US 6,549,205 B1Granted

Method of drawing shapes

AssigneeHitachi, Ltd.

InventorsYouichi Horii, Hiroyuki Nomura

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Abstract

In a system for producing an animation on a computer by use of keyframes, shapes are drawn on the basis of the positions of vertices designated by a user without direct manipulation of control points for Bézier curve so that there is little problem even in the case where a line drawing of each handwritten keyframe is broken discontinuously. To this end, Bézier curves are automatically generated to draw shapes by fetching a plurality of keyframes written on paper into a computer and then setting vertices of only first one of the keyframes. On this occasion, an optimum path connecting the position of each of the set vertices to the current cursor position is calculated. The path is approximated by a cubic equation. A Bézier curve is defined on the basis of comparison of coefficients of respective terms in the equation with coefficients in the Bézier curve. For each of keyframes after the first keyframe, control points for Bézier curve are re-calculated to reshape shapes by moving vertices of the previously drawn shapes and by dragging the neighborhood of the contour of the keyframe.

Claims2

Dependent claims

A method of drawing shapes, comprising:

(1) a first step in which, in order to trace, with Bézier curves, a contour of a first one of first and second keyframes stored in a memory on a computer, digitized as digital data and made consecutive to produce an animation, a Bézier curve between first and second vertices on the contour of said first keyframe is drawn when said second vertex is designated by use of a pointing device after said first vertex is designated, and above process is repeated between respective adjacent vertices on the contour of said first keyframe to thereby trace the contour of said first keyframe with Bézier curves;
(2) a second step in which said Bézier curves obtained by tracing the contour of said first keyframe are displayed on a display so that said Bézier curves are superimposed on said second keyframe;
and
(3) a third step in which, in a condition that said Bézier curves and said second keyframe are displayed on said display so that said Bézier curves are superimposed on said second keyframe, when a reshaping operation is performed manually by dragging said vertex by said pointing device in order to trace the contour of said second keyframe, and in the case where the position of each of vertices of said Bézier curves is judged to be anticoincident with the cursor position indicating the current position of said pointing device on said display while the button of said pointing device is pushed, a first train of points nearest to points on a locus of the cursor in a period between push and release of a button of said pointing device and darker than a predetermined threshold of brightness among a plurality of points constituting the contour of said second keyframe, and Bézier curves are calculated on the basis of said train of first points to regard said Bézier curves as a line drawing for tracing said second keyframe.

1 more element

Dependencies are inferred from the claim text.