Is a 4 poly emissive light slower than 4 poly parametric light?

vozolgant

Is a 4 poly emissive light slower than 4 poly parametric light? I keep hearing that parametric lights are faster than emissive lights. Can anyone confirm if this is true with objective evidence?

Tobor

The poly count is only one aspect for efficiency. Withonly four polys it's simpler ray tracing, so I wouldn't think there would be much differennce. Where there is a difference is how the lights are used. The standard spotlight and distant light (emissive mesh lights are also parametric) can produce more direct lighting, and it's the direct/nondirect lighting in a scene that most greatly affects rendering speed. The more the light rays are indirect the longer it will take.

If you were to do this test be sure to compare apples to apples. A spotlight set with a square emitter will more closely resemble the parameters of a mesh light with the same dimensions. The biggest difference between these two is that the mesh light will produce only diffuse lighting (assuming you don't use an IES profile). The spotlight can produce specular lighting, which in general is one of the elements that lends realism to a scene.