Vec4¶
The Vec4
class template represents a 4D vector, with predefined
typedefs for vectors of type short
, int
, int64_t
,
float
, and double
.
Note that the integer specializations of Vec4
lack the
length()
and normalize()
methods that are present in the
float
and double
versions, because the results don’t fit into
integer quantities.
There are also various utility functions that operate on vectors
defined in ImathVecAlgo.h
and described in Vector Functions.
Individual components of a vector V
may be referenced as either V[i]
or V.x
, V.y
, V.z
, V.w
. Obviously, the []
notation is more
suited to looping over components, or in cases where a variable determines
which coordinate is needed. However, when the coordinate is known, it can be
more efficient to directly address the components, such as V.y
rather than
V[1]
. While both appear to do the same thing (and indeed do generate the
same machine operations for ordinary scalar code), when used inside loops that
you hope to parallelize (either through compiler auto-vectorization or
explicit hints such as #pragma omp simd
), the function call and
pointer casting of operator[]
can confuse the compiler just enough to
prevent vectorization of the loop.
Example:
#include <Imath/ImathVec.h>
#include <cassert>
void
vec4_example()
{
Imath::V4f a (1.0f, 2.0f, 3.0f, 4.0f);
Imath::V4f b; // b is uninitialized
b.x = a[0];
b.y = a[1];
b.z = a[2];
b.w = a[3];
assert (a == b);
assert (a.length() == sqrt (a ^ a));
a.normalize();
assert (Imath::equalWithAbsError (a.length(), 1.0f, 1e-6f));
}
-
template<class
T
>
classVec4
¶ 4-element vector
Constructors and Assignment
-
Vec4
()¶ Uninitialized by default.
-
constexpr
Vec4
(T a)¶ Initialize to a scalar
(a,a,a,a)
-
constexpr
Vec4
(T a, T b, T c, T d)¶ Initialize to given elements
(a,b,c,d)
-
constexpr const Vec4<T> &
operator=
(const Vec4 &v)¶ Assignment.
-
~Vec4
()¶ Destructor.
Arithmetic and Comparison
-
constexpr bool
equalWithAbsError
(const Vec4<T> &v, T e) const¶ Compare two matrices and test if they are “approximately equal”:
- Return
- True if the coefficients of this and
m
are the same with an absolute error of no more than e, i.e., for all i, j:abs (this[i][j] - m[i][j]) <= e
-
constexpr bool
equalWithRelError
(const Vec4<T> &v, T e) const¶ Compare two matrices and test if they are “approximately equal”:
- Return
- True if the coefficients of this and m are the same with a relative error of no more than e, i.e., for all i, j:
abs (this[i] - v[i][j]) <= e * abs (this[i][j])
-
constexpr T
dot
(const Vec4 &v) const¶ Dot product.
-
constexpr T
operator^
(const Vec4 &v) const¶ Dot product.
-
constexpr const Vec4<T> &
operator+=
(const Vec4 &v)¶ Component-wise addition.
-
constexpr Vec4<T>
operator+
(const Vec4 &v) const¶ Component-wise addition.
-
constexpr const Vec4<T> &
operator-=
(const Vec4 &v)¶ Component-wise subtraction.
-
constexpr Vec4<T>
operator-
(const Vec4 &v) const¶ Component-wise subtraction.
-
constexpr Vec4<T>
operator-
() const¶ Component-wise multiplication by -1.
-
constexpr const Vec4<T> &
negate
()¶ Component-wise multiplication by -1.
-
constexpr const Vec4<T> &
operator*=
(const Vec4 &v)¶ Component-wise multiplication.
-
constexpr const Vec4<T> &
operator*=
(T a)¶ Component-wise multiplication.
-
constexpr Vec4<T>
operator*
(const Vec4 &v) const¶ Component-wise multiplication.
-
constexpr Vec4<T>
operator*
(T a) const¶ Component-wise multiplication.
-
constexpr const Vec4<T> &
operator/=
(const Vec4 &v)¶ Component-wise division.
-
constexpr const Vec4<T> &
operator/=
(T a)¶ Component-wise division.
-
constexpr Vec4<T>
operator/
(const Vec4 &v) const¶ Component-wise division.
-
constexpr Vec4<T>
operator/
(T a) const¶ Component-wise division.
Query and Manipulation
-
T
length
() const¶ Return the Euclidean norm.
-
constexpr T
length2
() const¶ Return the square of the Euclidean norm, i.e.
the dot product with itself.
-
const Vec4<T> &
normalizeNonNull
()¶ Normalize without any checks for length()==0.
Slightly faster than the other normalization routines, but if v.length() is 0.0, the result is undefined.
-
Vec4<T>
normalized
() const¶ Return a normalized vector. Does not modify *this.
Numeric Limits
-
static constexpr T
baseTypeLowest
()¶ Largest possible negative value.
-
static constexpr T
baseTypeMax
()¶ Largest possible positive value.
-
static constexpr T
baseTypeSmallest
()¶ Smallest possible positive value.
-
static constexpr T
baseTypeEpsilon
()¶ Smallest possible e for which 1+e != 1.
Public Types
-
typedef T
BaseType
¶ The base type: In templates that accept a parameter
V
, you can refer toT
asV::BaseType
Public Functions
-
constexpr T &
operator[]
(int i)¶ Element access by index.
-
constexpr const T &
operator[]
(int i) const¶ Element access by index.
Public Static Functions
-
static constexpr unsigned int
dimensions
()¶ Return the number of dimensions, i.e. 4.
-
Warning
doxygenfunction: Unable to resolve multiple matches for function “operator<<” with arguments (std::ostream& s, const Vec4<T>& v) in doxygen xml output for project “Imath” from directory: /build/ilmbase-5Yemou/ilmbase-3.1.11/obj-x86_64-linux-gnu/website/doxygen/xml. Potential matches:
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