// 3D Engine
//
// Triangle primative
//
// Stores triangle of vectors produced after transformation and associated colour.
//
// Author  Matthew Caryl
// Created 5.5.97

package ADT;

import java.awt.Color;
import java.awt.Graphics;

public class Triangle {
	//
	// Public interface
	//
	
	public Triangle(Vector V1, Vector V2, Vector V3, Vector normal, Color color) {
		v1 = V1; v2 = V2; v3 = V3;
		
		display_red = basic_red = color.getRed() / 255f;
		display_green = basic_green = color.getGreen() / 255f;
		display_blue = basic_blue = color.getBlue() / 255f;
		display_color = color;
		
		triangle_normal = normal;
		}
	
	public void light(Vector light) {
		NdotL = Math.min(1f, Math.max(0f, triangle_normal.dot(light)));
		}

	public boolean forwardFacing() {
		return v1.x * (v2.y - v3.y) + v2.x * (v3.y - v1.y) + v3.x * (v1.y - v2.y) > 0;
		}

	public boolean inFront() {
		return v1.z < 0 ||  v2.z < 0 ||  v3.z < 0;
		}
	
	public boolean aheadTriangle(Triangle triangle) {
		//return Math.max(v1.z, Math.max(v2.z, v3.z)) > Math.max(triangle.v1.z, Math.max(triangle.v2.z, triangle.v3.z));
		return (v1.z + v2.z + v3.z) > (triangle.v1.z + triangle.v2.z + triangle.v3.z);
		}
	
	public void draw(Graphics graphics, int[] xs, int[] ys, float ambient, float diffuse) {
		xs[0] = (int) v1.x; ys[0] = (int) v1.y;
		xs[1] = (int) v2.x; ys[1] = (int) v2.y;
		xs[2] = (int) v3.x; ys[2] = (int) v3.y;
		
		float d = diffuse * NdotL;
		float this_red = ambient * basic_red + d * basic_red;
		float this_green = ambient * basic_green + d * basic_green;
		float this_blue = ambient * basic_blue + d * basic_blue;
		
		if (this_red != display_red || this_green != display_green || this_blue != display_blue) {
			display_red = this_red; display_green = this_green; display_blue = this_blue;
			display_color = new Color(this_red, this_green, this_blue);
			}
		
		graphics.setColor(display_color);
		graphics.fillPolygon(xs, ys, 3);
		}
	
	//
	// Private interface
	//
	
	private Vector	v1, v2, v3;
	private Vector	triangle_normal;
	private float	NdotL;
	
	private float	basic_red, basic_green, basic_blue;
	private float	display_red, display_green, display_blue;
	private Color	display_color;
	}