Cloth.java

package openmods.physics;

import com.google.common.collect.Lists;
import java.util.List;

public class Cloth {

	private List<Constraint> constraints = Lists.newArrayList();
	public Point[][] points;
	private double max_dim, spacing;
	private int num_x_points, num_y_points, n_constraints;

	private static final int PHYSICS_ITERATIONS = 2;

	public Cloth(int density, double width, double height) {
		this.max_dim = Math.max(width, height);
		Math.min(width, height);
		this.spacing = max_dim / density;
		this.num_x_points = (int)((density * (width / max_dim)) + 0.5);
		this.num_y_points = (int)((density * (height / max_dim)) + 0.5);

		int i, j;
		double x, y;
		points = new Point[num_y_points][];
		for (i = 0, y = 0; i < num_y_points; i++, y += spacing) {
			points[i] = new Point[num_x_points];
			for (j = 0, x = 0; j < num_x_points; j++, x += spacing) {
				points[i][j] = new Point(x / width, y / height, 0);

				if (i > 0) {
					this.constraints.add(new Constraint(this.points[i - 1][j], this.points[i][j], Double.NaN));
				}
				if (j > 0) {
					this.constraints.add(new Constraint(this.points[i][j - 1], this.points[i][j], Double.NaN));
				}
			}
		}

		this.points[0][0].inv_mass = 0;
		this.points[0][(num_x_points / 2)].inv_mass = 0;
		this.points[0][num_x_points - 1].inv_mass = 0;
		this.n_constraints = this.constraints.size();
	}

	public void update() {
		int num_x = this.num_x_points, num_y = this.num_y_points, num_c = this.n_constraints, num_i = PHYSICS_ITERATIONS, i, j;

		// Apply force ( Gravity )
		for (i = 0; i < num_y; i++) {
			for (j = 0; j < num_x; j++) {
				this.points[i][j].update();
			}
		}

		// Update constraints
		for (j = 0; j < num_i; j++) {
			for (i = 0; i < num_c; i++) {
				this.constraints.get(i).update();
			}
		}
	}

	public Point getClosestPoint(FastVector pos) {
		int num_x = this.num_x_points, num_y = this.num_y_points, i, j;
		double dist, min_dist = 1;
		Point min_point = null;

		for (i = 0; i < num_y; i++) {
			for (j = 0; j < num_x; j++) {
				dist = pos.subtract(this.points[i][j].getCurrent()).length();

				if (dist < min_dist) {
					min_dist = dist;
					min_point = this.points[i][j];
				}
			}
		}
		return min_point;
	}
}