The Properties of Light and Materials

Light and materials are inseparably connected; indeed they actually determine each other: neither is visible to the human eye until the two come together. Light and materials are mutually dependent on each other. Materials are key to understanding light in architecture because they directly affect the quantity and the quality of the light. Two qualities of materials – their finish and their color – are most important in this regard. There are many factor that effecting the lighting property, and I am discussing few of them which is most important.

Parallel lights cheat a little bit. They represent light that comes from an infinitely far away light source. Because of this, all of the light rays that reach the object are parallel. The standard use of parallel lights is to simulate the sun.

Point lights are one step better than directional lights. They represent infinitesimally small points that emit light. Light scatters out equally in all directions. Depending on how much effort we're willing to expend on the light, we can have the intensity falloff based on the inverse squared distance from the light, which is how real lights work.

Spotlights are the most expensive type of light, and should be avoided if possible because it is not for real time environment. We model a spotlight not unlike the type we would see in a theatrical production. They are point lights, but light only leaves the point in a particular direction, spreading out based on the aperture of the light.

It is the overall color of the object due to the global ambient light level. This is the color of the object when there's no particular light, just the general environmental illumination. That is, the ambient light is an approximation for the global illumination in the environment, and relies upon no light in the scene. It's usually a global value that's added to every object in a scene.

It is the color of the object due to the effect of a particular light. The diffuse light is the light of the surface if the surface were perfectly matte. The diffuse light is reflected in all directions from the surface and depends only on the angle of the light to the surface normal.

It is the color of the highlights on the surface. The specular light mimics the shininess of a surface, and its intensity is a function of the light's reflection angle off the surface. Specular materials, such as glossy finishes, reflect light as a mirror does, which can result in reflected images of the light source being visible ‘on’ the surface. Matte surfaces, such as natural stone, wood, and plaster, reflect light diffusely equally in all directions. Of the three aspects of color – hue, value, and intensity – value is the one that determines how much light is absorbed and how much is reflected.