In computer graphics shading is referred to as the process of altering the color of an object in the 3D scene based on the surface angle to lights, its distance from the light, and the material properties. Constant intensity is also known as flat shading. This is the most simple and very fast method to specify a color of an object. Flat shading of a polygon assumes that each polygon is strictly planar and all the points on the polygon have exactly the same blind light treatment. In this method, a single intensity is calculated for each polygon.
This technique thus displays all the points in a polygon with a single color. In this method, the main idea is that we use only one surface normal per polygon.
In general, flat shading of polygon facets provides an accurate rendering for an object if all the following are valid:
- The object is a polyhedron and is not an approximation of an object with a curved surface.
- Light sources illuminating the objects are sufficiently far from the surface so that the unit is normal to a surface; unit direction vector to the point light source from a position on a surface and attenuation is constant over the surface.
- the vector position is sufficiently far from the surface so that the unit vector pointer to the viewer from the surface position, a unit vector in the diversion of ideal specular reflection is constant over a surface.
Advantage:
- Constant shading can be useful for quickly displaying the general appearance of a curved surface.
Disadvantage:
- One of the disadvantages of constant-intensity shading is a very poor display of polygon-mesh approximations to curved surfaces.