Mental ray Rendering engine----environment mapping

An environment map, sometimes referred to as reflection mapping, is a technique for using texture mapping on an infinity sphere or cube or similar closed body, and calculates the shape of an object that uses an environment map to reflect it. The closed form itself is not an object, it is only abstract, and only the analytical observation direction and observation position are calculated.

An environment map is a local effect, meaning that it is related only to objects that use environment mappings and not to other objects. In fact, the environment map is connected to the material using the environment mapping object, which means that two different objects can have different environment maps, and any object is like this. Environment mapping is a cheap choice for real reflection.

This is a ray-traced reflection of other objects in the scene, and the environment map does not reflect. And, unlike true reflections that require ray tracing, the calculation of the environment map is simple and fast.

Environment mapping is not a good way to simulate specular reflections or to accurately reflect other objects in a scene, but as long as a little bit of environmental mapping works, objects can be used to show a shiny effect. It is also useful when simulating high-curvature steel surfaces, because such surface reflections are highly distorted and accurate reflections on other objects do not matter. Connecting a smooth map to an object's environmental map makes the object shiny, and the calculation costs little.

Material phenomenon uses the mib_reflect shader to fuse the computed results of Mib_illum_phong shaders and environment maps. The reflectivity is constant, which can be controlled by the appropriate texture shader that is connected to the reflect parameter. Note that the environment itself is not part of the material phenomenon. A separate environment map connects to the material and provides a lookup function. This environment mapping is called local environment because they are applied only to the material on which they are connected. If a material is attached to an instance, the material inheritance is applied to other objects in the tree, and the texture map is used by other objects as well.

Mental ray Rendering engine----environment mapping