Browse Prior Art Database

Fast Pseudo-Radiosity Rendering using Function Approximation

IP.com Disclosure Number: IPCOM000118379D
Original Publication Date: 1997-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 156K

Publishing Venue

IBM

Related People

Aono, M: AUTHOR [+2]

Abstract

The disclosed method called Pseudo-Radiosity by Function Approximation (PRFA) allows a dynamic scene to be viewed from a dynamically changing viewpoint.

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Fast Pseudo-Radiosity Rendering using Function Approximation

      The disclosed method called Pseudo-Radiosity by Function
Approximation (PRFA) allows a dynamic scene to be viewed from a
dynamically changing viewpoint.

      The method employs function approximation from pre-computed
radiosity results to produce vertex colors of polygonal models.
Scenes may contain dynamic objects, i.e., objects that move or change
shapes, albeit with limited degrees of freedom.

      In the past, radiosity (1,2) processed scenes of significant
complexity were able to be displayed interactively with a
user-controlled, dynamically changing viewpoint.  An application
included "walkthrough" of realistically rendered architectural
models.  Such viewing relied on the fact that the (pure) radiosity
assumes all the reflection to be completely diffuse and thus the
surface intensity has no dependency on viewing direction.  A severe
limitation of this approach is that the scene is completely static,
in a sense that no objects could move nor change shape.

      Interactive viewing of dynamic scenes, in which objects move
and/or change shape, has been possible to some extent (for example,
(3,4)).  However, all efforts of this kind that achieved interactive
performance assumed a fixed viewpoint.  Those that allow arbitrary
viewpoint (5,6,7,8) has only been able to achieve speeds that are
far from interactive.

      The method described in this document, PRFA, allows interactive
viewing from an arbitrary viewpoint of a radiosity processed scene
that may contain objects that move and/or change shape.  Dynamic
viewpoint AND dynamic scene geometry have not been achieved at the
same time in the past; to the author's knowledge, the PRFA is the
first system to achieve both of these.  Note that the PRFA method has
limitation; most significantly, it has traded limited
Degrees-Of-Freedom (DOF) of the scene change for interactive viewing.
However, even with  such limitation, the PRFA method has many
potential applications. For  example, the method allows light sources
in so-called "virtual studio"  to move interactively.

      The PRFA method consists of the following steps (Figure).  Of
these, steps (1), (2), and (3) are performed as preprocess, while (4)
is performed interactively at rendering time.  For ease of
explanation, the DOF is assumed to be one.
  1.  Chose desired independent variable(s) for scene change.
       For example, the scene change could be a linear translation
       (1 DOF) or 2D translation (2 DOF) of a light source, or a
       degree of extension of a roll-down window screen (1 DOF).
       Here, as an example, we assume one DOF change in the scene
       with the variable x, which may be the position of a light
       source.
  2.  Discretely sample the (finite) domain of the independent
       variable(s), and compute radiositized scenes (which consists
      ...