US 6,476,813 B1 · Method and apparatus for preparing a perspective view of an approximately spherical surface portion

Abstract

A computer system (10) can prepare and present on a display (22) a two-dimensional image that includes a perspective view, from a selected eyepoint (71, 152), of an object (23) which is a three-dimensional object of an approximately spherical shape, such as the earth. The system maintains image information for the object at each of several different resolution levels, portions of which are selected and mapped into the perspective view for respective portions of the surface of the object. In order to determine what resolution level to use for a given section of the surface of the object, the system relies on a combination of a logarithm of the square of a distance from the eyepoint to a point on the surface section, and a logarithm of the square of the degree of tilt of the surface section in relation to the eyepoint. In order to determine how far to conceptually tessellate or subdivide the surface of the object, the system relies on the logarithm of the square of the distance from the eyepoint to the point on the surface section.

Claims24

Dependent claims

A method for preparing a perspective view relative to an eyepoint of a surface section having an approximately spherical curvature, the method comprising:

maintaining a database that includes a plurality of sets of image data which each include a representation of the surface section at a respective one of a plurality of different resolutions;
subdividing the surface section into a plurality of subsections;
selecting one of the plurality of subsections;
determining a resolution value and a tessellation value at each of a plurality of vertices of the selected subsection;
determining whether the resolution values fall within a predetermined range;
determining whether any tessellation value exceeds a threshold level;
selecting from the database for the selected subsection of the surface section one of the resolutions from which to extract an image information portion for that subsection in response to either the resolution values falling within a predetermined range or at least one tessellation value exceeding a threshold level;
and
mapping into the perspective view the selected image information portion for the selected subsection.

6 more elements

An apparatus, comprising a computer having a processor and a memory, said memory storing a database of image information which includes a plurality of sets of image data that each include a representation at a respective one of a plurality of different resolutions of a surface section having an approximately spherical curvature, and said memory storing program code executable by said processor, said processor being operable in response to execution of said program-code for preparing a perspective view of the surface section relative to an eyepoint, including:

subdividing said surface section into a plurality of subsections;
selecting from the database for each said subsection of said surface section one of said resolutions from which to extract an image information portion for that subsection;
and
mapping into the perspective view the selected image information portion for each said subsection;
wherein at least one of said subdividing and selecting operations is carried out without mathematical computation of at least one of trigonometric functions and exponential functions.

2 more elements

A computer program product for use in conjunction with a computer system, the computer program product comprising a computer readable storage medium and a computer program mechanism embedded therein, the computer program mechanism including:

a first program portion for establishing an eyepoint relative to a surface section which has an approximately spherical curvature, said eyepoint serving as a reference to facilitate preparation of a perspective view of said surface section;
a second program portion for subdividing said surface section into a plurality of subsections;
a third program portion for accessing a database containing a plurality of sets of image data that each include a representation of said surface section at a respective one of a plurality of different resolutions;
and
a fourth program portion for selecting from the database for each said subsection of said surface section one of said resolutions from which to extract an image information portion for that subsection;
wherein at least one of said subdividing and selecting steps is carried out without mathematical computation of at least one of trigonometric functions and exponential functions.

3 more elements

Dependencies are inferred from the claim text.

Method and apparatus for preparing a perspective view of an approximately spherical surface portion

Life of this patent

Method and apparatus for preparing a perspective view of an approximately spherical surface portion

Life of this patent

Abstract

Claims24