TriangleXYZ.java

package org.osm2world.core.math;

import java.util.List;

import com.google.common.collect.ImmutableList;

public class TriangleXYZ {

	public final VectorXYZ v1, v2, v3;

	public TriangleXYZ(VectorXYZ v1, VectorXYZ v2, VectorXYZ v3) {
		this.v1 = v1;
		this.v2 = v2;
		this.v3 = v3;
	}
	
	public List<VectorXYZ> getVertices() {
		return ImmutableList.of(v1, v2, v3);
	}
	
	/**
	 * returns the normalized normal vector of this triangle
	 */
	public VectorXYZ getNormal() {
		//TODO: account for clockwise vs. counterclockwise
		return v2.subtract(v1).crossNormalized(v2.subtract(v3));
	}

	public VectorXYZ getCenter() {
		return new VectorXYZ(
				(v1.x + v2.x + v3.x) / 3,
				(v1.y + v2.y + v3.y) / 3,
				(v1.z + v2.z + v3.z) / 3);
	}
	
	/**
	 * returns the triangle's y coord value at a {@link VectorXZ} within the
	 * triangle's 2D footprint.
	 * 
	 * It is obtained by linear interpolation within the triangle.
	 */
	public double getYAt(VectorXZ pos) {
		
		double a = v1.z * (v2.y - v3.y) + v2.z * (v3.y - v1.y) + v3.z * (v1.y - v2.y);
		double b = v1.y * (v2.x - v3.x) + v2.y * (v3.x - v1.x) + v3.y * (v1.x - v2.x);
		double c = v1.x * (v2.z - v3.z) + v2.x * (v3.z - v1.z) + v3.x * (v1.z - v2.z);
		double d = -a * v1.x - b * v1.z - c * v1.y;
		
		return -a/c * pos.x - b/c * pos.z - d/c;
		
	}
	
	@Override
	public String toString() {
		return "[" + v1.toString() + ", " + v2.toString() + ", " + v3.toString() + "]";
	}
	
}