US 5,490,241 A · Interactive computer graphics system for making precise drawings

Abstract

A computer-aided illustration system and method emulate the set of tools that are typically available to the traditional technical illustrator and also provide the user with the ability to easily create illustrations in various two-dimensional projections, including paraline and perspective projections. The techniques described include: (1) providing moving polar grids which restrict a drawing to a user-specified geometry; (2) combining arbitrary user-specified directional constraints with several types of gravity, in a manner which enables a user to easily create new objects in alignment with previously drawn objects; (3) interrelating constraint systems and geometries (as delineated in the polar grids) with gravity, thereby providing the user with an effortless way to create objects with complex geometric interdependencies; and (4) adapting tools from linear geometry to work in non-linear projection planes (paraline and perspective).

Claims22

Dependent claims

In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, a method for assisting the creation and editing of illustrations comprising the steps of:

selecting a geometric mode from a set of geometric modes, at least one of the geometric modes of said set of geometric modes being adapted to facilitate drawing in two dimensions a two-dimensional representation of a three-dimensional object;
displaying on said display a grid representing the selected geometric mode, the grid having an origin;
placing a control point at a position on the displayed grid, said position being a point on said grid nearest to the cursor;
and
moving automatically the grid origin to the placed control point.

2 more elements

In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, said cursor being suited for placing control points, a method for assisting a user in the creation and editing of illustrations comprising the steps of:

(a) providing the user with an ability to select a geometric mode from a set of geometric modes, and displaying a grid representing the selected geometric mode on the display device responsively to an exercise by the user of said selecting ability;
(b) providing the user with an ability to specify an arbitrary angle representing a directional constraint, and selecting said angle responsively to an exercise by the user of said specifying ability;
(c) setting a hit radius equal to a particular distance from said cursor;
(d) displaying on said display at least one object capable of being described by a plurality of control points;
and
(e) if a portion of said at least one object is located within the hit radius of the cursor,
testing said portion of said at least one object for a first point representing at least one of said plurality of control points located within said hit radius of said cursor, and if said first point is found, constraining a next control point to lie at a position corresponding to said first point;
if said first point is not found, testing said portion of said at least one object for a second point representing an intersection with at least one other object, said second point being located within said hit radius of said cursor, and if said second point is found, constraining a next control point to lie at a position corresponding to said second point;
if said second point is not found, testing said portion of said at least one object for a third point representing an intersection with a line passing through a point of origin and having a direction defined by said angle, said point of origin being the origin of the displayed grid if said geometric mode was selected, said third point being located within said hit radius of said cursor, and if said third point is found, constraining a next control point to lie at a position corresponding to said third point;
if said third point is not found, testing said portion of said at least one object for a fourth point representing an intersection with said grid, said fourth point being located within said hit radius of said cursor, and if said fourth point is found, constraining a next control point to lie at a position corresponding to said fourth point;
and
if said fourth point is not found, constraining a next control point to lie at a position corresponding to said at least one object that is closest to said cursor.

9 more elements

A computer-aided drawing system comprising:

a computer having a processor and a memory;
a display coupled to said computer for displaying illustrations to a user;
a cursor-control means for positioning a cursor on the display, said cursor being suited for placing control points;
means for optionally selecting a geometric mode from a set of geometric modes and displaying a grid representing the selected geometric mode on the display;
means for optionally selecting a user-specified angle representing a directional constraint;
means for setting a hit radius equal to a particular distance from said cursor;
means for displaying on said display at least one object capable of being described by a plurality of control points;
means, responsive to whether a portion of said at least one object is located within the hit radius of the cursor, for testing said portion of said at least one object for a first point representing at least one of said plurality of control points located within said hit radius of said cursor, and if said first point is found, constraining a next control point to lie at a position corresponding to said first point;
means, responsive to said first point's not being found, for testing said portion of said at least one object for a second point representing an intersection with at least one other object, said second point being located within said hit radius of said cursor, and if said second point is found, constraining a next control point to lie at a position corresponding to said second point;
means, responsive to said second point's not being found, for testing said portion of said at least one object for a third point representing an intersection with a line passing through a point of origin and having a direction defined by said directional constraint, said point of origin being the origin of the displayed grid if said geometric mode was selected, said third point being located within said hit radius of said cursor, and if said third point is found, constraining a next control point to lie at a position corresponding to said third point;
means, responsive to said third point's not being found, for testing said portion of said at least one object for a fourth point representing an intersection with said grid, said fourth point being located within said hit radius of said cursor, and if said fourth point is found, constraining a next control point to lie at a position corresponding to said fourth point;
and
means, responsive to said fourth point's not being found, for constraining a next control point to lie at a position corresponding to said at least one object that is closest to said cursor.

10 more elements

(a) providing the user with an ability to select a geometric mode from a set of geometric modes, and displaying a grid representing said selected geometric mode on the display device responsively to an exercise by the user of said selecting ability;
(b) providing the user with an ability to specify an angle representing a directional constraint, and selecting said angle responsively to an exercise by the user of said specifying ability;
(c) setting a hit radius equal to a particular distance from said cursor;
(d) if said angle is selected, constraining a next control point to lie at a position corresponding to the cursor on a line passing through the origin of the displayed grid and having a direction defined by the directional constraint;
(e) if a portion of at least one object capable of being described by a plurality of control points is displayed on said display within the hit radius of the cursor,
testing said portion of said at least one object for a first point representing at least one of said plurality of control points located within said hit radius of the cursor, and if said first point is found, constraining a next control point to lie at a position corresponding to said first point;
if said first point is not found, testing said portion of said at least one object for a second point representing an intersection with at least one other object, said second point being located within said hit radius of the cursor, and if said second point is found, constraining a next control point to lie at a position corresponding to said second point;
if said second point is not found, testing said portion of said at least one object for a third point representing an intersection with a line passing through a point of origin and having a direction defined by said directional constraint, said point of origin being the origin of the displayed grid if said geometric mode was selected, said third point being located within said hit radius of the cursor, and if said third point is found, constraining a next control point to lie at a position corresponding to said third point;
if said third point is not found, testing said portion of said at least one object for a fourth point representing an intersection with said grid, said fourth point being located within said hit radius of the cursor, and if said fourth point is found, constraining a next control point to lie at a position corresponding to said fourth point;
and
if said fourth point is not found, constraining a next control point to lie at a position corresponding to said at least one object that is closest to said cursor;
(f) if said at least one object is not displayed within the hit radius of the cursor and said geometric mode is selected, placing a next control point corresponding to a position on said grid, said position being a point on said grid nearest to the cursor;
and
(g) if said geometric mode is not selected, placing a next control point corresponding to the cursor.

11 more elements

Dependencies are inferred from the claim text.

Interactive computer graphics system for making precise drawings

Life of this patent

Interactive computer graphics system for making precise drawings

Life of this patent

Abstract

Claims22