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GLOBAL AMBIENT ILLUMINATION METHOD

IP.com Disclosure Number: IPCOM000008442D
Publication Date: 2002-Jun-13

Publishing Venue

The IP.com Prior Art Database

Abstract

The present invention relates generally to image processing, and more particularly to a method for enabling total diffuse illumination for an entire global illumination scene.

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GLOBAL AMBIENT ILLUMINATION METHOD

DESCRIPTION

Field of the Invention

The present invention relates generally to image processing, and more particularly to a method for enabling total diffuse illumination for an entire global illumination scene.

Background of the Invention

A complete rendered scene is made up of individual objects that are each illuminated based on various illumination parameters.  Without loss of generality reference will be made to one object and the results extended to all objects in the scene.  As shown in Figure 1c, if an object 104 is viewed in its natural surroundings 100 using a global light source such as the sun 102 or an overhead room light, the object 104 will appear with varying degree of illumination.  What is normally seen is a brightly lit region 104a for those surfaces that point directly to the light and the gradual decrease in brightness from that region.  The brightness decreases as a function of the angle that each surface makes with the global light source, e.g., the sun 102 or room light.  In a natural surrounding, the light bounces off all the surfaces 106 including the atmosphere, and lights up the back facing surface 104b as well.  In addition, other objects in a room such as ceilings, floors, and walls act as the reflectors of the light to make the object appear to be lit by multiple light sources.  The above described direct and indirect lighting acts as a global illumination.  The present invention concerns an efficient mechanism for producing this natural phenomena.

Global illumination refers to light that originates from the scene environment rather than from local interaction of the surface with direct illumination from the light source or sources.  In general, a light ray may reach the surface indirectly via reflection in other surfaces, transmission through partially transparent objects, or a combination of these.

As known to those skilled in the art of computer graphics and image processing, there are various lighting models which shade geometrically flat surfaces to make them appear as curved.  Phong and Gouraud models provides two such diffuse shadowing approaches.  In these models, however, only the interaction of surface points with direct illumination from light sources is considered.  For example, as shown in Figure 1a, the back facing portions 104b of the diffuse shading, i.e., the sides of objects which do not face the light source directly, are considered as not receiving any light source radiation.

A known solution to this problem is to provide one or more additional light sources that illuminate the backside of the object.  However, such a solution typically requires more lighting hardware or software processing time and can produce undesirable shading bands that move in an unnatural manner as the object or camera is moved in the scene.

Other exiting methods for producing global illumination in computer image processing include ray tracing and radiosity.  Although these methods can solve some o...