Ground.java

package uk.co.flyingsquirrels.models;

import org.jbox2d.collision.PolygonDef;
import org.jbox2d.common.Vec2;
import org.jbox2d.dynamics.Body;
import org.jbox2d.dynamics.BodyDef;
import org.jbox2d.dynamics.World;

public class Ground {

	public Ground(World world, int worldWidth, int groundResolution,
			float maxGroundElevation, float minGroundElevation) {
		float heightMap[] = new float[worldWidth * 2 / groundResolution];
		populateHeightMap(maxGroundElevation, heightMap);

		for (int i = 0; i < heightMap.length - 1; i++) {
			BodyDef bodyDef = new BodyDef();
			Body ground = world.createBody(bodyDef);
			
			float x1 = -worldWidth + i * groundResolution;
			float x2 = x1 + groundResolution;
			float y1 = heightMap[i];
			float y2 = heightMap[i + 1];
			PolygonDef polygonDef = createPolygon(x1, x2, y1, y2, minGroundElevation);
			ground.createShape(polygonDef);
			
		}
	}

	private void populateHeightMap(float maxGroundElevation, float[] heightMap) {
		for (int i = 0; i < heightMap.length; i++) {
			heightMap[i] = maxGroundElevation - (float) Math.random()
					* maxGroundElevation;
		}
	}
	
	private PolygonDef createPolygon(float x1, float x2, float y1, float y2, float minY) {
		PolygonDef polygonDef = new PolygonDef();
		polygonDef.addVertex(new Vec2(x2, y2));
		polygonDef.addVertex(new Vec2(x1, y1));
		polygonDef.addVertex(new Vec2(x1, minY));
		polygonDef.addVertex(new Vec2(x2, minY));
		return polygonDef;
	}
	
}