[Quy Anh] «Elliot» Nguyen
97 lines
3.6 KiB
C++
97 lines
3.6 KiB
C++
#pragma once
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#include "vector2d.hpp"
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struct Obstacle {
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Vector2d start; // First endpoint of the obstacle segment.
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Vector2d end; // Second endpoint of the obstacle segment.
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Vector2d obstacle_v; // Direction vector of the segment: end - start.
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double length_sq_inv; // Inverse squared length of the segment, used for projection.
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// Default constructor: creates a degenerate obstacle at the origin.
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// This is mainly used for array allocation before assigning real obstacles.
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Obstacle() : start(0, 0), end(0, 0), obstacle_v(0, 0), length_sq_inv(0.0) {}
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// Constructs an obstacle as a finite line segment from s to e.
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//
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// The segment direction and inverse squared length are precomputed and cached because
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// they are reused when projecting pedestrian positions onto the obstacle.
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//
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// @param s The first endpoint of the obstacle segment.
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// @param e The second endpoint of the obstacle segment.
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//
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Obstacle(Vector2d s, Vector2d e) : start(s), end(e) {
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obstacle_v = end - start;
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double length_sq = obstacle_v.dot(obstacle_v);
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length_sq_inv = length_sq != 0.0 ? 1.0 / length_sq : 0.0;
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}
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// Flop count: 5 ADDs, 5 MULTs
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//
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// Finds the point on this finite obstacle segment that is closest to p.
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//
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// The method projects the vector (p - start) onto the obstacle direction
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// vector, then clamps the projection factor to [0, 1] so that the returned
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// point lies on the finite segment.
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//
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// Note : If the obstacle is a single point, meaning start == end, length_sq_inv is zero
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// and the method returns start.
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//
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// @param p The point for which the closest obstacle point is computed.
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// @return The closest point on the obstacle segment to p.
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//
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Vector2d find_nearest_obstacle_point(const Vector2d &p) const {
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// # 3 ADDs, 3 MULTs
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double projection = (p - start).dot(obstacle_v) * length_sq_inv;
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if (projection < 0.0)
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projection = 0.0;
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else if (projection > 1.0)
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projection = 1.0;
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// # 2 ADDs, 2 MULTs
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return start + obstacle_v * projection;
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}
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};
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struct Board {
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double length; // Board length.
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double width; // Board width.
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Obstacle *obstacles; // Array of obstacles contained in the board.
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int n_obstacles; // Total number of obstacles
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// Constructs a rectangular board of size length x width.
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//
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// The input array o contains n user-defined obstacles. The constructor copies
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// those obstacles and then appends the two horizontal borders of the board (bottom and top) as additional
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// obstacle segments:
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//
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// bottom: (0, 0) -> (length, 0)
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// top: (0, width) -> (length, width)
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//
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// Note: only the horizontal borders are modeled as obstacles. The vertical
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// borders are left open so pedestrians can enter and leave the walkway without
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// being affected by repulsive forces from those borders. This is consistent
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// with Fig. 2 in the paper, where the horizontal walkway boundaries are
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// emphasized but the vertical ends are not shown as walls.
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//
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// @param l The board length.
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// @param w The board width.
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// @param n The number of user-defined obstacles in o.
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// @param o Array of user-defined obstacles to copy into the board obstacles array.
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//
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Board(double l, double w, int n, Obstacle *o) : length(l), width(w), n_obstacles(n + 2) {
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obstacles = new Obstacle[n + 2];
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for (int i = 0; i < n; i++) {
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obstacles[i] = o[i];
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}
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// Board borders: bottom, top.
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obstacles[n] = Obstacle(Vector2d(0, 0), Vector2d(l, 0));
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obstacles[n + 1] = Obstacle(Vector2d(0, w), Vector2d(l, w));
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}
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// Releases the dynamically allocated obstacle array.
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~Board() { delete[] obstacles; }
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}; |