define_plane()

int define_plane	(	const POINTARRAY *	pa,
		PLANE3D *	pl
	)

Definition at line 1491 of file measures3d.c.

{
        const uint32_t POL_BREAKS = 3;
 
        assert(pa);
        assert(pa->npoints > 3);
        if (!pa)
                return LW_FALSE;
 
        uint32_t unique_points = pa->npoints - 1;
        uint32_t i;
 
        if (pa->npoints < 3)
                return LW_FALSE;
 
        /* Calculate the average point */
        pl->pop.x = 0.0;
        pl->pop.y = 0.0;
        pl->pop.z = 0.0;
        for (i = 0; i < unique_points; i++)
        {
                POINT3DZ p;
                getPoint3dz_p(pa, i, &p);
                pl->pop.x += p.x;
                pl->pop.y += p.y;
                pl->pop.z += p.z;
        }
 
        pl->pop.x /= unique_points;
        pl->pop.y /= unique_points;
        pl->pop.z /= unique_points;
 
        pl->pv.x = 0.0;
        pl->pv.y = 0.0;
        pl->pv.z = 0.0;
        for (i = 0; i < POL_BREAKS; i++)
        {
                POINT3DZ point1, point2;
                VECTOR3D v1, v2, vp;
                uint32_t n1, n2;
                n1 = i * unique_points / POL_BREAKS;
                n2 = n1 + unique_points / POL_BREAKS; /* May overflow back to the first / last point */
 
                if (n1 == n2)
                        continue;
 
                getPoint3dz_p(pa, n1, &point1);
                if (!get_3dvector_from_points(&pl->pop, &point1, &v1))
                        continue;
 
                getPoint3dz_p(pa, n2, &point2);
                if (!get_3dvector_from_points(&pl->pop, &point2, &v2))
                        continue;
 
                if (get_3dcross_product(&v1, &v2, &vp))
                {
                        /* If the cross product isn't zero these 3 points aren't collinear
                         * We divide by its lengthsq to normalize the additions */
                        double vl = vp.x * vp.x + vp.y * vp.y + vp.z * vp.z;
                        pl->pv.x += vp.x / vl;
                        pl->pv.y += vp.y / vl;
                        pl->pv.z += vp.z / vl;
                }
        }
 
        return (!FP_IS_ZERO(pl->pv.x) || !FP_IS_ZERO(pl->pv.y) || !FP_IS_ZERO(pl->pv.z));
}

References FP_IS_ZERO, get_3dcross_product(), get_3dvector_from_points(), getPoint3dz_p(), LW_FALSE, POINTARRAY::npoints, PLANE3D::pop, PLANE3D::pv, POINT3DZ::x, VECTOR3D::x, POINT3DZ::y, VECTOR3D::y, POINT3DZ::z, and VECTOR3D::z.

Referenced by lw_dist3d_line_poly(), lw_dist3d_line_tri(), lw_dist3d_point_poly(), lw_dist3d_point_tri(), lw_dist3d_poly_poly(), lw_dist3d_poly_tri(), and lw_dist3d_tri_tri().

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