For years I have seen people struggle with vector mathematics. This guide should walk you through the creation of a reusable Vector3
type in c# and the mathematics behind it all. The postfixed 3 simply refers to the vector being in 3dimensions (x,y,z).
The code is not designed to be fast or efficient but is to be as simple and understandable as possible. To this end, and as a personal preference, the Vector3 type is packed with relevent functionality and multiple interfaces to methods (e.g. static and nonstatic variants of methods). Many would deem this bloated code, however, I think that it makes the code programmer friendly. Obviously, as a projects grows I would tend to refactor functionality back out as I create objects and types for which the functions better fit. I see this as achieving maximum cohesion and minimising coupling and dependencies.
I have used the Cartesian coordinate system in threedimensions (i.e. three perpendicular axis of x, y and z) and Euclidian geometry. Don't worry about these terms; they are just the formal names for some of the maths covered at senior school. The vector space is volumetric (cube); note that you can use other vector spaces, such as a cylindrical space where one axis (usually z) relates to the radius of the cylinder.
You may have guessed that computers are quite slow with this type of math. Matrix mathematics is more efficient but much harder to understand. You will need a basic grasp of trigonometry and algebra to understand this guide.
Unless stated otherwise I assume that the vector is positional, originating at point (0,0,0). Alternatives to positional vectors are: unit vectors, which can be interpreted as either having no magnitude or an infinite magnitude; and vector pairs where the origin of the vector is another vector, magnitude being a distance from the origin vector.
Please note that this guide is extremely verbose and may seem patronising to experienced C# programmers. Please do not be offended, I have written the guide for a wide audience.
A quick glossary:
 Operator, this is the symbol used to define an operation such as plus (
+
) in (a+b)  Operand, these are the variables used in an operation such as (a) and (b) in (a+b). The lefthandside (LHS) operand is (a) where as the righthandside (RHS) operand is (b).
Using the code
To begin with, let us define how the vector information will be stored. I don't often create structs when coding, but for our Vector3
this is perfect. If you are reading this article you probably already know that a vector represents values along a number of axes. For this tutorial we will be developing a threedimensional type so... thee variables and three axis.
public struct Vector3
{
private readonly double x;
private readonly double y;
private readonly double z;
}
What orientation are the axes in? Being from a visualization background I always assume:
You may have noticed that Z is negative as you look down the axis. This is a common convention in graphics libraries such as OpenGL. This will become important later on when considering pitch, roll and yaw methods.
A quick diversion: Why a struct instead of a class?
The differences between struct and class:
 A struct is a value type created on the stack instead of the heap, thus reducing garbage collection overheads.
 They are passed by value not by reference.
 They are created and disposed of quickly and efficiently.
 You cannot derive other types from them (i.e. noninheritable).
 They are only appropriate for types with a small number of members (variables). Microsoft recommends a struct should be less than 16 bytes.
 You do not need the new keyword to instantiate a struct.
Basically, it looks like, acts like, and is a primitive type. Although, there is no reason why the vector type could not be created as a class. A drawback of developing a struct is that collection classes in the .NET framework cast structs as classes. This means that a large collection of Vector3
's will have a high casting overhead. Generic types were intoduced in C# v2.0 and can be used to reduce the performance cost of casting and boxing structs in collections.
A more indepth article on structs has been written by S. Senthil Kumar here
Accessing the variables
Did you notice that the variables were private and readonly?
While I have chosen to build a struct, I habitually hide my variables and create public accessor and mutator properties. This is not strictly good practice for structs, but I have created them in case I feel the need to convert to a class at a later date (this is good practice for class structures). In fact, in this type I will not be creating public mutators because a struct should be immutable.
The variables are readonly because this class will be immutable. The x, y, and z variables can only be set when the struct is being constructed. This means that once a Vector3
is built, it will always have the same value. All operations that are performed on the Vector3
will produce another struct. This is important because structs are passed by value which means that they are copied when passed to another method. If you change (or mutate) the values in another method then the changes are lost when you return to the calling method.
In addition to the properties, an array style interface has also been provided. This allows the user call the Vector3
with myVector[x]
, myVector[y]
, myVector[z]
. Additionally, the user can get all of the components as an array using the Array
property.
public double X
{
get{return this.x;}
}
public double Y
{
get{return this.y;}
}
public double Z
{
get{return this.z;}
}
public double[] Array
{
get{return new double[] {x,y,z};}
}
public double this[ int index ]
{
get
{
switch (index)
{
case 0: {return X; }
case 1: {return Y; }
case 2: {return Z; }
default: throw new ArgumentException(THREE_COMPONENTS, "index");
}
}
}
private const string THREE_COMPONENTS =
"Array must contain exactly three components, (x,y,z)";
A property has also been provided to access the magnitude of a vector. The magnitude (or absolute value) of a vector is its length , irrespective of direction and can be determined using the formula:
The SumComponentSquares
method (used below) can be seen later in this article.
public double Magnitude
{
get
{
return Math.Sqrt ( SumComponentSqrs() );
}
}
Constructing a Vector3
To construct the type using typical class syntax the following constructor methods have been provided:
public Vector3(double x, double y, double z)
{
this.x = x;
this.y = y;
this.z = z;
}
public Vector3 (double[] xyz)
{
if (xyz.Length == 3)
{
this.x = xyz[0];
this.y = xyz[1];
this.z = xyz[2];
}
else
{
throw new ArgumentException(THREE_COMPONENTS);
}
}
public Vector3(Vector3 v1)
{
this.x = v1.X;
this.y = v1.Y;
this.z = v1.Z;
}
private const string THREE_COMPONENTS =
"Array must contain exactly three components , (x,y,z)";
Operator overloading
We now have a framework for storing, accessing and mutating the Vector3
and its components (x,y,z). We can now consider mathematical operations applicable to a vector. Let's begin by overloading the basic mathematical operators.
Overloading operators allows the programmer to define how a type is used in the code. Take, for example, the plus operator (+
). For numeric types this would suggest addition of two numbers. For strings it represents the concatenation of two strings. Operator overloading is of huge benefit to programmers when describing how a type should interact with the system. In C# the following operators can be overloaded:
 Addition, concatenation, and reinforcement (
+
)  Subtraction and negation (

)  Logical negation (
!
)  Bitwise complement (
~
)  Increment (
++
)  Decrement (

)  Boolean Truth (
true
)  Boolean false (
false
)  Multiplication (
*
)  Division (
/
)  Division remainder (
%
)  Logical AND (
&
)  Logical OR (

)  Logical ExclusiveOR (
^
)  Binary shift left (
<<
)  Binary shift right (
>>
)  Equality operators, equal and notequal (
==
and !=
)  Difference\comparison operators, lessthan and greaterthan(
<
and >
)  Difference\comparison operators, lessthan or equalto and greaterthan or equalto(
<=
and >=
)
Quick Note: MSDN calls this operator overloading, however, what we are doing is more like operator overwriting. If the operators were defined on a base class then we would be using the term operator overwriting.
Addition (v3 = v1 + v2)
The addition of two vectors is achieved by simply adding the x, y, and z components of one vector to the other (i.e. x+x, y+y, z+z).
public static Vector3 operator+(Vector3 v1, Vector3 v2)
{
return new Vector3(
v1.X + v2.X,
v1.Y + v2.Y,
v1.Z + v2.Z);
}
Subtraction (v3 = v1  v2)
Subtraction of two vectors is simply the subtraction of the x, y, and z components of one vector from the other (i.e. xx, yy, zz).
public static Vector3 operator(Vector3 v1, Vector3 v2 )
{
return new Vector3(
v1.X  v2.X,
v1.Y  v2.Y,
v1.Z  v2.Z);
}
Negation (v2 = v1)
Negation of a vector inverts its direction. This is achieved by simply negating each of the component parts of the vector.
public static Vector3 operator(Vector3 v1)
{
return new Vector3(
v1.X,
v1.Y,
v1.Z);
}
Reinforcement (v2 = +v1)
Reinforcement of a vector actually does nothing but return the original vector given the rules of addition, (i.e. +x = x and ++x = +x).
public static Vector3 operator+(Vector3 v1)
{
return new Vector3(
+v1.X,
+v1.Y,
+v1.Z);
}
Other Overloaded Operators
Overloads for the following operators can be found elsewhere in the article:
Comparison
When checking for equality we examine the component parts (x,y,z) of the vectors. When comparing two vectors we compare the magnitude.
Comparing doubles (the magnitude or the component parts of the vector) seems strait forward, the .Net double type provides operators <, >, <=, >=, ==, != and implements IComparable and IEquatable. However, these operations are not reliable. This is because of the way that fractional numbers (i.e. float, double, and decimal variables) are stored in binary representation and the error margin of calculations on them. This gets more complicated when you try to account for special cases numbers: positive and negative 0, positive and negative infinity and NotANumber. See Bruce Dawson's article for more information.
There has been a lot of discussion in the comments of this article regarding the use of a threshold when calculating equality. I personally agree with red Baron who suggests that the end user should be responsible for tolerance as it relates to their application:
"... you should not implement a tolerance value inside your code.
What is a suitable value for this tolerance?
It is depending on the problem ..."
Operator signatures cannot be overloaded to take additional parameters so Vector3
's comparison operators will remain as intolerant as the double type's operators. When making a comparison between vectors it is recommended that you use <
, <=
, >
, >=
with a reasonable tolerance related to the end user application. This is in preference to equality operators ==
, !=
and .Equals
. The Equals method, however, can be overloaded.
There are a number of approaches to tolerant comparisons, those described in Bruce Dawson's article are:
 Epsilon comparison / Absolute error tolerance
Best suited for numbers close to 0  Relative epsilon comparison / Relative error tolerance
Best suited for numbers larger than 0 but difficult to define an appropriate value  Ulp (Units in the Last Place)
Best suited for numbers larger than 0
For the purposes of this article, only absolute error tolerance has been implemented and only as overloads where appropriate. It is important to remember that the operators (<, >, <=, >=, ==, !=) will not accept a tolerance value.
Lessthan (result = v1 < v2)
Lessthan compares two vectors, returning true only if the magnitude of the lefthandside vector (v1) is less than the magnitude of the other (v2). To improve efficiency, we do not need to take the final step when calculating the magnitude of a vector, which is to square root the result. The comparison will be the same for the magnitude squared.
public static bool operator<(Vector3 v1, Vector3 v2)
{
return v1.SumComponentSqrs() < v2.SumComponentSqrs();
}
Lessthan or Equalto (result = v1 <= v2)
Lessthan or equalto compares two vectors returning true only if the magnitude of the lefthandside vector (v1) is less than the magnitude of the other (v2) or the two magnitudes are equal. Again we use the squared magnitude for efficiency.
public static bool operator<=(Vector3 v1, Vector3 v2)
{
return v1.SumComponentSqrs() <= v2.SumComponentSqrs();
}
Greaterthan (result = v1 > v2)
Greaterthan compares two vectors returning true only if the magnitude of the lefthandside vector (v1) is greater than the magnitude of the other (v2). Again we use the squared magnitude for efficiency.
public static bool operator>(Vector3 v1, Vector3 v2)
{
return v1.SumComponentSqrs() > v2.SumComponentSqrs();
}
Greaterthan or Equalto (result = v1 >= v2)
Greaterthan or equalto compares two vectors returning true only if the magnitude of the lefthandside vector (v1) is greater than the magnitude of the other (v2) or the two magnitudes are equal. Again we use the squared magnitude for efficiency.
public static bool operator>(Vector3 v1, Vector3 v2)
{
return v1.SumComponentSqrs() >= v2.SumComponentSqrs();
}
Equality (result = v1 == v2)
To check if two vectors are equal we simply check the component pairs. We AND the results so that any pair which is not equal will result in false.
public static bool operator==(Vector3 v1, Vector3 v2)
{
return
v1.X == v2.X &&
v1.Y == v2.Y &&
v1.Z == v2.Z;
}
If the operator == (equal) is overridden, C# forces us to override != (notequal). This is simply the inverse of equality.
public static bool operator!=(Vector3 v1, Vector3 v2)
{
return !(v1 == v2);
}
Equals
The Equals
method checks for equality between two vectors and implements the IEquitable
and IEquatable<Vector3>
interfaces provided by the .Net framework. In most cases the result is identical to the == operator. However, one of the special values of a double, the NaN (Not a number), works differently.
 NaN == NaN is false
 NaN.Equals(NaN) is true
This is consistent with the operator == and implementation of .Equals for a double. The reasons for this are described in this article.
public override bool Equals(object other)
{
if(other is Vector3)
{
Vector3 otherVector = (Vector3)other;
return otherVector.Equals(this);
}
else
{
return false;
}
}
public bool Equals(Vector3 other)
{
return
this.X.Equals(other.X) &&
this.Y.Equals(other.Y) &&
this.Z.Equals(other.Z);
}
As mentioned, the Equals
method can be overloaded to allow a tolerance value.
public bool Equals(object other, double tolerance)
{
if (other is Vector3)
{
return this.Equals((Vector3)other, tolerance);
}
return false;
}
public bool Equals(Vector3 other, double tolerance)
{
return
AlmostEqualsWithAbsTolerance(this.X, other.X, tolerance) &&
AlmostEqualsWithAbsTolerance(this.Y, other.Y, tolerance) &&
AlmostEqualsWithAbsTolerance(this.Z, other.Z, tolerance);
}
public static bool AlmostEqualsWithAbsTolerance(double a, double b, double maxAbsoluteError)
{
double diff = Math.Abs(a  b);
if (a.Equals(b))
{
return true;
}
return diff <= maxAbsoluteError;
}
GetHashCode
The GetHashCode
method is defined on the base class for all objects in C# to provide quick equality comparisons for hash based collections such as Dictionary
. Hash code comparisons should produce the same result as the Equals method so we must override GetHashCode
when we override the Equals
method. For more information see MSDN.
The hash codes of each of the component parts of the vector are bitwise combined with XOR. The prime number 397 is of sufficient size to cause the component hash code to overflow providing a better distribution of hash codes. unchecked
stops the compiler from checking for numeric overflow, which in this unusual situation is something we want. There are many valid ways to compute a hash code.
public override int GetHashCode()
{
unchecked
{
var hashCode = this.x.GetHashCode();
hashCode = (hashCode * 397) ^ this.y.GetHashCode();
hashCode = (hashCode * 397) ^ this.z.GetHashCode();
return hashCode;
}
}
CompareTo
The CompareTo
method implements a comparison of two vectors which returns:
 1 if the magnitude is less than the others magnitude
 0 if the magnitude equals the magnitude of the other
 1 if the magnitude is greater than the magnitude of the other
This allows the vector type to implement the IComparable
and IComparable<Vector3>
interfaces provided by the .Net framework.
public int CompareTo(object other)
{
if (other is Vector3)
{
return this.CompareTo((Vector3)other);
}
throw new ArgumentException(
NON_VECTOR_COMPARISON + "\n" +
ARGUMENT_TYPE + other.GetType().ToString(),
"other");
}
public int CompareTo(Vector3 other)
{
if (this < other)
{
return 1;
}
else if (this > other)
{
return 1;
}
return 0;
}
private const string NON_VECTOR_COMPARISON =
"Cannot compare a Vector3 to a nonVector3";
private const string ARGUMENT_TYPE =
"The argument provided is a type of ";
Again, CompareTo
can be overloaded to allow a tolerance value. Here the absolute tolerance calculation is handled by the Equals
method overload.
public int CompareTo(object other, double tolerance)
{
if (other is Vector3)
{
return this.CompareTo((Vector3)other, tolerance);
}
throw new ArgumentException(
NON_VECTOR_COMPARISON + "\n" +
ARGUMENT_TYPE + other.GetType().ToString(),
"other" );
}
public int CompareTo(Vector3 other, double tolerance)
{
var bothInfinite =
double.IsInfinity(this.SumComponentSqrs()) &&
double.IsInfinity(other.SumComponentSqrs());
if (this.Equals(other, tolerance)  bothInfinite)
{
return 0;
}
if (this < other)
{
return 1;
}
return 1;
}
Multiplication (dot, cross, and by scalar)
Multiplication of vectors is tricky. There are three distinct types of vector multiplication:
 Multiplication by a scalar (v3 = v1 * s2)
 Dot product (s3 = v1 . v2)
 Cross product (v3 = v1 * v2)
Only multiplication by scalar and division by scalar have been implemented as operator overloads. I have seen operators such as ~
overloaded for the dot product to distinguish it from cross product; I believe that this can lead to confusion and have chosen not to provide operators for dot and cross products leaving the user to call the appropriate method instead.
Multiplication by scalar is achieved by multiplying each of the component parts by the scalar value.
public static Vector3 operator*(Vector3 v1, double s2)
{
return
new Vector3
(
v1.X * s2,
v1.Y * s2,
v1.Z * s2
);
}
The order of operands in multiplication can be reversed; this is known as being commutable.
public static Vector3 operator*(double s1, Vector3 v2)
{
return v2 * s1;
}
The cross product of two vectors produces a normal to the plane created by the two vectors given.
The formula for this (where v1 = A and v2 = B) is
This equation always produces a vector as the result.
The sine of theta is used to account for the direction of the vector. Theta always takes the smallest angle between A and B (i.e. ).
The right hand side of the formula is arrived at by expanding and simplifying the left hand side using the rules:
Sin 0° = 0
Sin 90° = 1
In a matrix style notation this looks like:
You should be aware that this equation is noncommutable. This means that v1 crossproduct v2 is NOT the same as v2 crossproduct v1.
The C# code for all of this is:
public static Vector3 CrossProduct(Vector3 v1, Vector3 v2)
{
return
new Vector3
(
v1.Y * v2.Z  v1.Z * v2.Y,
v1.Z * v2.X  v1.X * v2.Z,
v1.X * v2.Y  v1.Y * v2.X
);
}
Where possible I have created static methods to extend the programmer's options when making use of the type. Methods which directly affect or are effected by the instance simply call the static methods. As such the instance counterpart of the static method is:
public Vector3 CrossProduct(Vector3 other)
{
return CrossProduct(this, other);
}
Note that this instance method does not affect the instance from which it is called but returns a new Vector3
object. I have chosen to implement cross product in this fashion for two reasons; one, to make it consistent with dot product which cannot produce a vector, and two, because cross product is usually used to generate a normal used somewhere else, the original Vector3
needing to be left intact.
[Side note] A quick template for manually calculating the cross product of two vectors is:
The dot product of two vectors is a scalar value defined by the formula;
The equation should always produce a scalar as the result.
Cosine theta is used to account for the direction of the vector. Theta always takes the smallest angle between A and B (i.e. ).
The right hand side of the formula is arrived at by expanding and simplifying the left hand side using the rules:
Cos 0° =1
Cos 90° = 0
The C# code for this is:
public static double DotProduct(Vector3 v1, Vector3 v2)
{
return
(
v1.X * v2.X +
v1.Y * v2.Y +
v1.Z * v2.Z
);
}
And its counterpart:
public double DotProduct(Vector3 other)
{
return DotProduct(this, other);
}
Division
Division of a vector by a scalar number (e.g. 2) is achieved by dividing each of the component parts by the divisor (s2).
public static Vector3 operator/(Vector3 v1, double s2)
{
return
(
new Vector3
(
v1.X / s2,
v1.Y / s2,
v1.Z / s2
)
);
}
Extended functionality
We now have all the basic functionality required of a Vector3
type. To make this type really useful I have provided additional functionality.
Normalisation and Unit Vector
A unit vector has a magnitude of 1. To test if a vector is a unit vector we simply check for 1 against the magnitude method already defined.
public static bool IsUnitVector(Vector3 v1)
{
return v1.Magnitude == 1;
}
public bool IsUnitVector()
{
return IsUnitVector(this);
}
As this is a comparison we also provide a tolerant overload.
public bool IsUnitVector(double tolerance)
{
return IsUnitVector(this, tolerance);
}
public static bool IsUnitVector(Vector3 v1, double tolerance)
{
return AlmostEqualsWithAbsTolerance(v1.Magnitude, 1, tolerance);
}
Normalization is the process of converting some vector to a unit vector. The formula for this is:
There are a number of special cases that need to be handled when implementing this formula:
 The vector to be normalised has no magnitude.
 The vector to be normalised is already a unit vector.
 The vector to be normalised has one or more components (x,y,z) of NaN.
 The vector has an infinte magnitude and components are all (+/) infinity or (+/) 0.
 The vector has an infinite magnitude with real number components.
Mathematically you cannot normalise a vector with a magnitude of 0, however, for convenience to the programmer, many vector implementations will return a zero vector (0,0,0). Similarly, for all of the special cases listed there varying results in the implementations I have found from other libraries.
The first implementation for normalisation that I provide throws exceptions for the special cases except where a mathematically correct value can be provided, for example (infinity, 0, 0) when normalised is (1,0,0).
public static Vector3 Normalize(Vector3 v1)
{
var magnitude = v1.Magnitude;
if (magnitude == 0)
{
throw new NormalizeVectorException(NORMALIZE_0);
}
if (double.IsNaN(magnitude))
{
throw new NormalizeVectorException(NORMALIZE_NaN);
}
if (double.IsInfinity(v1.Magnitude))
{
var x =
v1.X == 0 ? 0 :
v1.X == 0 ? 0 :
double.IsPositiveInfinity(v1.X) ? 1 :
double.IsNegativeInfinity(v1.X) ? 1 :
double.NaN;
var y =
v1.Y == 0 ? 0 :
v1.Y == 0 ? 0 :
double.IsPositiveInfinity(v1.Y) ? 1 :
double.IsNegativeInfinity(v1.Y) ? 1 :
double.NaN;
var z =
v1.Z == 0 ? 0 :
v1.Z == 0 ? 0 :
double.IsPositiveInfinity(v1.Z) ? 1 :
double.IsNegativeInfinity(v1.Z) ? 1 :
double.NaN;
var result = new Vector3(x, y, z);
if (result.IsNaN())
{
throw new NormalizeVectorException(NORMALIZE_Inf);
}
return result;
}
return NormalizeOrNaN(v1);
}
public Vector3 Normalize()
{
return Normalize(this);
}
private static Vector3 NormalizeOrNaN(Vector3 v1)
{
double inverse = 1 / v1.Magnitude;
return new Vector3(
v1.X * inverse,
v1.Y * inverse,
v1.Z * inverse);
}
private const string NORMALIZE_0 =
"Cannot normalize a vector when it's magnitude is zero";
private const string NORMALIZE_NaN =
"Cannot normalize a vector when it's magnitude is NaN";
I have also implemented an alternative method that will behave differently for exceptional conditions. NormalizeOrDefault
will return a vector of (0,0,0) if the magnitude is 0 or vector (NaN,NaN,NaN) if any of the components are NaN.
public static Vector3 NormalizeOrDefault(Vector3 v1)
{
if (v1.Magnitude == 0)
{
return Origin;
}
if (v1.IsNaN())
{
return NaN;
}
if (double.IsInfinity(v1.Magnitude))
{
var x =
v1.X == 0 ? 0 :
v1.X == 0 ? 0 :
double.IsPositiveInfinity(v1.X) ? 1 :
double.IsNegativeInfinity(v1.X) ? 1 :
double.NaN;
var y =
v1.Y == 0 ? 0 :
v1.Y == 0 ? 0 :
double.IsPositiveInfinity(v1.Y) ? 1 :
double.IsNegativeInfinity(v1.Y) ? 1 :
double.NaN;
var z =
v1.Z == 0 ? 0 :
v1.Z == 0 ? 0 :
double.IsPositiveInfinity(v1.Z) ? 1 :
double.IsNegativeInfinity(v1.Z) ? 1 :
double.NaN;
var result = new Vector3(x, y, z);
return result.IsNaN() ? NaN : result;
}
return NormalizeOrNaN(v1);
}
public Vector3 NormalizeOrDefault()
{
return NormalizeOrDefault(this);
}
The developer using this Vector3
code should choose the correct overload for their application. The difference is that Normalize
will require exception handlers but will tell the developer what the exceptional circumstance was and the NormalizeOrDefault
method will allow execution to continue but the calling code must be able to handle the unusual results.
Absolute
The absolute value of a vector is its magnitude. The Abs
method has been provided to help programmers who are not aware that the two functions are the same and provide a static interface to the magnitude operator.
public static Double Abs(Vector3 v1)
{
return v1.Magnitude;
}
public double Abs()
{
return this.Magnitude;
}
Angle
This method finds the angle between two vectors using normalization and dot product.
^ refers to a normalized (unit) vector.
 refers to the magnitude of a Vector.
Due the inherent inprecision of calculations on decimal numbers in a binary system, calculations that should produce an angle of 0 or 1 radian will often be slightly out. To illeviate this, the test for equality and Min have been added to "snap" results back into the correct range. Thanks to Dennis E. Cox in the comments for this solution.
public static double Angle(Vector3 v1, Vector3 v2)
{
if (v1 == v2)
{
return 0;
}
return
Math.Acos(
Math.Min(1.0f, NormalizeOrDefault(v1).DotProduct(NormalizeOrDefault(v2))));
}
public double Angle(Vector3 other)
{
return Angle(this, other);
}
Backface
This method interprets a vector as a face normal and determines whether the normal represents a back facing plane given a lineofsight vector. A back facing plane will be invisible in a rendered scene and as such can be except from many scene calculations.
If then if
If then if
public static bool IsBackFace(Vector3 normal, Vector3 lineOfSight)
{
return normal.DotProduct(lineOfSight) < 0;
}
public bool IsBackFace(Vector3 lineOfSight)
{
return IsBackFace(this, lineOfSight);
}
Distance
This method finds the distance between two positional vectors using Pythagoras theorem.
public static double Distance(Vector3 v1, Vector3 v2)
{
return
Math.Sqrt
(
(v1.X  v2.X) * (v1.X  v2.X) +
(v1.Y  v2.Y) * (v1.Y  v2.Y) +
(v1.Z  v2.Z) * (v1.Z  v2.Z)
);
}
public double Distance(Vector3 other)
{
return Distance(this, other);
}
Interpolation & Extrapolation
This method takes an interpolated value from between two vectors. This method takes three arguments, a starting point (vector v1), and end point (Vector v2), and a control which is a fraction between 1 and 0. The control determines which point between v1 and v2 is taken. A control of 0 will return v1 and a control of 1 will return v2.
n = n1(1t) + n2t
or:
n = n1 + t(n2n1)
or:
n = n1 + tn2 tn1
or:
where:
n = Current value
n_{1}_{ }= Initial value (v1)
n_{2}_{ }= Final value (v2)
t = Control parameter, where , and where, ,
Extrapolation, where the control value is greter than one or less than 0, is allowed but only if a flag is set. This allows vectors to be returned that sit on the immaginary line that passes through both v1 and v2 but does not have to be between the two.
public static Vector3 Interpolate(
Vector3 v1,
Vector3 v2,
double control,
bool allowExtrapolation)
{
if (!allowExtrapolation && (control > 1  control < 0))
{
throw new ArgumentOutOfRangeException(
"control",
control,
INTERPOLATION_RANGE + "\n" + ARGUMENT_VALUE + control);
}
return new Vector3(
v1.X * (1  control) + v2.X * control,
v1.Y * (1  control) + v2.Y * control,
v1.Z * (1  control) + v2.Z * control);
}
public static Vector3 Interpolate(Vector3 v1, Vector3 v2, double control)
{
return Interpolate(v1, v2, control, false);
}
public Vector3 Interpolate(Vector3 other, double control)
{
return Interpolate(this, other, control);
}
public Vector3 Interpolate(Vector3 other, double control, bool allowExtrapolation)
{
return Interpolate(this, other, control);
}
private const string INTERPOLATION_RANGE =
"Control parameter must be a value between 0 & 1";
Max and Min
These methods compare the magnitude of two vectors and return the vector with the largest or smallest magnitude respectively.
public static Vector3 Max(Vector3 v1, Vector3 v2)
{
return v1 >= v2 ? v1 : v2;
}
public Vector3 Max(Vector3 other)
{
return Max(this, other);
}
public static Vector3 Min(Vector3 v1, Vector3 v2)
{
return v1 <= v2 ? v1 : v2;
}
public Vector3 Min(Vector3 other)
{
return Min(this, other);
}
Mixed Product
The code for this method was provided by Michał Bryłka. The method calculates the scalar triple product of three vectors. This is the volume of a parallelepiped geometric shape. More information is available on Wikipedia. This method is noncommutable.
public static double MixedProduct(Vector3 v1, Vector3 v2, Vector3 v3)
{
return DotProduct(CrossProduct(v1, v2), v3);
}
public double MixedProduct(Vector3 other_v1, Vector3 other_v2)
{
return DotProduct(CrossProduct(this, other_v1), other_v2);
}
Perpendicular
This method checks if two vectors are perpendicular (i.e. if one vector is the normal of the other).
public static bool IsPerpendicular(Vector3 v1, Vector3 v2)
{
v1 = NormalizeSpecialCasesOrOrigional(v1);
v2 = NormalizeSpecialCasesOrOrigional(v2);
if (v1 == Zero  v2 == Zero)
{
return false;
}
return v1.DotProduct(v2).Equals(0);
}
public bool IsPerpendicular(Vector3 other)
{
return IsPerpendicular(this, other);
}
private static Vector3 NormalizeSpecialCasesOrOrigional(Vector3 v1)
{
if (double.IsInfinity(v1.Magnitude))
{
var x =
v1.X == 0 ? 0 :
v1.X == 0 ? 0 :
double.IsPositiveInfinity(v1.X) ? 1 :
double.IsNegativeInfinity(v1.X) ? 1 :
double.NaN;
var y =
v1.Y == 0 ? 0 :
v1.Y == 0 ? 0 :
double.IsPositiveInfinity(v1.Y) ? 1 :
double.IsNegativeInfinity(v1.Y) ? 1 :
double.NaN;
var z =
v1.Z == 0 ? 0 :
v1.Z == 0 ? 0 :
double.IsPositiveInfinity(v1.Z) ? 1 :
double.IsNegativeInfinity(v1.Z) ? 1 :
double.NaN;
return new Vector3(x, y, z);
}
return v1;
}
Some of the special case logic found in the Normalize
method has been extracted into a private class for this slightly different useage. This is simply for code reuse and seperation of concerns.
public static bool IsPerpendicular(Vector3 v1, Vector3 v2, double tolerance)
{
v1 = NormalizeSpecialCasesOrOrigional(v1);
v2 = NormalizeSpecialCasesOrOrigional(v2);
if (v1 == Zero  v2 == Zero)
{
return false;
}
return v1.DotProduct(v2).AlmostEqualsWithAbsTolerance(0, tolerance);
}
public bool IsPerpendicular(Vector3 other, double tolerance)
{
return IsPerpendicular(this, other, tolerance);
}
private static bool AlmostEqualsWithAbsTolerance(
this double a,
double b,
double maxAbsoluteError)
{
double diff = Math.Abs(a  b);
if (a.Equals(b))
{
return true;
}
return diff <= maxAbsoluteError;
}
Projection and Rejection
A vector can be projected onto another using the formula:
Projection is the transformation of a vector on one plane onto another. You can visualise this as shining a light from the pane of the original vector onto a card (the target plane).
^{Image from: Weisstein, Eric W. "Projection." From MathWorldA Wolfram Web Resource. http://mathworld.wolfram.com/Projection.html}
Shown with two vectors this looks like:
In the code this is:
public static Vector3 Projection(Vector3 v1, Vector3 v2)
{
return new Vector3(v2 * (v1.DotProduct(v2) / Math.Pow(v2.Magnitude, 2)));
}
public Vector3 Projection(Vector3 direction)
{
return Projection(this, direction);
}
Rejection is the vector representing the change of a vector’s projection to its original value.
The formula for this is simply:
Or
In the code this is:
public static Vector3 Rejection(Vector3 v1, Vector3 v2)
{
return v1  v1.Projection(v2);
}
public Vector3 Rejection(Vector3 direction)
{
return Rejection(this, direction);
}
Reflection
Reflect a vector about another to provide a mirror image of the original vector.
The formula for this is:
And in code:
public Vector3 Reflection(Vector3 reflector)
{
this = Vector3.Reflection(this, reflector);
return this;
}
public static Vector3 Reflection(Vector3 v1, Vector3 v2)
{
if (Math.Abs(Math.Abs(v1.Angle(v2))  Math.PI / 2) < Double.Epsilon)
{
return v1;
}
Vector3 retval = new Vector3(2 * v1.Projection(v2)  v1);
return retval.Scale(v1.Magnitude);
}
Rotation
Euler rotation around axis x,y,z is performed using the methods RotateX
, RotateY
and RotateZ
.
While these methods are unambiguous I prefer the more contextful pitch, yaw, and roll respectively.
Eric__ commented that he would expect a different configuration.
"... Roll, pitch and yaw refer back to the concept of an aircraft's motion.
It is standard notation that X is forward (out the nose), Y is out the right wing and Z is down (toward Earth for level flight).
Therefore it follows that roll is positive about +X, Pitch is positive about +Y (pitchup means climb), and Yaw is positive around +Z (positive yaw is when the aircraft nose moves to the right)."
To illustrate his point consider the following diagram:
This would appear to make perfect sense. It does! But only when considering the single aeroplane object. When we consider a virtual scene with multiple objects (for example a computer game or virtual reality environment), all objects must be relevant to the user perceiving them. The standard axis for a virtual scene have the user look down the Z axis.
So taking the aeroplane example, it is quite probable that we will be following the aircraft as it flies into the scene:
Hopefully, this explains why the axis are as described and the pitch, yaw, roll configuration is such.
Pitch (RotateX)
RotateX
or Pitch
rotates a vector around the X axis by a given number of radians (Euler rotation around X).
The hypotenuse (R) cancels out in the equation.
public static Vector3 RotateX(Vector3 v1, double rad)
{
double x = v1.X;
double y = (v1.Y * Math.Cos(rad))  (v1.Z * Math.Sin(rad));
double z = (v1.Y * Math.Sin(rad)) + (v1.Z * Math.Cos(rad));
return new Vector3(x, y, z);
}
public Vector3 RotateX(double rad)
{
return RotateX(this, rad);
}
public static Vector3 Pitch(Vector3 v1, double rad)
{
return RotateX(v1, rad);
}
public Vector3 Pitch(double rad)
{
return Pitch(this, rad);
}
Yaw (RotateY)
RotateY
or Yaw
rotates a vector around the Y axis by a given number of degrees (Euler rotation around Y).
The hypotenuse (R) cancels out in the equation.
public static Vector3 RotateY(Vector3 v1, double rad)
{
double x = (v1.Z * Math.Sin(rad)) + (v1.X * Math.Cos(rad));
double y = v1.Y;
double z = (v1.Z * Math.Cos(rad))  (v1.X * Math.Sin(rad));
return new Vector3(x, y, z);
}
public Vector3 RotateY(double rad)
{
return RotateY(this, rad);
}
public static Vector3 Yaw(Vector3 v1, double rad)
{
return RotateY(v1, rad);
}
public Vector3 Yaw(double rad)
{
return Yaw(this, rad);
}
Roll (RotateZ)
RotateZ
or Roll
rotates a vector around the Z axis by a given number of radians (Euler rotation around Z).
The hypotenuse (R) cancels out in the equation.
public static Vector3 RotateZ(Vector3 v1, double rad)
{
double x = (v1.X * Math.Cos(rad))  (v1.Y * Math.Sin(rad));
double y = (v1.X * Math.Sin(rad)) + (v1.Y * Math.Cos(rad));
double z = v1.Z;
return new Vector3(x, y, z);
}
public Vector3 RotateZ(double rad)
{
return RotateZ(this, rad);
}
public static Vector3 Roll(Vector3 v1, double rad)
{
return RotateZ(v1, rad);
}
public Vector3 Roll(double rad)
{
return Roll(this, rad);
}
Arbitary Rotation
Methods to rotate the vector arround a specified point have been implemented. This can also be thought of as offseting the axis before rotation.
public static Vector3 RotateX(Vector3 v1, double yOff, double zOff, double rad)
{
double x = v1.X;
double y =
(v1.Y * Math.Cos(rad))  (v1.Z * Math.Sin(rad)) +
(yOff * (1  Math.Cos(rad)) + zOff * Math.Sin(rad));
double z =
(v1.Y * Math.Sin(rad)) + (v1.Z * Math.Cos(rad)) +
(zOff * (1  Math.Cos(rad))  yOff * Math.Sin(rad));
return new Vector3(x, y, z);
}
public Vector3 RotateX(double yOff, double zOff, double rad)
{
return RotateX(this, yOff, zOff, rad);
}
public static Vector3 RotateY(Vector3 v1, double xOff, double zOff, double rad)
{
double x =
(v1.Z * Math.Sin(rad)) + (v1.X * Math.Cos(rad)) +
(xOff * (1  Math.Cos(rad))  zOff * Math.Sin(rad));
double y = v1.Y;
double z =
(v1.Z * Math.Cos(rad))  (v1.X * Math.Sin(rad)) +
(zOff * (1  Math.Cos(rad)) + xOff * Math.Sin(rad));
return new Vector3(x, y, z);
}
public Vector3 RotateY(double xOff, double zOff, double rad)
{
return RotateY(this, xOff, zOff, rad);
}
public static Vector3 RotateZ(Vector3 v1, double xOff, double yOff, double rad)
{
double x =
(v1.X * Math.Cos(rad))  (v1.Y * Math.Sin(rad)) +
(xOff * (1  Math.Cos(rad)) + yOff * Math.Sin(rad));
double y =
(v1.X * Math.Sin(rad)) + (v1.Y * Math.Cos(rad)) +
(yOff * (1  Math.Cos(rad))  xOff * Math.Sin(rad));
double z = v1.Z;
return new Vector3(x, y, z);
}
public Vector3 RotateZ(double xOff, double yOff, double rad)
{
return RotateZ(this, xOff, yOff, rad);
}
Rounding
These methods round the components of a vector to:
 The nearest integral value:
public static Vector3 Round(Vector3 v1)
{
return new Vector3(Math.Round(v1.X), Math.Round(v1.Y), Math.Round(v1.Z));
}
public static Vector3 Round(Vector3 v1, MidpointRounding mode)
{
return new Vector3(
Math.Round(v1.X, mode),
Math.Round(v1.Y, mode),
Math.Round(v1.Z, mode));
}
public Vector3 Round()
{
return new Vector3(Math.Round(this.X), Math.Round(this.Y), Math.Round(this.Z));
}
public Vector3 Round(MidpointRounding mode)
{
return new Vector3(
Math.Round(this.X, mode),
Math.Round(this.Y, mode),
Math.Round(this.Z, mode));
}
 A specified number of digits:
public static Vector3 Round(Vector3 v1, int digits)
{
return new Vector3(
Math.Round(v1.X, digits),
Math.Round(v1.Y, digits),
Math.Round(v1.Z, digits));
}
public static Vector3 Round(Vector3 v1, int digits, MidpointRounding mode)
{
return new Vector3(
Math.Round(v1.X, digits, mode),
Math.Round(v1.Y, digits, mode),
Math.Round(v1.Z, digits, mode));
}
public Vector3 Round(int digits)
{
return new Vector3(
Math.Round(this.X, digits),
Math.Round(this.Y, digits),
Math.Round(this.Z, digits));
}
public Vector3 Round(int digits, MidpointRounding mode)
{
return new Vector3(
Math.Round(this.X, digits, mode),
Math.Round(this.Y, digits, mode),
Math.Round(this.Z, digits, mode));
}
Scale
This method changes the magnitude of a vector to a specified value without changing the direction.
public static Vector3 Scale(Vector3 vector, double magnitude)
{
if (magnitude < 0)
{
throw new ArgumentOutOfRangeException("magnitude", magnitude, NEGATIVE_MAGNITUDE);
}
if (vector == new Vector3(0, 0, 0))
{
throw new ArgumentException(ORIGIN_VECTOR_MAGNITUDE, "vector");
}
return vector * (magnitude / vector.Magnitude);
}
public Vector3 Scale(double magnitude)
{
return Vector3.Scale(this, magnitude);
}
private const string NEGATIVE_MAGNITUDE =
"The magnitude of a Vector3 must be a positive value, (i.e. greater than 0)";
private const string ORIGIN_VECTOR_MAGNITUDE =
"Cannot change the magnitude of Vector3(0,0,0)";
Component Functions
I have provided a number of functions which target the vectors components. These are not mathematically valid for the vector as a whole. For example, there is no concept of raising a vector to a power (that I know of) however the PowComponents
method can be used to raise each of x,y,z to a given power.
Sum components
This method simply adds together the vector components (x, y, z).
public static double SumComponents(Vector3 v1)
{
return (v1.X + v1.Y + v1.Z);
}
public double SumComponents()
{
return SumComponents(this);
}
To Power
This method multiplies the vectors components to a given power.
public static Vector3 PowComponents(Vector3 v1, double power)
{
return
new Vector
(
Math.Pow(v1.X, power),
Math.Pow(v1.Y, power),
Math.Pow(v1.Z, power)
);
}
public void PowComponents(double power)
{
this = PowComponents(this, power);
}
Square root
This method applies the square root function to each of the vectors components.
public static Vector3 SqrtComponents(Vector3 v1)
{
return
(
new Vector3
(
Math.Sqrt(v1.X),
Math.Sqrt(v1.Y),
Math.Sqrt(v1.Z)
)
);
}
public void SqrtComponents()
{
this = SqrtComponents(this);
}
Square
This method squares to each of the vectors components.
public static Vector3 SqrComponents(Vector3 v1)
{
return
(
new Vector3
(
v1.X * v1.X,
v1.Y * v1.Y,
v1.Z * v1.Z
)
);
}
public void SqrComponents()
{
this = SqrtComponents(this);
}
Sum of squares
This method finds the sum of each of the vectors components squared.
public static double SumComponentSqrs(Vector3 v1)
{
Vector3 v2 = SqrComponents(v1);
return v2.SumComponents();
}
public double SumComponentSqrs()
{
return SumComponentSqrs(this);
}
Not A Number
If any of the components (x,y,z) are NaN the whole vector should be considered "Not A Number". This method returns true if any of the components (x,y,z) are NaN.
public static bool IsNaN(Vector3 v1)
{
return double.IsNaN(v1.X)  double.IsNaN(v1.Y)  double.IsNaN(v1.Z);
}
public bool IsNaN()
{
return IsNaN(this);
}
Usability functions
We have seen implementations for the .Net interfaces IComparable
, IComparable<Vector3>
, and IEquatable<Vector3>
. For completeness IFormattable
is also implemented. The method defined by the interface, ToString
, returns a textual description of the type.
VerbString
has also been provided to provide a verbose textual description. ToString
can accept a numeric format string optionally proceeded by a character x, y or z which indicates the relevant vector component to describe.
public string ToVerbString()
{
string output = null;
if (IsUnitVector())
{
output += UNIT_VECTOR;
}
else
{
output += POSITIONAL_VECTOR;
}
output += string.Format("( x={0}, y={1}, z={2})", X, Y, Z);
output += MAGNITUDE + Magnitude;
return output;
}
private const string UNIT_VECTOR =
"Unit vector composing of ";
private const string POSITIONAL_VECTOR =
"Positional vector composing of ";
private const string MAGNITUDE =
" of magnitude ";
public string ToString(string format, IFormatProvider formatProvider)
{
if (format == null  format == "")
return String.Format("({0}, {1}, {2})", X, Y, Z);
char firstChar = format[0];
string remainder = null;
if (format.Length > 1)
remainder = format.Substring(1);
switch (firstChar)
{
case 'x':
return X.ToString(remainder, formatProvider);
case 'y':
return Y.ToString(remainder, formatProvider);
case 'z':
return Z.ToString(remainder, formatProvider);
default:
return
String.Format
(
"({0}, {1}, {2})",
X.ToString(format, formatProvider),
Y.ToString(format, formatProvider),
Z.ToString(format, formatProvider)
);
}
}
public override string ToString()
{
return ToString(null, null);
}
Standard Cartesian vectors and constants
Finally four standard vector constants are defined:
public static readonly Vector3 Origin = new Vector3(0,0,0);
public static readonly Vector3 XAxis = new Vector3(1,0,0);
public static readonly Vector3 YAxis = new Vector3(0,1,0);
public static readonly Vector3 ZAxis = new Vector3(0,0,1);
And miscellaneous readonly values:
public static readonly Vector3 MinValue =
new Vector3(Double.MinValue, Double.MinValue, Double.MinValue);
public static readonly Vector3 MaxValue =
new Vector3(Double.MaxValue, Double.MaxValue, Double.MaxValue);
public static readonly Vector3 Epsilon =
new Vector3(Double.Epsilon, Double.Epsilon, Double.Epsilon);
public static readonly Vector3 Zero =
Origin;
public static readonly Vector3 NaN =
new Vector3(double.NaN, double.NaN, double.NaN);
Serialization
Vector3
implements the [Serializable]
attribute and can therefore be written to file. I suggest the following:
static void Main(string[] args)
{
Vector3 vect = new Vector3(1, 2, 3);
XmlSerializer x = new XmlSerializer(vect.GetType());
x.Serialize
(
new System.IO.FileStream("test.xml", System.IO.FileMode.Create),
vect
);
}
Which produces an XML file containing:
="1.0"
<Vector
xmlns:xsi="http://www.w3.org/2001/XMLSchemainstance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<X>1</X>
<Y>2</Y>
<Z>3</Z>
<Magnitude>3.7416573867739413</Magnitude>
</Vector>
Summary
We now have a Vector3
type with the following public functionality:
 Constructors
Vector3(double x, double y, double z) Vector3(double[] xyz) Vector3(Vector v1)
Properties
Operators
this[] Indexer +  == != * / < > <= >=
Static methods
CrossProduct DotProduct MixedProduct Normalize IsUnitVector Interpolate Distance Abs Angle Max Min Yaw Pitch Roll IsBackFace IsPerpendicular SumComponents SumComponentSqrs SqrComponents SqrtComponents PowComponents
Methods
Abs Angle CrossProduct Distance DotProduct Interpolate IsBackFace IsNaN IsPerpendicular IsUnitVector Max Min MixedProduct Normalize Pitch PowComponents Projection Reflection Rejection Roll RotateX RotateY RotateZ Round Scale SqrComponents SqrtComponents SumComponentSqrs ToVerbString Yaw
Methods Implementing Interfaces
CompareTo Equals ToString GetHashCode
Readonly and constant values
Epsilon MaxValue MinValue NaN Origin xAxis yAxis zAxis Zero

A quick comparison of some of the common features in a selection of libraries that support vectors in .Net. This article’s code execution speed appears to be somewhere in the middle of the selection.
Some of the faster libraries are using floats not doubles and it should be noted that the cross product result for Math.Net is likely a misunderstanding of the library and should probably be ignored.
Points of Interest
There were a number of resources I used during the development of this article and source code provided, I would like to acknowledge the following:
 CSOpenGL Project  Lucas Viñas Livschitz
 Exocortex Project  Ben Houston
 Essential Mathematics for Computer Graphics  John Vince (ISBN 1852333804)
 Wolfram Mathworld Website
History
(v1.00v1.20)
Magnitude
methods are now encapsulated in a property  Incorrect serialization attributes have been removed
Equality
and IsUnitVector
methods allow a tolerance Abs
method now returns magnitude  Generic
IEquatable
and IComparable
interfaces have been implemented IFormattable
interface has been implemented  Mixed Product function implemented
 Added and renamed additional component based functions (e.g.
SumComponentSquares
) Vector
renamed to Vector3
(v1.20v1.30)
 Square components method was pointing to the square root static method
 Added comments about meaning of comparison operations on two vectors
 Changed references to degrees to radians
 Changed the implementation of
Angle
to help avoid NaN results  The
Vector3
class is now immutable, property setters have been removed and mutable methods return a new Vector3
 Updated comments to read better under intellisense.
 Added
Projection
, Rejection
and Reflection
operations  Split up operations into regions
 Added scale operations which used to be accessable through the magnitude mutable property
 Changed the
Equals(object)
method to use Equals(Vector3)
 Added component rounding operations
 Added rotate arround x, y or z (with or without axis offsets)
 Added
Equals
overloads with an absolute tolerace parameters  Added
IsUnitVector
overloads with absolute tolerance parameters  Added
IsPerpendicular
overloads with absolute toleerance parameters  Added
CompareTo
overloads with absolut tolerance parameters  Fixed an infinity issue in the
CompareTo
method  Unit testing proved that
NaN == NaN
is not the same as Nan.Equals(NaN)
 Altered .Equals method to be consistent with the .Net framework  Added
IsNaN
methods  Added
NormalizeOrDefault
method  Added special cases where we can normalize vectors with infinite components.
IsPerpendicular
now uses NormalizeOrDefault
to account for special cases of infinty.
Director at RADD Solutions Limited, a software development and consultation company in the UK.