You can use a map for the background of a scene. Reflection maps and Refraction maps also use environment coordinates instead of texture coordinates.
While texture coordinates project a map onto particular geometry, environment coordinates project a map onto the world coordinate system. If you move the object, the map remains in place. If you move the point of view, the view of the map changes. This type of mapping system is used with reflection, refraction, and environment maps.
Above: Image uses a picture as a background. The environment map uses screen coordinates.
Below: Image shows a checkered map applied to the environment using spherical mapping coordinates.
There are four types of environment coordinates:
The first three are the same as those used by the UVW Map modifier. If you imagine a sphere, infinite in size, surrounding your scene and mapped with spherical mapping coordinates, you can visualize the effect you get with spherical environment mapping. Shrink-wrap wraps the map around a giant sphere, leaving only one singularity. Cylindrical is like a giant cylinder.
The Screen system maps the image directly to the view, with no distortion. It’s similar to planar projection, in that it's like a giant backdrop hung behind the scene. Unlike the other environment mapping methods, Screen is locked to the view. When you move the camera, the map moves with it. Therefore, you can use screen coordinates only for still renderings, or animations in which the camera doesn't move.
To use a bitmap with any environmental mapping system other than Screen, you need a high-resolution map because of the size of the virtual sphere or cylinder.
To assign an environment map as the background of the scene, use the Environment And Effects Dialog Environment panel.
To edit or adjust a map you assign by using the Environment And Effects dialog, you need to use the Material Editor. There are a few different ways to do so:
The map now appears in the sample slot, and you can use the rollouts below to edit its settings.