https://en.wikipedia.org/wiki/Shading
Ambient Light:
has no source
is everywhere available
constant intensity
Diffuse Light:
has a direction
is scattered at the model surface
intensity depends on the angle between surface normal and incoming light direction
Specular Light:
has a direction
is reflected at the model surface
intensity depends on the angle between view direction and reflected light direction
vec3 Intensity(Diffuse) = Intensity(Light) * cos(N, -L)
vec3 Intensity(Specular) = Intensity(Light) * cos(R, -V) ^ Ns
vec3 N = Surface Normal
vec3 L = Light Direction
vec3 V = View Direction (Camera to Surface)
vec3 R = Reflected Light Direction
float Ns = Material(Shininess)
Note:
dot(A, B) = cos(A, B) * |A| * |B|
Light Equation:
vec3 FragmentColor(RGB) =
Intensity(Ambient) * Ka
+ TotalIntensity(Diffuse) * Kd
+ TotalIntensity(Specular) * Ks
vec3 Ka = Material(Ambient)
vec3 Kd = Material(Diffuse)
vec3 Ks = Material(Specular)
The ambient intensity in constant through the whole scene, but the diffuse and specular intensity must be accumulated for all light sources.
Material Properties:
vec3 Ka or "Material(Ambient)"
vec3 Kd or "Material(Diffuse)"
vec3 Ks or "Material(Specular)"
float Ns or "Shininess"
float d or "Transparency" (unused in light calculations)
Textures can be available
Types of Light Sources:
There are different types of light sources, each of them add a certain amount of light to the total diffuse and specular light, but NOT to the ambient part.
Directional Light:
has a constant direction
has constant intensity
example: sun light on earth's surface
Point Light:
has a position and a base intensity
has additional parameters for attenuation
intensity is distance-dependend: the bigger the distance between surface and point light, the weaker the intensity
example: candle or light bulb
Spot Light:
has a position and a base intensity as well as a middle direction
has an additional parameter for angle-dependend attenuation
the intensity depends not on the distance, but on the angle between middle direction and surface-to-light direction