package physicsSimulator;

import java.awt.*;

class Triangle extends Polygon {

public Triangle(Vector offset, Vector side1, Vector side2, Brush parent) {

this.offset = offset.clone(); //offset vector of the triangle's first point from the object's COM (will begin as relative to object's first point, gets updated when COM is calculated)

shape = new Vector[3];

shape[0] = (side1.clone());

shape[1] = (side2.clone());

shape[2] = (side1.plus(side2).mult(-1));

this.parent = parent;

this.length = 3;

}

public Vector centroid() {

return shape[0].plus(shape[2].mult(-1)).mult(1 / 3.0).plus(offset); //average of all three points (relative to shape's origin)

}

public double area() {

Vector A = shape[0];

Vector B = shape[2].mult(-1);

return 0.5 * Math.abs(A.x * B.y - B.x * A.y); // 1/2 * the determinant, apparently

}

public boolean contains(Vector point) { //make sure point is relative the the triangle's first point! (since the triangle doesn't know where it is relative to the origin)

Vector absA = parent.COM.plus(offset); //TODO: add private vars to cache values like this one for future calculations

Vector[] pointRel ={point.minus(absA), point.minus(absA.plus(shape[0])), point.minus(absA.minus(shape[2]))};

boolean sign = pointRel[0].leftOf(shape[0]);

for(int i=1; i<3; i++){

if(pointRel[i].leftOf(shape[i]) != sign)return false;

}

return true;

}

public void print() {

System.out.printf("[%f,%f]: [%f,%f], [%f,%f], [%f,%f]\n", offset.x, offset.y, shape[0].x, shape[0].y, shape[1].x, shape[1].y, shape[2].x, shape[2].y);

}

@Override

public void draw(Graphics g, Vector objectCOM) {

Vector pos = objectCOM.plus(offset);

for (Vector v : shape) {

v.draw(g, pos);

pos.add(v);

}

}

}