Gears of Washroom – Pt 6

Last post was all about materials, this time around I’ll be talking rendering settings and lighting.

Rendering choices

Being one of my first renders in Houdini, I made lots of mistakes and probably made lots of poor decisions in the final render.

I experimented a bit with Renderman in Houdini, but after taking quite some time to get it set up properly, enable all the not so obvious settings for subdivision, etc, I decided this probably wasn’t the project for it.

I ended up using Mantra Physically Based Rendering, and chose to render at 1080p, 48 fps. Well… I actually rendered at 60 fps, but realized that I didn’t like the timing very much when I’d finished, and 48 fps looked better.
This is something I should have caught a lot earlier 🙂

Scene Lighting

I wanted two light sources: an area light in the roof, and the explosion itself.
Both of these I just dumped in from the shelf tools.

The explosion lighting is generated from a Volume Light, which I pointed at my Pyro sim.

I was having quite a lot of flickering from the volume light, though.
I suspected that when the volume was too close to the walls, and probably a bit too rough.

To solve this, I messed around with the volume a bit before using it at a light source:

VolumeLight

So I import the sim, drop the resolution, blur it, then fade it out near the wall with a wrangle:

VolumeTrim

For the sake of the gif, I split the wall fading and density drop into separate steps, but I’m doing both those things at once in the Wrangle:

@density -= 0.12;
float scale = fit(@P.x, -75, -40, 0, .2);
@density *= scale;

So between a X value of -75 (just in front of the wall) to -40, I’m fading the volume density up from 0 to 0.2.

After that, I had no issues with flickering, and the volume lighting looked the way I wanted it!

VolumeLightFrame.png

Render time!

I think that’s it all covered!

Some stats, in case you’re interested:

  • Explosion fluid and pyro took 3 hours to sim
  • Close up bubbling fluid took about 1 hour to sim
  • Miscellaneous other RBD sims, caches, etc, about 2 hours
  • 184gb of simulation and cache data for the scene
  • Frame render times between 10 – 25 minutes each.
  • Full animation took about 154 hours to render.
    Plus probably another 40-50 hours of mistakes.
  • 12gb of rendered frames

My PC is a i7-5930k with a NVidia GeForce 970.

Hopefully I’ve covered everything that people might be interested in, but if there’s anything I’ve glossed over, feel free to ask questions in the comments 🙂

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