My goal is to give my artwork the weathered look of medieval paintings. To accomplish this, I create custom shaders and compositing networks using Side Effects' Houdini software. The shaders cover the painting with craquelure (a pattern of tiny cracks), stains and grime. I also wrote a brush-stroke shader which takes into account the shapes of objects in the painting. This makes it possible to procedurally recreate the look of brush strokes applied by a human painter.

I use various CG techniques to create backgrounds, crowds, and high-detail areas— just as old masters employed apprentices to handle the more mundane aspects of their paintings.

Cavalry created with a crowd system

Distressed wood (digital)

Simulated craquelure
(based on an L-system)

Riders processed with a paint shader.

Researching craquelure led to interesting findings. As it turns out, not all cracks are created equal.

Mud cracks are typically non-hierarchical. Drying mud breaks up uniformly into regions of similar size, which have 6 sides on average.

Craquelure is usually hierarchical. Cracks accumulate over time, forming progressively finer lines. The subdivisions tend to be rectangular rather than hexagonal.

In a hierarchical pattern, cracks form localized regions, which resemble city blocks on a map. Note how width varies among hierarchies.

Hierarchical cracks on glazed ceramics

Hierarchical pattern generated with a computer simulation. Stained glass window, perhaps?