1 Curve Draw

2 ==========

3

4 Overview

5 --------

6 Curvedraw is a simple 2D curve drawing program. I've often found it useful to

7 draw curves for use in my graphics programs. They can be useful for procedural

8 modelling (extrusion or surfaces of revolution), for animation paths, etc.

9

10 License

11 -------

12 Copyright (C) 2015 John Tsiombikas <nuclear@member.fsf.org>

13 This program is free software. Feel free to use it, modify it and/or

14 redistribute it under the terms of the GNU General Public License version 3 or

15 (at your option) any later version published by the Free Software Foundation.

16 See COPYING for details.

17

18 Usage

19 -----

20 Mouse:

21 - Click to start adding points to a new curve, then finish it by right clicking.

22 - Click on a curve to select it.

23 - Right-click on a control point to remove it.

24 - Click with a curve selcted to continue adding points to it.

25 - Right-click in empty space to clear the selection.

26

27 Keys:

28 - Holding 's' while adding points snaps to grid.

29 - Holding SHIFT-'s' while adding points snaps to nearest existing point.

30 - Press ESC to cancel the currently created curve.

31 - Press 'q' to exit.

32 - Press '1' - '3' to change selected curve type (polyline, hermite, bspline).

33 - Press 'b' to show the selected curve's bounding box.

34 - Press 'n' to normalize the selcted curve to the unit square.

35 - Press 'e' to export the curves to a file called "test.curves" (TODO file dialog)

36 - Press 'l' to load curves from the "test.curves" file (TODO file dialog)

37

38 Viewport:

39 - Drag with the left or middle mouse button to pan.

40 - Drag up or down with the right mouse button to zoom.

41

42 Curves file format

43 ------------------

44 The files read and written by this program are simple text files. They start

45 with the word "GCURVES" in caps in the first line, followed by a series of curve

46 blocks of the form::

47

48 curve {

49 type <curve type, can be "hermite", "polyline", or "bspline">

50 cpcount <number of control points>

51 cp <x> <y> <z> <w>

52 ...

53 }

54

55 The control points are 4-vectors to allow for representing 3D rational

56 b-splines. Lower-dimensional curves should set 'w' to 1, and all other unused

57 coordinates to 0. Rational 2D b-splines are represented as 3D splines on the z=0

58 plane, so again 'w' acts as the weight.