From 8245fa75500a03bb5a814f332c9d5ef13411c075 Mon Sep 17 00:00:00 2001
From: Brandon Poythress <bgpoythress@yahoo.com>
Date: Sun, 20 May 2018 05:18:37 -0400
Subject: [PATCH] working on intersection

---
 Triangle.js | 78 +++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 70 insertions(+), 8 deletions(-)

diff --git a/Triangle.js b/Triangle.js
index 63ed9c0..7cb68d2 100644
--- a/Triangle.js
+++ b/Triangle.js
@@ -1,14 +1,76 @@
 
 //basic triangular building block.  takes in 
 //vector3 objects as the vertices
-function Triangle(point1In, point2In, point3In){
-	this.point1 = point1In;
-	this.point2 = point2In;
-	this.point3 = point3In;
+function Triangle(point0In, point1In, point2In){
+	this.point1 = point0In;
+	this.point2 = point1In;
+	this.point3 = point2In;
 
-	this.uVector = vector3Subtract(point2In, point1In);
-	this.vVector = vector3Subtract(point3In, point1In);
+	this.uVector = vector3Subtract(point1, point0);
+	this.vVector = vector3Subtract(point2, point0);
 
-	this.normalVector = vector3CrossProduct(uVector, vVector).normalize();
+	this.normalVector = vector3CrossProduct(this.uVector, this.vVector).normalize();
+
+	/*
+		a = (w dot u)(v dot v) - (w dot v)(u dot v) / 
+			(u dot u)(v dot v) - (u dot v)^2
+
+		b = (w dot v)(u dot u) - (w dot u)(u dot v) /
+			(u dot u)(v dot v) - (u dot v)^2
+
+		simplified to:
+
+		a = (w dot u)(v dot v) - (w dot v)(u dot v) / 
+			denominator
+
+		b = (w dot v)(u dot u) - (w dot u)(u dot v) /
+			denominator
+
+	*/
+
+	this.vDotV = vector3DotProduct(this.vVector, this.vVector);
+	this.uDotV = vector3DotProduct(this.uVector, this.vVector);
+	this.uDotU = vector3DotProduct(this.uVector, this.uVector);
+
+	this.denominator = (this.uDotU * this.vDotV) - Math.pow(this.uDotV, 2);
+
+
+}
+
+//the bad part of the Triangle class is that the user has to remember to call this
+//before using the vectors.  But after weighing the options within javascript,
+//it seems like the only way to go.
+Triangle.prototype.updateVectors = function(){
+	
+	this.uVector = vector3Subtract(point1, point0);
+	this.vVector = vector3Subtract(point2, point0);
+
+	this.normalVector = vector3CrossProduct(this.uVector, this.vVector).normalize();
+
+	this.vDotV = vector3DotProduct(this.vVector, this.vVector);
+	this.uDotV = vector3DotProduct(this.uVector, this.vVector);
+	this.uDotU = vector3DotProduct(this.uVector, this.uVector);
+
+	this.denominator = (this.uDotU * this.vDotV) - Math.pow(this.uDotV, 2);
+};
+
+Triangle.prototype.isHit = function(intersectionPoint){
+
+	var pointW = vector3Subtract(intersectionPoint, this.point0);
+	var wDotU = vector3DotProduct(pointW, this.uVector);
+	var wDotV = vector3DotProduct(pointW, this.vVector);
+
+	var a = ((wDotU * this.vDotV) - (wDotV * this.uDotV)) / this.denominator;
+	var b = ((wDotV * this.uDotU) - (wDotU * this.uDotV)) / this.denominator;
+
+
+
+	if(a >= 0.0005 && a <= 0.995 && b >= 0.0005 && b<=0.9995 && (a+b) <= 0.9995){
+		return true;
+	} else{
+		return false;
+	}
+
+
+};
 
-}
\ No newline at end of file