intersect_line_plane.hpp

#ifndef PASTELGEOMETRY_INTERSECT_LINE_PLANE_HPP
#define PASTELGEOMETRY_INTERSECT_LINE_PLANE_HPP

#include "pastel/geometry/intersect/intersect_line_plane.h"

#include "pastel/sys/mytypes.h"
#include "pastel/geometry/shape/line.h"
#include "pastel/geometry/shape/plane.h"

namespace Pastel
{

    template <typename Real, integer N>
        bool intersect(
            const Line<Real, N>& line,
            const Plane<Real, N>& plane,
            Real& t)
    {
        // Let
        // P = line point
        // D = line direction
        // S = plane point
        // N = plane normal
        //
        // R(t) = P + tD
        // dot(N, S - R(t)) = 0
        // =>
        // dot(N, S - P) - t * dot(N, D) = 0
        // =>
        // t = dot(N, S - P) / dot(N, D)
        //
        // If dot(N, D) == 0, then
        // the line and plane are parallel.

        Real n = dot(line.direction(), plane.normal());
        Real m = dot(plane.normal(), plane.position() - line.position());

        // EPSILON
        if (n == 0)
        {
            // EPSILON
            if (m == 0)
            {
                t = 0;
                return true;
            }
            return false;
        }

        t = m / n;

        return true;
    }

}

#endif