Interactive computer graphics system for making precise drawings

Claim 3

A method as claimed in Claim 1, further comprising: placing a second control point (901) at a second position on the displayed grid, thereby defining a user-specifed angle; setting a lock angle equal to the user-specified angle; and constraining a next control point (907) to lie at a position on the lock angle nearest to the cursor (Fig. 9A to C).

Claim 8

A method as claimed in claim 4, in which said intersection is with another object, the method further comprising moving said cursor to a second position; placing a second control point at said second position, thereby defining a user-specified angle; setting a lock angle equal to the user-specified angle; and constraining a next control point to lie at a position on the lock angle nearest to the cursor.

Claim 11

A method as claimed in Claim 6, wherein said constraining step comprises: selecting a drawing mode for drawing a plurality of objects of a single type; placing at least one control point; and drawing on said selected face an object (1515) from said selected drawing mode.

Claim 12

A method as claimed in Claim 6, wherein said constraining step comprises: selecting an object on said display; selecting a transformation mode for transforming said selected object; placing at least one control point; and in response to said placed control point, effecting said selected transformation in said selected face on said selected object (Fig. 15E to G).

Claim 13

A computer-aided drawing system comprising: a computer having a memory (103) and a processor (101); a display device (105) coupled to said computer; a cursor-control device (107) coupled to said computer for moving a cursor (335) on said display device; means for selecting a geometric mode from the set of geometric modes (Fig. 2A to F; Fig. 3A to C) including linear, angular paraline, and perspective; means for displaying a grid representing the selected geometric mode on the display device, the grid having an origin; means for placing a control point at a position on the displayed grid nearest to the cursor; and means for moving the grid origin to the placed control point in response to said placing means.

Claim 14

A computer-aided drawing system comprising: a computer having a memory (103) and a processor (101); a display device (105) coupled to said computer; a cursor-control device (107) coupled to said computer for moving a cursor (335) on said display device; means for selecting a geometric mode from the set of geometric modes (Fig. 2A to F; Fig. 3A to C) including linear, angular paraline, and perspective; means for displaying a grid representing the selected geometric mode on the display device, the grid having an origin; means for placing a control point at a position on the displayed grid nearest to the cursor; and means for moving the grid origin to the placed control point in response to said placing means.

Claim 15

A computer-aided drawing system comprising: a computer having a processor (101) and a memory (103); a display (105) coupled to said computer for displaying illustrations to a user; a cursor-control means (107) for positioning a cursor (335) on the display, said cursor being suited for placing a plurality of control points. programming means (1701, 1703, 1705), coupled to said memory, for instructing said processor to perform the steps of: (a) if a geometry is desired by the user, selecting a geometric mode from a set of geometric modes representing said desired geometry, and displaying a grid representing the selected geometric mode on the display device; (b) if a user-specified angle is desired by the user, selecting a lock angle representing said desired angle; (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 said control points; (e) if said at least one object is located within the hit radius of the cursor, thereafter testing said at least object for a first point representing at least one of said control points located within said hit radius, and if said first point is found, constraining a next control point to lie at a position on said first point; if said first point is not found, testing said at least object for a second point representing an intersection with at least one other object, said second point being located within said hit radius, and if said second point is found, constraining a next control point to lie at a position on said second point; if said second point is not found, testing said at least object for a third point representing an intersection with said lock angle, said third point being located within said hit radius, and if said third point is found, constraining a next control point to lie at a position on said third point; if said third point is not found, testing said at least object for a fourth point representing an intersection with said grid, said fourth point being located within said hit radius, and if said fourth point is found, constraining a next control point to lie at a position on said fourth point, and if said fourth point is not found, constraining a next control point to lie at a position on said at least one object that is closest to said cursor.

Claim 16

A computer-aided drawing system comprising: a computer having a processor (101) and a memory (103); a display (105) coupled to said computer for displaying illustrations to a user; a cursor-control means (107) for positioning a cursor (335) on the display, said cursor being suited for placing a plurality of control points. programming means (1701, 1703, 1705), coupled to said memory, for instructing said processor to perform the steps of: (a) if a geometry is desired by the user, selecting a geometric mode from a set of geometric modes representing said desired geometry, and displaying a grid representing the selected geometric mode on the display device; (b) if a user-specified angle is desired by the user, selecting a lock angle representing said desired angle; (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 said control points; (e) if said at least one object is located within the hit radius of the cursor, thereafter testing said at least object for a first point representing at least one of said control points located within said hit radius, and if said first point is found, constraining a next control point to lie at a position on said first point; if said first point is not found, testing said at least object for a second point representing an intersection with at least one other object, said second point being located within said hit radius, and if said second point is found, constraining a next control point to lie at a position on said second point; if said second point is not found, testing said at least object for a third point representing an intersection with said lock angle, said third point being located within said hit radius, and if said third point is found, constraining a next control point to lie at a position on said third point; if said third point is not found, testing said at least object for a fourth point representing an intersection with said grid, said fourth point being located within said hit radius, and if said fourth point is found, constraining a next control point to lie at a position on said fourth point, and if said fourth point is not found, constraining a next control point to lie at a position on said at least one object that is closest to said cursor.