Method and apparatus for generating an elliptical image
First Claim
1. A method for generating data representative of an image of a world space model to be displayed on a screen, the model being defined by a plurality of features including at least one feature having an elliptical boundary, and the image being intended to present a view of the model from a predetermined eyepoint in world space wherein said method comprises the steps of:
- a. storing attribute data describing said at least one feature, the attribute data including two axes and an origin describing the major and minor axes of the elliptical boundary of said feature in world space coordinates, and a magnitude a and b representing the length of said major and minor axes;
b. transforming said attribute data from world space coordinates to eyepoint space coordinates;
c. determining the positions of a plurality of sampling points in screen space;
d. determining the position for each said sampling point of a point of intersection between a line drawn from the eyepoint through the sampling point and a plane defined by said two axes;
e. calculating the coordinates of each said point of intersection of the plane in a coordinate system defined by said two axes and said origin and calculating said coordinates in eyepoint space;
f. identifying each sampling point for which the respective coordinates lie within the elliptical boundary by calculating a vector offset for each said point of intersection of the plane from the origin, calculating components u, v of the calculated vector offset along the major and minor axes for each said point of intersection of the plane by using the vector dot products of the offset vector with each of the major and minor axes such that each point of intersection is considered to lie within the elliptical boundary if (u/a)2 +(v/b)2 <
=1; and
g. generating for each identified sampling point a sampling point output including attributes of said at least one feature.
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Accused Products
Abstract
Elliptical features are described in an image generator database in terms of an origin and major and minor axes defined by reference to a world or model space coordinate system. Image data is assembled for display by transforming the database contents into screen space and assessing for each of an array of sampling points distributed across screen space which features are to contribute to the portion of a final image in which the sampling point is located. In the case of elliptical features, data is transformed into eyepoint space and each sampling point is projected into eyepoint space to determine the point of intersection between a line drawn through the sampling point from the eyepoint and a plane defined by the axes. The coordinates of the intersection point in a coordinate system defined by the origin and axes, are used to determine whether or not the feature contributes to the sampling point.
43 Citations
8 Claims
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1. A method for generating data representative of an image of a world space model to be displayed on a screen, the model being defined by a plurality of features including at least one feature having an elliptical boundary, and the image being intended to present a view of the model from a predetermined eyepoint in world space wherein said method comprises the steps of:
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a. storing attribute data describing said at least one feature, the attribute data including two axes and an origin describing the major and minor axes of the elliptical boundary of said feature in world space coordinates, and a magnitude a and b representing the length of said major and minor axes; b. transforming said attribute data from world space coordinates to eyepoint space coordinates; c. determining the positions of a plurality of sampling points in screen space; d. determining the position for each said sampling point of a point of intersection between a line drawn from the eyepoint through the sampling point and a plane defined by said two axes; e. calculating the coordinates of each said point of intersection of the plane in a coordinate system defined by said two axes and said origin and calculating said coordinates in eyepoint space; f. identifying each sampling point for which the respective coordinates lie within the elliptical boundary by calculating a vector offset for each said point of intersection of the plane from the origin, calculating components u, v of the calculated vector offset along the major and minor axes for each said point of intersection of the plane by using the vector dot products of the offset vector with each of the major and minor axes such that each point of intersection is considered to lie within the elliptical boundary if (u/a)2 +(v/b)2 <
=1; andg. generating for each identified sampling point a sampling point output including attributes of said at least one feature. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An image generator for generating data representative of an image of a world space model to be displayed on a screen, the model being defined by a plurality of features including at least one feature having an elliptical boundary, and the image being intended to present a view of the model from a predetermined eyepoint in world space, wherein the image generator comprises:
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a. means for storing attribute data describing said at least one feature, the attribute data including two axes and an origin which describe the major and minor axes of the elliptical boundary of said feature in world space coordinates, and a magnitude a and b representing the length of said major and minor axes; b. means for retrieving said attribute data from said storage means and transforming said attribute data from world space coordinates to eyepoint space coordinates; c. means for determining the positions of a plurality of sampling points in screen space; d. means for determining the position for each said sampling point of a point of intersection between a line drawn from the eyepoint through the sampling point and a plane defined by said two axes; e. means for calculating the coordinates of each said point of intersection of said plane in a coordinate system defined by said two axes and said origin and calculating said coordinates in eyepoint space; f. means for identifying each sampling point for which the respective coordinates lie within the elliptical boundary by calculating a vector offset for each said point of intersection of the plane from the origin, calculating components u, v of the calculated vector offset along the major and minor axes for each said point of intersection of the plane by using the vector dot products of the offset vector with each of the major and minor axes such that each point of intersection is considered to lie within the elliptical boundary if (u/a)2 +(v/b)2 <
=1; andg. means for generating for each identified sampling point a sampling point output including attributes of said at least one feature.
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Specification