Stylized Toon Shading in Arnold: Hatching, Shadow Masks and Per-Object Controls

[forrest.brent]

Stylized Toon Shading in Arnold: Hatching, Shadow Masks and Per-Object Controls

I recently put together a video walking through some of the techniques I use when building stylized, non-PBR shaders in Arnold for Maya.

This isn’t really a “build this exact shader” tutorial. It’s more about showing how a few fairly simple Arnold and Maya nodes can be combined to produce inconventional results.

In the video I start with aiToon and gradually build on top of it using ramps, projections, sampler information, noise and custom attributes.

Some of the things covered include:

• Creating line and cross-hatching style patterns with ramps

• Using camera projection to keep hatch directions consistent on screen

• Using surface luminance to isolate light and shadow regions

• Distorting and varying Arnold contour widths with procedural noise

• Driving toon-shader properties using aiUserFloat

• Creating per-object color overrides with aiUserColor

• Adding custom Arnold attributes directly to Maya shape nodes

• Using one shader across many objects while still allowing individual objects to have different colors, line widths and other properties

• Experimenting with Arnold utility, math and color nodes to push the result further

One of the techniques I find particularly useful is using custom attributes on the shape itself.

Instead of creating five or ten nearly identical shaders for different objects in a scene, you can build one larger shader network and expose selected parameters through Arnold user-data nodes. Each shape can then carry its own values for things such as line width or color while continuing to use the same material.

The other area I spend some time on is deliberately abusing fairly ordinary texture nodes. A ramp doesn’t necessarily have to behave like a conventional texture. Once you start feeding it through UV transforms, camera projections, noise, luminance information and remapping nodes, it becomes a useful building block for hatching, graphic shadow patterns and other NPR effects.

A lot of these are techniques I wish I had found documented when I first started experimenting with Arnold outside of conventional physically based rendering, so I hope there’s something useful in here for anyone else interested in pushing aiToon a little further.

Video: