Simple illumination model

In order to express the natural illumination phenomenon in computer graphics, it is necessary to establish a mathematical model according to the relevant laws of optical physics to calculate the brightness of any point on the surface of the scene to the observer’s eye, which is called illumination model.

The illumination model includes many factors, such as the type of object, the position of the object relative to the light source and other objects, the attribute of the light source set in the scene, the transparency of the object, the surface brightness of the object, and even the various surface textures of the object.

Light sources with different shapes, colors and positions can bring different lighting effects to a scene. Once the optical properties of the object surface, the relative position of each face in the scene, the color and position of the light source, the position of the viewing plane and other information are determined, the light intensity value transmitted by a point on the object surface in the viewing direction can be calculated according to the illumination model.

When the light reaches the surface of the object, the object will reflect, transmit, absorb, diffract, refract and interfere with the light. In the simple light reflection model, the light source is assumed to be a point light source and the object is opaque. It only needs to simulate the reflection phenomenon caused by light illuminating the surface of the object. The simple illumination model is that the incident light is equal to the diffuse light plus the mirror reflected light plus the ambient light.

Among them, diffuse light refers to the light phenomenon of light illuminating rough and dull surfaces, which is characterized by uniform reflection in all directions. Specular reflection is when the light on a smooth surface, especially a shiny surface, may see a strong highlight in a certain direction. Ambient light refers to the indirect influence of the light source on the object. It is a kind of light that is reflected between the object and the environment for many times and finally reaches equilibrium. The light intensity distribution of the ambient light is uniform, and its distribution in any direction is the same.

Your task

What do simple lighting models consist of, and what are their characteristics?

Share your thoughts and ideas in the comments below.