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Sub-Structuring Radiosity in Animation Environment

IP.com Disclosure Number: IPCOM000119291D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 111K

Publishing Venue

IBM

Related People

Doi, A: AUTHOR [+2]

Abstract

Disclosed is a high-speed radiosity method that reduces the computational cost without sacrificing image quality in animation environments with changing geometry or topology.

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This is the abbreviated version, containing approximately 52% of the total text.

Sub-Structuring Radiosity in Animation Environment

      Disclosed is a high-speed radiosity method that reduces
the computational cost without sacrificing image quality in animation
environments with changing geometry or topology.

      The radiosity method has become very popular, because it
produces very realistic images, and provides global illumination
effects. The basic radiosity procedure for image generation is based
on methods from thermal engineering and is good for environments
composed of ideal diffuse emitters and reflectors. The procedure
determines surface intensities for diffuse environments, and computes
form-factors, which represent the geometrical relationship between
any two surfaces based on the shape, area, and orientation of each
surface, the distance between them, and the portion of each patch
visible to the others.

      Computing the form-factors involves  a large computational
cost.  Several approaches have been formulated to reduce this expense
without sacrificing image quality. But they are still insufficient in
animation environments with changing geometry or topology.

      Previously, a full matrix radiosity method was needed to solve
the entire matrix equation as follows:
 Bi   =    piFij   Bi   +   Ei (1)
where   Bi  : Radiosity of patch-i
         pi  : Reflection of patch-i
         Fij : Form-factor of patch-i for patch-j
         Ei  : Emission radiosity of patch-i

      When the number of patches increases, the matrix of Equation
(1) becomes large and requires a lot of memory. Furthermore, when an
object is moved to a new place, the form-factors of all patches must
be calculated. In animation environments, this is too expensive.

      To solve these problems, we propose a sub-structuring radiosity
method. The new method focuses on space subdivision that divides an
object space into dynamic and static object spaces.  We introduce a
new concept, which we call interface.  Interface plays an important
role in the calculation of radiosity. We assume that interfaces
consist of transparent patches, and become the boundaries between
sub- spaces. They transmit radiosity between sub-spaces. By using
interface, we can divide the matrix of Equation (1) into smaller
matrices.

      We can solve Equation (1) by using interfaces as follows:
      B1       A1  0 H1  B1       E1
      B2   =    0 A2 H2  B2   +   E2 (2) B3       G1 G2 A3  B3
E3
where  B1  : Radiosity of static patch-i
        B2  : Radiosity of dynamic patch-i
        B3  : Radiosity of the interface bet...