1 #define __PERSPECTIVE_LINE_C__
3 /*
4 * Perspective line for 3D perspectives
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 "perspective-line.h"
15 #include "desktop.h"
17 namespace Box3D {
19 PerspectiveLine::PerspectiveLine (NR::Point const &pt, Box3D::Axis const axis, Perspective3D *perspective) :
20 Line (pt, *(perspective->get_vanishing_point(axis)), true)
21 {
22 g_assert (perspective != NULL);
23 g_assert (Box3D::is_single_axis_direction (axis));
25 if (perspective->get_vanishing_point(axis)->state == VP_INFINITE) {
26 this->set_direction(perspective->get_vanishing_point(axis)->v_dir);
27 }
28 this->vp_dir = axis;
29 this->persp = perspective;
30 }
32 // This function makes sure not to return NR::Nothing()
33 // FIXME: How to gracefully handle parallel lines?
34 NR::Maybe<NR::Point> PerspectiveLine::intersect (Line const &line)
35 {
36 NR::Maybe<NR::Point> pt = this->Line::intersect(line);
37 if (!pt) {
38 Box3D::VanishingPoint vp = *(persp->get_vanishing_point(vp_dir));
39 if (vp.state == VP_INFINITE) {
40 pt = vp;
41 } else {
42 pt = NR::Point (0.0, 0.0); // FIXME: Better solution needed
43 }
44 }
45 return pt;
46 }
48 // FIXME: Do we really need two intersection methods?
49 NR::Point PerspectiveLine::meet(Line const &line)
50 {
51 return *intersect(line); // works since intersect() does not return NR::Nothing()
52 }
54 NR::Point PerspectiveLine::pt_with_given_cross_ratio (NR::Point const &C, NR::Point const &D, double gamma)
55 {
56 if (persp->get_vanishing_point (vp_dir)->is_finite()) {
57 NR::Point V (*persp->get_vanishing_point (vp_dir));
58 return fourth_pt_with_given_cross_ratio (V, C, D, gamma);
59 } else {
60 if (fabs (gamma - 1) < epsilon) {
61 g_warning ("Cannot compute point with given cross ratio.\n");
62 return NR::Point (0.0, 0.0);
63 }
64 Line line (C, D);
65 double lambda_C = line.lambda (C);
66 double lambda_D = line.lambda (D);
67 return line.point_from_lambda ((lambda_D - gamma * lambda_C) / (1 - gamma));
68 }
69 }
71 NR::Maybe<NR::Point> PerspectiveLine::intersection_with_viewbox (SPDesktop *desktop)
72 {
73 NR::Rect vb = desktop->get_display_area();
74 /* remaining viewbox corners */
75 NR::Point ul (vb.min()[NR::X], vb.max()[NR::Y]);
76 NR::Point lr (vb.max()[NR::X], vb.min()[NR::Y]);
78 std::pair <NR::Point, NR::Point> e = side_of_intersection (vb.min(), lr, vb.max(), ul, this->pt, this->v_dir);
79 if (e.first == e.second) {
80 // perspective line lies outside the canvas
81 return NR::Nothing();
82 }
84 Line line (e.first, e.second);
85 return this->intersect (line);
86 }
88 } // namespace Box3D
90 /*
91 Local Variables:
92 mode:c++
93 c-file-style:"stroustrup"
94 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
95 indent-tabs-mode:nil
96 fill-column:99
97 End:
98 */
99 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :