1 package org.opentrafficsim.core.geometry;
2
3 import org.djutils.draw.point.Point2d;
4
5 /**
6 * Line representation that a {@code Flattener} can flatten in to a polyline.
7 * <p>
8 * Copyright (c) 2023-2024 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
9 * BSD-style license. See <a href="https://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
10 * </p>
11 * @author <a href="https://github.com/averbraeck">Alexander Verbraeck</a>
12 * @author <a href="https://tudelft.nl/staff/p.knoppers-1">Peter Knoppers</a>
13 * @author <a href="https://github.com/wjschakel">Wouter Schakel</a>
14 */
15 public interface FlattableLine
16 {
17
18 /**
19 * Returns the point at the given fraction. The fraction may represent any parameter, such as <i>t</i> in a Bezier, <i>s</i>
20 * in a Clothoid, or simply the fraction of length.
21 * @param fraction double; fraction.
22 * @return double; point at the given fraction.
23 */
24 Point2d get(double fraction);
25
26 /**
27 * Returns the direction at the given fraction. The fraction may represent any parameter, such as <i>t</i> in a Bezier,
28 * <i>s</i> in a Clothoid, or simply the fraction of length. The default implementation performs a numerical approach by
29 * looking at the direction between the points at fraction, and a point 1e-6 away.
30 * @param fraction double; fraction.
31 * @return double; direction at the given fraction.
32 */
33 default double getDirection(final double fraction)
34 {
35 Point2d p1, p2;
36 if (fraction < 0.5) // to prevent going above 1.0
37 {
38 p1 = get(fraction);
39 p2 = get(fraction + 1e-6);
40 }
41 else
42 {
43 p1 = get(fraction - 1e-6);
44 p2 = get(fraction);
45 }
46 return p1.directionTo(p2);
47 }
48
49 }