Sphere mapping

In computer graphics, sphere mapping (or spherical environment mapping) is a parameterization of directional radiance obtained by projecting the reflection of a mirrored sphere onto a plane using an orthographic projection. The resulting 2D texture encodes incident light as a function of direction and is used for reflection mapping by converting a surface reflection vector into texture coordinates. The method assumes the environment is distant (so radiance depends only on direction), but it introduces non-uniform distortion and contains a singularity in the direction opposite the viewing direction used to create the map.

To use this data, the surface normal of the object, view direction from the object to the camera, and/or reflected direction from the object to the environment is used to calculate a texture coordinate to look up in the aforementioned texture map. The result appears like the environment is reflected in the surface of the object that is being rendered.