/// Distance between point p and line segment p1, p2
static double distance(math::vec3 const& p, math::vec3 const& p1, math::vec3 const& p2)
{
math::vec3 const v = p2 - p1;
math::vec3 const w = p - p1;
double const c1 = w.dot(v);
double const c2 = v.dot(v);
double const b = c1 / c2;
math::vec3 const pb = p1 + v * b;
return p.distance(pb);
}
static bool segment_plane_intersect(math::vec3 const& segment_point1, math::vec3 const& segment_point2,
math::vec3 const& plane_p0, math::vec3 const& plane_n, math::vec3& result)
{
math::vec3 const dir = (segment_point2 - segment_point1).normalize(); // ray direction
double const denom = plane_n.dot(dir);
if (math::is_zero(denom))
{
return false; // no intersection: ray is parallel to plane
}
math::vec3 const p1 = plane_p0 - segment_point1;
double const d = p1.dot(plane_n) / denom;
result = segment_point1 + dir * d; // intersection point
return true;
}
static bool segment_sphere_intersect(math::vec3 const& segment_point1, math::vec3 const& segment_point2,
math::vec3 const& sphere_center, double sphere_radius)
{
#if 0
math::vec3 closest_point;
closest_point.get_nearest_point_on_line(sphere_center, segment_point1, segment_point2);
math::vec3 const distance = closest_point - sphere_center;
double const sqr_distance = distance.dot(distance);
double const sqr_radius = sphere_radius * sphere_radius;
return sqr_distance <= sqr_radius;
#else
math::vec3 const p = segment_point1 - sphere_center; // ray_origin - sphere_center
math::vec3 const d = (segment_point2 - segment_point1).normalize(); // ray_direction
double const a = d.dot(d);
double const b = 2 * d.dot(p);
double const c = p.dot(p) - sphere_radius * sphere_radius;
double const D = b * b - 4 * a * c;
if (D >= 0)
{
/*
intersection points:
double t[2];
t[0] = (-b - sqrt(D)) / (2 * a);
t[1] = (-b + sqrt(D)) / (2 * a);
math::vec3 result[2];
result[0] = segment_point1 + d * t[0];
result[1] = segment_point1 + d * t[1];
*/
return true;
}
return false;
#endif
}
