case TRACE_CONTOUR: {
			/* trace periphery - prioritize plane centers, more chance of hitting */
			VectorMA( box_origin, size[0]*0.5, x, p[k].pt ); k++;
			VectorMA( box_origin, -size[0]*0.5, x, p[k].pt ); k++;
			VectorMA( box_origin, size[1]*0.5, y, p[k].pt ); k++;
			VectorMA( box_origin, -size[0]*0.5, y, p[k].pt ); k++;
			VectorMA( box_origin, size[2]*0.5, z, p[k].pt ); k++;

			/* corners */
			VectorMA( box_origin, size[0]*0.5, x, p[k].pt );
			VectorMA( p[k].pt, size[2]*0.5, z, p[k].pt );
			k++;

			VectorMA( box_origin, -size[0]*0.5, x, p[k].pt );
			VectorMA( p[k].pt, size[2]*0.5, z, p[k].pt );
			k++;

			VectorMA( box_origin, size[1]*0.5, y, p[k].pt );
			VectorMA( p[k].pt, size[2]*0.5, z, p[k].pt );
			k++;

			VectorMA( box_origin, -size[1]*0.5, y, p[k].pt );
			VectorMA( p[k].pt, size[2]*0.5, z, p[k].pt );
			k++;

			break;
		}