Description:

Implicit Lambertian lighting involves randomly shooting rays out from the point where object is hit in order to find out how much direct light, on average, the object "gets" from light sources in the scene. A ray is shot from the eye to the object, and from there in some random direction. If the random ray hits a light, then the light contributed from that light is calculated as the emitted light for the object at that particular hit point. Since many random rays will miss all lights in the scene, many (I used 1000) samples per pixel must be used to generate smoothly lit images.

This image consists of a "light" in the shape of a sphere on top of a regular, non-emissive white sphere. Since the most random rays will hit the light from the top of the sphere, the top is whitest. The color of the bottom sphere gradually gets darker until no random rays hit the light and the bottom of the sphere matches the background color. This image was generated using 1024 samples per pixel with dimesions of 256x256 pixels. The emissiveness of the light is 2.0.

This image was generated using 25 samples per pixel with dimesions of 256x256 pixels. The emissiveness of the light is 2.0. Notice that with less samples per pixel, there are many more dark spots on the bottom sphere where the random ray didn't hit the light.

This image was generated using 1024 samples per pixel with dimesions of 256x256 pixels. The emissiveness of the light is 10.0.

This image was generated using 1024 samples per pixel with dimesions of 256x256 pixels. The emissiveness of the light is 10.0.

This image was generated using 512 samples per pixel with dimesions of 256x256 pixels. The emissiveness of the light is 10.0. The model used is happy_vrip.ply.