Question

I have a question regarding creating different types of light. What would be the difference between omnidirectional light and a light with a small cutoff angle, and what should I use in OpenGL to implement these.

Answer 1

The difference between omnidirectional and directional light models is the algorithm used to select which fragments are affected by the lights.

Omnidirectional lights affect all fragments is all directions, while directional light have a direction and a cut-off angle (the cone of light). Light commonly have a attenuation factors, used to limit the range of the application.

Usually lights contributes to fragment color by adding color components. Color components are ambient color, diffuse color, specular color… Each component is scaled with some parameter, such add the distance from the view point, or the angle of the reflected ray respect the view point (using eye-surface vectore and normal).

Using fixed pipeline (or compatibility profile), a state set is defined for enabling lighting. You can enable or disable a limited number of lights, set the light model and the model parameters. Light affect vertex color, not the fragment derived by vertex rasterization.

Using programmable pipeline, lights are defined by shader uniforms. Since shaders are programmable, you have to define your own lighting model using shader source.

The question is very wide.