project_point_on_plane()

double project_point_on_plane	(	POINT3DZ *	p,
		PLANE3D *	pl,
		POINT3DZ *	p0
	)

Finds a point on a plane from where the original point is perpendicular to the plane.

Definition at line 1531 of file measures3d.c.

{
        /*In our plane definition we have a point on the plane and a normal vector (pl.pv), perpendicular to the plane
        this vector will be parallel to the line between our inputted point above the plane and the point we are
        searching for on the plane. So, we already have a direction from p to find p0, but we don't know the distance.
        */
 
        VECTOR3D v1;
        double f;
 
        if (!get_3dvector_from_points(&(pl->pop), p, &v1))
                return 0.0;
 
        f = DOT(pl->pv, v1);
        if (FP_IS_ZERO(f))
        {
                /* Point is in the plane */
                *p0 = *p;
                return 0;
        }
 
        f = -f / DOT(pl->pv, pl->pv);
 
        p0->x = p->x + pl->pv.x * f;
        p0->y = p->y + pl->pv.y * f;
        p0->z = p->z + pl->pv.z * f;
 
        return f;
}

References DOT, FP_IS_ZERO, get_3dvector_from_points(), PLANE3D::pop, PLANE3D::pv, POINT3DZ::x, VECTOR3D::x, POINT3DZ::y, VECTOR3D::y, POINT3DZ::z, and VECTOR3D::z.

Referenced by lw_dist3d_point_poly(), lw_dist3d_point_tri(), lw_dist3d_ptarray_poly(), and lw_dist3d_ptarray_tri().

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