#define __PERSPECTIVE_LINE_C__

/*
 * Perspective line for 3D perspectives
 *
 * Authors:
 *   Maximilian Albert <Anhalter42@gmx.de>
 *
 * Copyright (C) 2007 authors
 *
 * Released under GNU GPL, read the file 'COPYING' for more information
 */

#include "perspective-line.h"
#include "desktop.h"

namespace Box3D {

PerspectiveLine::PerspectiveLine (NR::Point const &pt, Box3D::Axis const axis, Perspective3D *perspective) :
        Line (pt, *(perspective->get_vanishing_point(axis)), true)
{
    g_assert (perspective != NULL);
    g_assert (Box3D::is_single_axis_direction (axis));

    if (perspective->get_vanishing_point(axis)->state == VP_INFINITE) {
        this->set_direction(perspective->get_vanishing_point(axis)->v_dir);
    }
    this->vp_dir = axis;
    this->persp  = perspective;
}

// This function makes sure not to return NR::Nothing()
// FIXME: How to gracefully handle parallel lines?
NR::Maybe<NR::Point> PerspectiveLine::intersect (Line const &line)
{
    NR::Maybe<NR::Point> pt = this->Line::intersect(line);
    if (!pt) {
        Box3D::VanishingPoint vp = *(persp->get_vanishing_point(vp_dir));
        if (vp.state == VP_INFINITE) {
            pt = vp;
        } else {
            pt = NR::Point (0.0, 0.0); // FIXME: Better solution needed
        }
    }
    return pt; 
}

// FIXME: Do we really need two intersection methods?
NR::Point PerspectiveLine::meet(Line const &line)
{
    return *intersect(line); // works since intersect() does not return NR::Nothing()
}

NR::Point PerspectiveLine::pt_with_given_cross_ratio (NR::Point const &C, NR::Point const &D, double gamma)
{
    if (persp->get_vanishing_point (vp_dir)->is_finite()) {
        NR::Point V (*persp->get_vanishing_point (vp_dir));
        return fourth_pt_with_given_cross_ratio (V, C, D, gamma);
    } else {
        if (fabs (gamma - 1) < epsilon) {
            g_warning ("Cannot compute point with given cross ratio.\n");
            return NR::Point (0.0, 0.0);
        }
        Line line (C, D);
        double lambda_C = line.lambda (C);
        double lambda_D = line.lambda (D);
        return line.point_from_lambda ((lambda_D - gamma * lambda_C) / (1 - gamma));
    }
}

NR::Maybe<NR::Point> PerspectiveLine::intersection_with_viewbox (SPDesktop *desktop)
{
    NR::Rect vb = desktop->get_display_area();
    /* remaining viewbox corners */
    NR::Point ul (vb.min()[NR::X], vb.max()[NR::Y]);
    NR::Point lr (vb.max()[NR::X], vb.min()[NR::Y]);

    std::pair <NR::Point, NR::Point> e = side_of_intersection (vb.min(), lr, vb.max(), ul, this->pt, this->v_dir);
    if (e.first == e.second) {
        // perspective line lies outside the canvas
        return NR::Nothing();
    }

    Line line (e.first, e.second);
    return this->intersect (line);
}

} // namespace Box3D 
 
/*
  Local Variables:
  mode:c++
  c-file-style:"stroustrup"
  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
  indent-tabs-mode:nil
  fill-column:99
  End:
*/
// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :