Procedural Animation

Spider Automata done with Houdini


3/17/20233 min read

Project Brief

Inspired by various automatas, I wanted to attempt making a procedurally animated automata of a subject that I have my personal interest of. I gathered multiple references for both visuals and research, and brainstormed how I would make the mechanics work. I chose my automation to be a spider, specifically a sydney funnel spider, and simulate its movements with CHOPs animations and intersection analysis for the gear mechanics.


After gathering references of different automata references, I set the mechanical reference of my automata to be Cecilia Schiller’s A Walk in the Park. Implying that walk cycle, I came up with two possible movements that I attempted to simulate.

One, back & forth animation of each spider legs, varying by left & right and even & odd number order of its leg. It would be simulating a more realistic movement. I would have been using two-point constraints for the leg’s vertical movement, and CHOPs and intersection analysis for each the horizontal movement and gear movements.

Two, up & down movement for each spider legs, also varying by left & right and even & odd number order of its leg. It would be simulating more of a toy-like movement, and it has a simpler mechanic. This was sort of a fool-proof mechanic for me as I could imagine it working it without too much struggle. After attempting both methods, I decided to work with the second method as the first method was requiring more complex mathematical calculations to match the curved radius of the movement. My ideation process is documented in this proposal document:

Technical Guide

1. CHOP Legs

Each legs vary it’s movement by its location from the spider’s body. There are two sets of movements fed by CHOP fx that feeds the expression to the legs of each set.

The movement of the legs and the gear were matched matched manually without any use of expression.

2. Intersection Analysis Gear

The mismatching movement of the gear was simulated by placing the center of the gear off-center, 180 degrees away from the one attached on the opposite side of the rod.

Intersection analysis is fed separately to each end of the rod, later to be fed on the up&down motion of the stem that will be attached directly to the spiders leg. This is done by using the point expression (point(0,0,0,0)).



Cecilia Schiller's A Walk in the Park.

You can see it in action [here]

Frame 1 Frame 10.

Notice how the odd numbered legs are up.