Spotlights

Spotlights have color, position, and direction in which they emit light. Light emitted from a spotlight is made up of a bright inner cone, and a larger outer cone, with the light intensity diminishing between the two, as shown in the following illustration, along with the related members from the D3DLIGHT7 C++ structure (the D3DLIGHT7 Visual Basic type parallels this structure).

Spotlights are affected by falloff, attenuation, and range. These factors, as well as the distance light travels to each vertex, are figured in while computing lighting effects for objects in a scene. Computing all these effects for each vertex makes spotlights the most computationally expensive of all lights in Direct3D Immediate Mode.