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1 Curve Draw
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2 ==========
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3
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4 Overview
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5 --------
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6 Curvedraw is a simple 2D curve drawing program. I've often found it useful to
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7 draw curves for use in my graphics programs. They can be useful for procedural
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8 modelling (extrusion or surfaces of revolution), for animation paths, etc.
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9
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10 License
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11 -------
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12 Copyright (C) 2015 John Tsiombikas <nuclear@member.fsf.org>
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13 This program is free software. Feel free to use it, modify it and/or
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14 redistribute it under the terms of the GNU General Public License version 3 or
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15 (at your option) any later version published by the Free Software Foundation.
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16 See COPYING for details.
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17
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18 Usage
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19 -----
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20 Mouse:
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21 - Click to start adding points to a new curve, then finish it by right clicking.
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22 - Click on a curve to select it.
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23 - Right-click on a control point to remove it.
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24 - Click with a curve selcted to continue adding points to it.
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25 - Right-click in empty space to clear the selection.
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26
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27 Keys:
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28 - Holding 's' while adding points snaps to grid.
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29 - Holding SHIFT-'s' while adding points snaps to nearest existing point.
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30 - Press ESC to cancel the currently created curve.
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31 - Press 'q' to exit.
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32 - Press '1' - '3' to change selected curve type (polyline, hermite, bspline).
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33 - Press 'b' to show the selected curve's bounding box.
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34 - Press 'n' to normalize the selcted curve to the unit square.
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35 - Press 'e' to export the curves to a file called "test.curves" (TODO file dialog)
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36 - Press 'l' to load curves from the "test.curves" file (TODO file dialog)
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37
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38 Viewport:
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39 - Drag with the left or middle mouse button to pan.
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40 - Drag up or down with the right mouse button to zoom.
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41
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42 Curves file format
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43 ------------------
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44 The files read and written by this program are simple text files. They start
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45 with the word "GCURVES" in caps in the first line, followed by a series of curve
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46 blocks of the form::
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47
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48 curve {
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49 type <curve type, can be "hermite", "polyline", or "bspline">
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50 cpcount <number of control points>
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51 cp <x> <y> <z> <w>
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52 ...
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53 }
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54
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55 The control points are 4-vectors to allow for representing 3D rational
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56 b-splines. Lower-dimensional curves should set 'w' to 1, and all other unused
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57 coordinates to 0. Rational 2D b-splines are represented as 3D splines on the z=0
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58 plane, so again 'w' acts as the weight.
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