US 4,928,250 A · System for deriving radiation images

Abstract

In an algorithm for deriving radiation images, where view independent radiation calculations are precomputed so that they do not need to be repeated for every view of the same environment. To find the form factors for radiosity techniques, a hemi-cube is constructed around the surface with grid cells defined for all faces on the hemi-cube. All other surfaces in the environment are projected onto the hemi-cube to facilitate the form factor calculations. A novel ray-tracing technique is disclosed where a light buffer in the form of a cube is constructed around each radiation source and grid cells are defined on the faces of the cube. Surfaces in the environment are projected onto the cube and the depths from the source are stored for each grid cell to facilitate shadow testing. Light reflected off of the viewed surface from another surface may be modeled by determining mirror positions of the viewer and the image plane. Instead of storing the depths of surfaces from the viewer or the radiation source, the identity of the polygons in the environment are stored instead to speed up the calculations. Scan conversion hardware is used to accelerate each of these operations. In a graphics pipeline, a feedback path is provided from the image processor to the CPU memory to store the result of the form factor or light buffer pre-computations to speed up the radiosity and ray-tracing calculations by several orders of magnitude.

Claims53

Dependent claims

A method for creating a radiation image of an environment from an observation location, said environment including a plurality of surfaces, wherein the radiation image of the environment is formed at least in part by radiation per unit area received by one surface from another surface, said radiation per unit area defining a form factor between the two surfaces, said method comprising:

defining a model of the surfaces and radiation sources in the environment;
defining and determining the radiation data of the environment, said data being substantially independent of the observation location, wherein said radiation data defining and determining step defines and determines form factors for diffusive radiation received by surfaces in the environment from other surfaces in the environment, and wherein said radiation data defining and determining step includes, for each pair of a first and a second surface in the environment;
(a) defining a hemi-polyhedron having a base plane substantially coplanar with the first surface and grid cells on each plane of the hemi-polyhedron;
and
(b) projecting an image of the second surface onto each said plane of the polyhedron as viewed from the first surface and determining the form factor;
performing perspective transformation of the environment relative to the observation location such that the radiation arriving at the location from the environment are substantially in parallel rays;
determining the surfaces or portions thereof from which radiation is observable at the location and the intensities of such radiation using the radiation data;
and
displaying the radiation image.

6 more elements

A method for determining the intensity of radiation observed at a location in an environment, said envriornment having at least one radiation source and two or more surfaces each represented by an identifier, wherein said method uses radiation data of the environment, said data having been defined by (a) defining a polyhedron enclosing said light source and defining grid cells on the planes of the polyhedron between the light source and the surfaces, (b) projecting images of said surfaces onto the polyhedron in the direction of the radiation source, and determining which grid cells are enclosed by or in contact with the images and the depth values defined as the distances or relative distances between said surfaces and the radiation source, and (c) storing the identifiers of said surfaces and their depth values as a record list for each such grid cell;

said method comprising:
(i) finding, on a surface by surface basis, which surfaces are closest to the location so that the radiation from these surfaces are observable at the location;
(ii) tracing a line from the observation location to a point on a surface to define an intersection point;
(iii) determining which grid cell intersects the line connecting the radiation source and the intersection point;
(iv) comparing the distance between the intersection point and the radiation source to the depth values in the record list for such grid cell to determine whether radiation from the source is interfered with by any surface in the environment when traveling towards the intersection point;
(v) computing the intensity of radiation reflected at or emitted by the intersection point towards the location;
and
(vi) repeating the steps (ii) through (v) for each of the surfaces and summing the intensities of radiation reflected at the intersection points to obtain the intensity of radiation observed at the location from the environment.

5 more elements

A method for determining the intensity of radiation observed at a location in an environment, said environment having at least one radiation source and two or more surfaces each represented by an identifier, wherein said method uses radiation data of the environment, said data having been defined by (a) defining a polyhedron enclosing said radiation source and defining grid cells on the planes of the polyhedron between the radiation source and the surfaces, (b) projecting images of said surfaces onto the polyhedron in the direction of the radiation source, and determining which grid cells are enclosed by or in contact with the images and the depth values defined as the distances or relative distances between said surfaces and the radiation source, and (c) storing the identifiers of said surfaces and their depth values as a record list for each such grid cell;

said method comprising:
(i) defining a picture plane having pixels therein with a predetermined size;
and
(ii) applying a scan conversion algorithm to determine which surfaces are closest to the location, and the pixels covered by each of the closest surface;
(iii) for each of the surfaces, tracing a line from the observation location to a predetermined point in a pixel covered by one of the surfaces and determining the intersection point between such line and said one surface to determine the intersection points on said one closest surface;
(iv) shadow testing each intersection point by determining which grid cell intersects the line connecting the radiation source and the intersection point, and by comparing the distance between the intersection point and the radiation source to the depth values in the record list for such grid cell to determine whether radiation from the source is interfered with by any surface in the environment when traveling towards the intersection point;
(v) computing, for at least some pixels, the intensity of radiation reflected at or emitted by each intersection point towards the location;
and
(vi) displaying the intensities of radiation computed for each pixel to produce the radiation image.

6 more elements

An apparatus for determining the intensity of radiation observed at a location in an environment, said environment having at least one radiation source and two or more surfaces each represented by an identifier, wherein said method uses radiation data of the environment, said data having been defined by (a) defining a polyhedron enclosing said light source and defining grid cells on the planes of the polyhedron between the light source and the surfaces, (b) projecting images of said surfaces onto the polyhedron in the direction of the radiation source, and determining which grid cells are enclosed by or in contact with the images and the depth values defined as the distances or relative distances between said surfaces and the radiation source, and (c) storing the identifiers of said surfaces and their depth values as a record list for each such grid cell;

said apparatus comprising:
(i) means for finding, on a surface by surface basis, which surfaces are closest to the location so that the radiation from these surfaces are observable at the location;
(ii) means for tracing a line from the observation location to a point on a surface to define an intersection point;
(iii) means for determining which grid cell intersects the line connecting the radiation source and the intersection point;
(iv) means for comparing the distance between the intersection point and the radiation source to the depth values in the record list for such grid cell to determine whether radiation from the source is interfered with by any surface in the environment when traveling towards the intersection point;
(v) means for computing the intensity of radiation reflected at or emitted by the intersection point towards the location;
and
(vi) means for summing the intensities of radiation reflected at the intersection points to obtain the intensity of radiation observed at the location from the environment.

5 more elements

said apparatus comprising:
(i) means for defining a picture plane having pixels therein with a predetermined size;
and
(ii) means for applying a scan conversion algorithm to determine which surfaces are closest to the location, and the pixels covered by each of the closest surface;
(iii) means for tracing, for each of the surfaces, a line from the observation location to a predetermined point in a pixel covered by one of the surfaces and determining the intersection point between such line and said one surface to determine the intersection points on said surface;
(iv) means for shadow testing each intersection point by determining which grid cell intersects the line connecting the radiation source and the intersection point, and by comparing the distance between the intersection point and the radiation source to the depth values in the record list for such grid cell to determine whether radiation from the source is interfered with by any surface in the environment when traveling towards the intersection point;
(v) means for computing, on a pixel by pixel basis, the intensity of radiation reflected at or emitted by each intersection point towards the location;
and
(vi) means for displaying the intensities of radiation computed for each pixel to produce the radiation image.

6 more elements

Dependencies are inferred from the claim text.

System for deriving radiation images

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System for deriving radiation images

Life of this patent

Abstract

Claims53