Papercut Stop Motion Stylized Fire
I’ve absolutely love mixed media animation, and one of my biggest interests in computer graphics is stylized animation. For this project, I wanted to use procedural techniques in Houdini to mimic a papercut animation style.
I ended up using Houdini to create masks for the paper layers of the fire and then comping them together in After Effects using pictures of paper I took.
I’m very excited about how it came out, and I’m hoping to combine this technique with real papercut animation in the future.
The final result is to the right!
Breakdown
Pyro Sim
The effect is driven primarily by a pyro sim. Because I only needed a general silhouette of a 2D slice, I was able to get away with simulating only a small volume of fire at a relatively low resolution, so the simulation ran in near real time.
I fiddled for a long time to get the right parameters for a good fire effect, focusing on creating interesting shapes as the fire trailed off. I also applied a sin wave based velocity field to help make the fire hit more wavy graphic shapes like cartoon fire.
Papercut Effect
To create the final papercut effect, I took a volume slice of the pyro sim. I then split it into three different parts based on temperature to create the stepped look of the fire. Each of these parts was separately surfaced, creating a mesh that was easier to manipulate for the papercut effect.
With the new meshes, I then applied a series of position smoothing (both distance based and curvature based) and position blurring to get the papercut look. I also blended each frame of animation with adjacent frames to smooth out the animation and prevent too much flickering over time.