Shading

Shading refers to the depiction of depth perception in 3D models (within the field of 3D computer graphics) or illustrations (in visual art) by varying the level of darkness.

In computer graphics, shading refers to the process of altering the color of an object/surface/polygon in the 3D scene, based on things like (but not limited to) the surface's angle to lights, its distance from lights, its angle to the camera and material properties (e.g. bidirectional reflectance distribution function) to create a photorealistic effect.

This type of light source is mainly used to provide the scene with a basic view of the different objects in it.

This produces diffused, non-directional lighting throughout the scene, casting no clear shadows, but with enclosed and sheltered areas darkened.

Models a spotlight: light originates from a single point and spreads outward in a cone.

A directional light source illuminates all objects equally from a given direction, like an area light of infinite size and infinite distance from the scene; there is shading, but cannot be any distance falloff.

Theoretically, two surfaces which are parallel are illuminated virtually the same amount from a distant unblocked light source such as the sun.

The distance falloff effect produces images which have more shading and so would be realistic for proximal light sources.

Distance falloff can be calculated in a number of ways: During shading a surface normal is often needed for lighting computation.

If a specular highlight doesn't fall on the representative point, it is missed entirely.

Bishop and Weimer [9] proposed to use a Taylor series expansion of the resulting expression from applying an illumination model and bilinear interpolation of the normals.

Spherical linear interpolation (Slerp) was used by Kuij and Blake[11] for computing both the normal over the polygon, as well as the vector in the direction to the light source.

Based on an image's shading, a three-dimensional model can be reconstructed from a single photograph.