incidentally, Mr. Novy is very impressed with the toolset and quality of output Hitfilm is capable of, and this is a guy whose Emmy and Oscar-nomination were for VFX.)