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Clean up the Swizzle Operators section

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Jesse Talavera-Greenberg 2015-11-27 17:31:52 -05:00
parent a6eda35cc6
commit e789f620dc
1 changed files with 8 additions and 11 deletions
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doc/doc.tex
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@ -212,11 +212,11 @@ vec3 D = B.rsz; // Invalid, won't compile
GLM optionally supports some of this functionality, through the methods described in the following sections. Swizzle operators can be enabled by defining \verb|GLM_SWIZZLE| before including any GLM header files, or as part of your project's build process.
\emph{Note that swizzle operators will massively increase the size of your binaries and the time it takes to compile them!}
\emph{Note that enabling swizzle operators will massively increase the size of your binaries and the time it takes to compile them!}
\subsection{Default C++98 Implementation}
When compiling as C++98, R-value swizzle operators are simulated through member functions of each vector type.
When compiling GLM as C++98, R-value swizzle operators are simulated through member functions of each vector type.
\begin{cppcode}
#define GLM_SWIZZLE // Or define when building (e.g. -DGLM_SWIZZLE)
@ -245,8 +245,8 @@ void foo()
{
glm::vec3 A(1.0f, 0.5f, 0.0f);
// No compiler error but A is not affected
// This code is modifying the components of an anonymous copy.
// No compiler error, but A is not modified.
// An anonymous copy is being modified (and then discarded).
A.bgr() = glm::vec3(2.0f, 1.5f, 1.0f); // A is not modified!
}
\end{cppcode}
@ -254,14 +254,13 @@ void foo()
\subsection{Anonymous Union Member Implementation}
Visual C++ supports, as a \emph{non-standard language extension}, anonymous \verb|struct|s in \verb|union|s. This enables a very powerful implementation of swizzle operators on Windows, which both allows L-value swizzle operators and reduces the need for parentheses. This implementation of the swizzle operators is only enabled when the language extension is enabled and \verb|GLM_SWIZZLE| is defined.
Visual C++ supports, as a \emph{non-standard language extension}, anonymous \verb|struct|s in \verb|union|s. This enables a very powerful implementation of swizzle operators on Windows, which both allows L-value swizzle operators and makes the syntax for it closer to GLSL's. This implementation of the swizzle operators is only enabled when the language extension is enabled and \verb|GLM_SWIZZLE| is defined.
\begin{cppcode}
#define GLM_SWIZZLE
#include <glm/glm.hpp>
// Only guaranteed to work with Visual C++!
//
// Some compilers that support Microsoft extensions may compile this.
void foo()
{
@ -278,7 +277,7 @@ void foo()
}
\end{cppcode}
This implementation returns implementation-specific objects that \emph{implicitly convert} to their respective vector types. Unfortunately, these extra types can't be interpreted by GLM functions, which means the programmer must convert a swizzle-made \say{vector} to a conventional vector type or call a swizzle object's \verb|operator()| to pass it to another C++ function.
This versions returns implementation-specific objects that \emph{implicitly convert} to their respective vector types. Unfortunately, these extra types can't be directly used by GLM functions; the programmer must instead convert a swizzle-made \say{vector} to a conventional vector type or call the swizzle object's \verb|operator()|.
\begin{cppcode}
#define GLM_SWIZZLE
@ -293,12 +292,10 @@ void foo()
// Generates compiler errors. Color.rgba is not a vector type.
vec4 ClampedA = glm::clamp(Color.rgba, 0.f, 1.f); // ERROR
// We need to cast the swizzled vector into glm::vec4
// Either use a constructor...
// Explicit conversion through a constructor
vec4 ClampedB = glm::clamp(vec4(Color.rgba), 0.f, 1.f); // OK
// ...or operator()
// Explicit conversion through operator()
vec4 ClampedC = glm::clamp(Color.rgba(), 0.f, 1.f); // OK
}
\end{cppcode}