illuminiation model

Photorealistic representation of bodies and models goes far beyond surface representation, which is perfectly adequate for technical and scientific applications. Photorealistic computer graphics works with surface structures and with illumination and the related effects of light reflection, refraction and shading.

Light is diffracted, refracted and reflected on the surface of bodies. These physical laws are surface and material dependent and can be emphasized by indirect, diffuse, point or directional lighting.

Indirect lighting, ambient ligthing, forms the simplest lighting model. In this lighting model, light is diffused from the environment so that it shines evenly on the object from all sides. It is impossible to tell from which direction it comes. The light reflections on the body surfaces scatter evenly in all directions.

In diffuse lighting, light is reflected from the body in all directions, there is no point of increased brightness, all surfaces appear equally bright.

In point lighting, a point of increased brightness appears on the body. The brightness of this point is strongly dependent on the distance of the point light source from the body and on the strength of the indirect lighting.

Directional lighting, specular lighting, creates directional reflections. The light comes from a specific direction and is reflected in from the body surface in a specific direction. The viewer sees the reflection only at a certain angle. If the observer deviates from the angle of ideal reflection, the intensity of the reflected light decreases relatively quickly. This specular value is strongly dependent on the surface and material properties of the body. Just think of a body made of rubber, which has a different reflection than one made of metal. If the observer is in the direction of the reflection, a bright specular light appears at high specular values.