MatCap
Lit-sphere material that needs no lights
Also known as: Material capture · MatCap Blender · MatCap ZBrush · Solid mode matcap · Matcap shading
Definition
A MatCap, short for material capture, is a texture of a lit sphere that is applied to a mesh according to the direction of its surface normals, so the model appears shaded and lit without any lights or real material calculations. It is cheap and fast, and gives a stable look from any angle, which is why sculpting tools use it. ZBrush uses MatCaps for its viewport shading, and Blender's Solid mode can use them, with a different image for different looks.
In production
Use a neutral gray MatCap to judge form and a more contrasty one to see small details, and switch between them to find problems. A MatCap shows shape, not color or realistic lighting, so it should not be used to judge textures or materials. You can make your own from a photo or render of a sphere, and use them in portfolio screenshots of sculpts.
