1 #define __LINE_GEOMETRY_C__
3 /*
4 * Routines for dealing with lines (intersections, etc.)
5 *
6 * Authors:
7 * Maximilian Albert <Anhalter42@gmx.de>
8 *
9 * Copyright (C) 2007 authors
10 *
11 * Released under GNU GPL, read the file 'COPYING' for more information
12 */
14 #include "line-geometry.h"
15 #include "inkscape.h"
16 #include "desktop-style.h"
17 #include "desktop-handles.h"
18 #include "display/sp-canvas.h"
19 #include "display/sodipodi-ctrl.h"
20 //#include "display/curve.cpp"
22 namespace Box3D {
24 /**
25 * Draw a line beginning at 'start'. If is_endpoint is true, use 'vec' as the endpoint
26 * of the segment. Otherwise interpret it as the direction of the line.
27 * FIXME: Think of a better way to distinguish between the two constructors of lines.
28 */
29 Line::Line(NR::Point const &start, NR::Point const &vec, bool is_endpoint) {
30 pt = start;
31 if (is_endpoint)
32 v_dir = vec - start;
33 else
34 v_dir = vec;
35 normal = v_dir.ccw();
36 d0 = NR::dot(normal, pt);
37 }
39 Line::Line(Line const &line) {
40 pt = line.pt;
41 v_dir = line.v_dir;
42 normal = line.normal;
43 d0 = line.d0;
44 }
46 Line &Line::operator=(Line const &line) {
47 pt = line.pt;
48 v_dir = line.v_dir;
49 normal = line.normal;
50 d0 = line.d0;
52 return *this;
53 }
55 NR::Maybe<NR::Point> Line::intersect(Line const &line) {
56 NR::Coord denom = NR::dot(v_dir, line.normal);
57 g_return_val_if_fail(fabs(denom) > 1e-6, NR::Nothing());
59 NR::Coord lambda = (line.d0 - NR::dot(pt, line.normal)) / denom;
60 return pt + lambda * v_dir;
61 }
63 void Line::set_direction(NR::Point const &dir)
64 {
65 v_dir = dir;
66 normal = v_dir.ccw();
67 d0 = NR::dot(normal, pt);
68 }
70 NR::Point Line::closest_to(NR::Point const &pt)
71 {
72 /* return the intersection of this line with a perpendicular line passing through pt */
73 NR::Maybe<NR::Point> result = this->intersect(Line(pt, (this->v_dir).ccw(), false));
74 g_return_val_if_fail (result, NR::Point (0.0, 0.0));
75 return *result;
76 }
78 inline static double determinant (NR::Point const &a, NR::Point const &b)
79 {
80 return (a[NR::X] * b[NR::Y] - a[NR::Y] * b[NR::X]);
81 }
83 /* The coordinates of w with respect to the basis {v1, v2} */
84 std::pair<double, double> coordinates (NR::Point const &v1, NR::Point const &v2, NR::Point const &w)
85 {
86 double det = determinant (v1, v2);;
87 if (fabs (det) < epsilon) {
88 g_warning ("Vectors do not form a basis.\n");
89 return std::make_pair (0.0, 0.0);
90 }
92 double lambda1 = determinant (w, v2) / det;
93 double lambda2 = determinant (v1, w) / det;
94 return std::make_pair (lambda1, lambda2);
95 }
97 /* whether w lies inside the sector spanned by v1 and v2 */
98 bool lies_in_sector (NR::Point const &v1, NR::Point const &v2, NR::Point const &w)
99 {
100 std::pair<double, double> coords = coordinates (v1, v2, w);
101 return (coords.first >= 0 and coords.second >= 0);
102 }
104 static double pos_angle (NR::Point A, NR::Point B)
105 {
106 return fabs (NR::atan2 (A) - NR::atan2 (B));
107 }
109 /*
110 * Returns the two corners of the quadrangle A, B, C, D spanning the edge that is hit by a semiline
111 * starting at pt and going into direction dir.
112 * If none of the sides is hit, it returns a pair containing two identical points.
113 */
114 std::pair<NR::Point, NR::Point>
115 side_of_intersection (NR::Point const &A, NR::Point const &B, NR::Point const &C, NR::Point const &D,
116 NR::Point const &pt, NR::Point const &dir)
117 {
118 NR::Point dir_A (A - pt);
119 NR::Point dir_B (B - pt);
120 NR::Point dir_C (C - pt);
121 NR::Point dir_D (D - pt);
123 std::pair<NR::Point, NR::Point> result;
124 double angle = -1;
125 double tmp_angle;
127 if (lies_in_sector (dir_A, dir_B, dir)) {
128 result = std::make_pair (A, B);
129 angle = pos_angle (dir_A, dir_B);
130 }
131 if (lies_in_sector (dir_B, dir_C, dir)) {
132 tmp_angle = pos_angle (dir_B, dir_C);
133 if (tmp_angle > angle) {
134 angle = tmp_angle;
135 result = std::make_pair (B, C);
136 }
137 }
138 if (lies_in_sector (dir_C, dir_D, dir)) {
139 tmp_angle = pos_angle (dir_C, dir_D);
140 if (tmp_angle > angle) {
141 angle = tmp_angle;
142 result = std::make_pair (C, D);
143 }
144 }
145 if (lies_in_sector (dir_D, dir_A, dir)) {
146 tmp_angle = pos_angle (dir_D, dir_A);
147 if (tmp_angle > angle) {
148 angle = tmp_angle;
149 result = std::make_pair (D, A);
150 }
151 }
152 if (angle == -1) {
153 // no intersection found; return a pair containing two identical points
154 return std::make_pair (A, A);
155 } else {
156 return result;
157 }
158 }
160 void create_canvas_point(NR::Point const &pos, double size, guint32 rgba)
161 {
162 SPDesktop *desktop = inkscape_active_desktop();
163 SPCanvasItem * canvas_pt = sp_canvas_item_new(sp_desktop_controls(desktop), SP_TYPE_CTRL,
164 "size", size,
165 "filled", 1,
166 "fill_color", rgba,
167 "stroked", 1,
168 "stroke_color", 0x000000ff,
169 NULL);
170 SP_CTRL(canvas_pt)->moveto(pos);
171 }
173 void create_canvas_line(NR::Point const &p1, NR::Point const &p2, guint32 rgba)
174 {
175 SPDesktop *desktop = inkscape_active_desktop();
176 SPCanvasItem *line = sp_canvas_item_new(sp_desktop_controls(desktop),
177 SP_TYPE_CTRLLINE, NULL);
178 sp_ctrlline_set_coords(SP_CTRLLINE(line), p1, p2);
179 sp_ctrlline_set_rgba32 (SP_CTRLLINE(line), rgba);
180 sp_canvas_item_show (line);
181 }
183 } // namespace Box3D
185 /*
186 Local Variables:
187 mode:c++
188 c-file-style:"stroustrup"
189 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
190 indent-tabs-mode:nil
191 fill-column:99
192 End:
193 */
194 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :