Sphereflake Animation 2016-02-05
Features
- 480 frames
- 30 frames per second
- 16 second duration
- 1920 x 1280 resolution
- 256 samples per pixel
Story
About a year ago, I created my own path tracing renderer. It's written in Go and has no dependencies besides the standard library. You can find it on GitHub: https://github.com/fogleman/pt
A few days ago, @barrelshifter posted some screenshots of a sphere fractal from her ray tracer. I thought it looked cool, so I decided to replicate it in my path tracer. Here's how that turned out...
That was cool, but then I had the idea of animating it!
I used some easing functions to control the elastic bouncing as each sphere appears and the quick fade out at the end. Each sphere within a population appears with a random offset that follows a normal distribution. I manually specified the mean entry time for each population to make it feel less regular and more spontaneous.
Path traced images can appear very realistic, particularly with well-modeled scenes, as they simulate how light actually behaves in the real world. This results in realistic indirect lighting and shadows.
But it's also very slow. This animation took about 24 hours to render. Most of it was rendered on my home computer but toward the end I launched an Amazon EC2 instance with 36 x 2.9 GHz cores to crank through the remaining frames that had a lot of spheres in them. Even with a k-d tree to accelerate ray intersection tests, the final frames with thousands of spheres were taking 12+ minutes each on my computer. The 36 core instance took 2-3 minutes on each.
To make using EC2 easier, I used Fabric to automate setting up the instances and fetching rendered images from them. Here's my fabfile.py.
Of course, while creating the animation I was able to test it at a much smaller resolution and with far fewer samples per pixel. Then I could render the whole animation in a minute or two.
