From 03a532db682d8bd1e2ef639a91f108576c690d88 Mon Sep 17 00:00:00 2001
From: Brandon Poythress <bgpoythress@yahoo.com>
Date: Sat, 19 May 2018 15:11:11 -0400
Subject: [PATCH] working on intersection

---
 Triangle.js             |   3 +
 lib/IntersectionMath.js | 137 ++++++++++++++++++++++++++++++++++++----
 2 files changed, 129 insertions(+), 11 deletions(-)
 create mode 100644 Triangle.js

diff --git a/Triangle.js b/Triangle.js
new file mode 100644
index 0000000..af61fc7
--- /dev/null
+++ b/Triangle.js
@@ -0,0 +1,3 @@
+function Triangle(point1, point2, point3){
+	
+}
\ No newline at end of file
diff --git a/lib/IntersectionMath.js b/lib/IntersectionMath.js
index 8726f7b..9f91cf5 100644
--- a/lib/IntersectionMath.js
+++ b/lib/IntersectionMath.js
@@ -1,13 +1,128 @@
 //find the intersection of a vector and a plane
-//pLX, pLY, pLZ are the components of the home point of the vector.
-//this will normally be the eye point but not necessarily.
+//linePointVector is the line point (Vector3 object)
 //u is a constant
-//dX, dY, dZ are the unit vector components of the line
-//pPX, pPY, pPZ are the components of the home point of the trianglular plane
-//nX, nY, nZ are the unit vector components of the triangle
-function getIntersection(pLX, pLY, pLZ, dX, dY, dZ, pPX, pPY, pPZ, nX, nY, nZ){
-	var crossProduct = crossProduct(dX, dY, dZ, nX, nY, nZ);
-
-	var point = [];
-	return point;
-}
\ No newline at end of file
+//dVector is the vector for the line (Vector3 object)
+//planePointVector is a point on the triangluar plane (Vector3 object)
+//nVector is the plane normal vecor (Vector3 object)
+function getIntersection(linePointVector, dVector, planePointVector, nVector){
+	
+	//calculate the cross product vector of the line vector and the 
+	//plane normal.  
+	var crossProduct = vector3CrossProduct(dVector, nVector);
+
+	//calculate the magnitude of that vector
+	var magnitude = vector3Magnitude(crossProduct);
+
+	//If the two are close to parallel, then it is a miss.
+	//if the are not parallel, it will be a hit and the intersection point
+	//will be calculated.
+	var e = 0.01;
+
+	if (mag < e){
+		return null;
+	} else{
+		var pMinusL = vector3Subtract(planePointVector, linePointVector);
+		var u = vector3DotProduct(pMinusL, nVector) / vector3DotProduct(dVector, nVector);
+
+		var intersect = vector3Add(linePointVector, vector3MultiplyByConst(u, dVector));
+
+		return intersect;
+	}
+
+}
+
+
+
+
+function vector3MultiplyByConst(constant, vector){
+	var i = vector.elements[0] * constant;
+	var j = vector.elements[1] * constant;
+	var k = vector.elements[2] * constant;
+
+	var result = new vector3();
+	result.elements[0] = i;
+	result.elements[1] = j;
+	result.elements[2] = k;
+
+	return result;
+}
+
+function vector3Add(startVector, addVector){
+	var i = startVector.elements[0] + addVector.elements[0];
+	var j = startVector.elements[1] + addVector.elements[1];
+	var k = startVector.elements[2] + addVector.elements[2];
+
+	var result = new Vector3();
+	result.elements[0] = i;
+	result.elements[1] = j;
+	result.elements[2] = k;
+
+	return result;
+}
+
+
+function vector3Subtract(startVector, minusVector){
+	var i = startVector.elements[0] - minusVector.elements[0];
+	var j = startVector.elements[1] - minusVector.elements[1];
+	var k = startVector.elements[2] - minusVector.elements[2];
+
+	var result = new Vector3();
+	result.elements[0] = i;
+	result.elements[1] = j;
+	result.elements[2] = k;
+
+	return result;
+}
+
+function vector3DotProduct(startVector, dotVector){
+	var iTerm = startVector.elements[0] * dotVector.element[0];
+	var jTerm = startVector.elements[1] * dotVector.element[1];
+	var kTerm = startVector.elements[2] * dotVector.element[2];
+
+	var result = iTerm + jTerm + kTerm;
+	return result;
+}
+
+function vector3CrossProduct(startVector, crossVector){
+	var a = startVector.elements;
+	var b = crossVector.elements;
+
+	var aX = a[0];
+	var aY = a[1];
+	var aZ = a[2];
+
+	var bX = b[0];
+	var bY = b[1];
+	var bZ = b[2];
+
+	var product = new Vector3();
+	var result = product.elements;
+
+	var cI = (aY*bZ) - (aZ*bY);
+	var cJ = (aZ*bX) - (aX*bZ);
+	var cK = (aX*bY) - (aY*bX);
+
+	result.push(cI);
+	result.push(cJ);
+	result.push(cK);
+
+	return product;
+}
+
+function vector3Magnitude(vector){
+	//the vector components
+	var a1 = vector.elements[0];
+	var a2 = vector.elements[1];
+	var a3 = vector.elements[2];
+
+	//the squares of each component
+	var b1 = Math.pow(a1, 2);
+	var b2 = Math.pow(a2, 2);
+	var b3 = Math.pow(a3, 2);
+
+	//the magnitude
+	var mag = Math.sqrt(b1 + b2 + b3);
+
+	return mag;
+}
+