Compared to the directional light, point lights may only cover parts of the screen. In addition, it may be partially or fully occluded by the scene as viewed when generating the GBuffer. Fortunately, all we need to represent the light source volume is to render the front of a sphere located at the point light's center position and scale to its range.

Representing the light source as its volume makes sense when you think about the portion of the scene encapsulated by this volume. In the point lights case, the portion of the scene that gets lit is going to be inside this sphere volume. Rendering the volume will trigger the pixel shader for all pixels that are inside the volume, but could also trigger the pixel shader for pixels that are in front or behind the volume. Those pixels that are outside the volume will either get culled by the depth test or get fully attenuated so they won't affect the final image.

In the DirectX9 days you would normally use a pre-loaded mesh to represent...