**Note**: The phi/theta direction in the video may be confusing, so please refer to the axis direction in the following figure. We will fix the video soon.
The final task of this assignment will be to implement a new type of light source: an infinite environment light. An environment light is a light that supplies incident radiance (really, the light intensity dPhi/dOmega) from all directions on the sphere. Rather than using a predefined collection of explicit lights, an environment light is a capture of the actual incoming light from some real-world scene; rendering using environment lighting can be quite striking.
The intensity of incoming light from each direction is defined by a texture map parameterized by phi and theta, as shown below.
