The curvature shader is an easy way to add detail and realism to your shaders. In this short tutorial, we will use the curvature shader to create a wear and tear shading effect. It will be used to represent where the edges of a hard surface are scraped on the model of a mech. Notice in the image above how the edges of the paint appear worn off, exposing the metal underneath.

Note: You can use either a layer shader or a mix_shader in this tutorial.

The shader used in this scene can be downloaded here.

Layer Standard Surface Shaders

A Layer shader is used to layer two different standard_surface shaders. We will use one standard_surface shader for the top metal paint layer (green) and another standard_surface shader to represent the exposed metallic surface underneath.

• Create a Layer shader and connect it to the Arnold Beauty port.
• Create a standard_surface shader and rename it Green Paint. Connect it to Layer 1 of the Layer shader.
• Create another standard_surface shader and rename it Metal. Connect it to Layer 2 of the Layer shader.

Curvature Shader

• Connect a noise shader to the radius of a curvature shader (bias and multiply will work too). Experiment with different noise settings to get the look that you want. Don't forget that you can connect a color_correct shader to the noise shader to further refine the appearance of the 'worn' look.
• Connect the curvature shader to the Layer 2 alpha of the Layer shader. This will control the blending between the two standard_surface shaders.

Without noise shader	With noise shader

Bias

• In the example images below, the bias parameter of the curvature shader has been increased and exaggerated to better demonstrate the effect.

bias: 0	bias: 0.5 (default)	bias: 1

Samples

• Increasing the number of curvature samples reduces noise and gives a better quality result.

curvature_samples: 3	curvature_samples: 6

_{Final shader network}