V-Ray for Maya toon shading

Software:
Maya 2018 | V-Ray 3.6

Toon shading in V-Ray consists of two elements:

1. A VRayToon node that creates a graphic contour effect on the rendered image.
2. A flat shader that uses surface luminance data to define color areas.
   * A VRayLightMtl can be used for that.

Creating the VRayToon node:

1. Click the Create V-Ray Toon button in the V-Ray toolbar to create a VRayToon node.
2. In the VRayToon node attributes, set line thickness, color, and more graphic properties.
   * if you created a VRayToon node and it’s not selected RMB click the Create V-Ray Toon button in the V-Ray toolbar and choose Select VRayToon node.
   * To delete the VRayToon node, select it and press Delete.

Creating the toon shader:

1. Create a VRayLightMTL node as the object’s surface shader.
2. Create a Ramp texture node, connect it’s output color to the VRayLightMTL’s color input and delete it’s accompanying 2D placement node.
3. Create a surfaceLuminance node and connect it’s output to the Ramp node’s V Coord input.
4. Optional remapValue node between the surfaceLuminance node and the Ramp node to clamp the luminance values.
5. Optional floatMath node to scale or manipulate the surfaceLuminance output value.

Related:
Arnold for Maya Toon Shading