Description of Interobject reflections

Interobject reflection effect on objects is one of the most important element for expressing smooth surface. For accelerate the rendering speed, we use approximation approach to calculate the effect. Therefore, rendered scene may have some kind of artifacts.

Our Algorithm is based on reflection mapping (also known as environment mapping). First, our renderer L2 creates infinity sphere surrounding cameras and all objects to be rendered. Second, the L2 maps a background picture on the sphere. Then the L2 calculates the direction of the reflecting area on the sphere of each surfaces of objects according to the camera location and the view direction. The reflection scenes on each specular surfaces are calculated in this way.

This algorithm do not care the interactions between objects, only considers the picture on the infinity sphere for reflection. When an object A is surrounded by other objects, the object A ignores other objects and reflects the scene on the infinity sphere only. For example, you create a house and you put a "most smooth" sphere. Even if you never see the outside of the house, the smooth sphere reflects the background scene on the infinity sphere surrounding the house.

On smooth objects, there will be occur a resemble situation described as "inconsistency between color and texture" in the section "Description of Texture". For instance, if blue sky is reflected with red object, what color will be made on the object? The answer is purple. This is the different result within the explanation of the section "Description of Texture".

In the case of specular reflection, reflected light will be added to the color of object�D In RGB color model, `R' element of red polygon has plus `R' value, blue sky has plus `B' value. Thus, compositing R and B color makes purple color. Therefore, color will be brighter only by specular reflection. This is totally opposite effect in the case of texture.

Especially, you should take care about the white object. The color white can not be bright anymore. Then, when you make the attribute of a white object "most smooth", no significant effect on the surface with reflection. (However, in the case of white object, shadow part of object may be dark and the effect of specular reflection can be seen in such area. If you want to emphasize the specular effect, set the object color gray and no texture on the object.

When you set an attribute of object smooth, and you set the background as `none' or `in space', the picture reflecting on objects may be black screen (or blank screen). Then the result will be the almost same situation with no specular effect.