From 40398d67cd3e4f74b08649eda428dc411d801fd5 Mon Sep 17 00:00:00 2001
From: Christophe Riccio <christophe.riccio@unity3d.com>
Date: Sat, 8 Apr 2017 19:37:20 +0200
Subject: [PATCH] Added vec2 cross #621

---
 glm/gtx/exterior_product.hpp      | 40 +++++++++++++++++++++++++++++++
 glm/gtx/exterior_product.inl      | 27 +++++++++++++++++++++
 readme.md                         |  1 +
 test/gtx/CMakeLists.txt           |  1 +
 test/gtx/gtx_exterior_product.cpp | 14 +++++++++++
 5 files changed, 83 insertions(+)
 create mode 100644 glm/gtx/exterior_product.hpp
 create mode 100644 glm/gtx/exterior_product.inl
 create mode 100644 test/gtx/gtx_exterior_product.cpp

diff --git a/glm/gtx/exterior_product.hpp b/glm/gtx/exterior_product.hpp
new file mode 100644
index 00000000..b7917494
--- /dev/null
+++ b/glm/gtx/exterior_product.hpp
@@ -0,0 +1,40 @@
+/// @ref gtx_exterior_product
+/// @file glm/gtx/exterior_product.hpp
+///
+/// @see core (dependence)
+/// @see gtx_exterior_product (dependence)
+///
+/// @defgroup gtx_exterior_product GLM_GTX_exterior_product
+/// @ingroup gtx
+/// 
+/// @brief Allow to perform bit operations on integer values
+/// 
+/// <glm/gtc/bitfield.hpp> need to be included to use these functionalities.
+
+#pragma once
+
+// Dependencies
+#include "../detail/setup.hpp"
+#include "../detail/precision.hpp"
+
+#if GLM_MESSAGES == GLM_MESSAGES_ENABLED && !defined(GLM_EXT_INCLUDED)
+#	pragma message("GLM: GLM_GTX_exterior_product extension included")
+#endif
+
+namespace glm
+{
+	/// @addtogroup gtx_exterior_product
+	/// @{
+
+	/// Returns the cross product of x and y.
+	///
+	/// @tparam valType Floating-point scalar types.
+	/// 
+	/// @see <a href="https://en.wikipedia.org/wiki/Exterior_algebra#Cross_and_triple_products">Exterior product</a>
+	template<typename T, precision P>
+	GLM_FUNC_DECL T cross(vec<2, T, P> const& v, vec<2, T, P> const& u);
+
+	/// @}
+} //namespace glm
+
+#include "exterior_product.inl"
diff --git a/glm/gtx/exterior_product.inl b/glm/gtx/exterior_product.inl
new file mode 100644
index 00000000..fc9376fc
--- /dev/null
+++ b/glm/gtx/exterior_product.inl
@@ -0,0 +1,27 @@
+/// @ref core
+/// @file glm/detail/func_geometric.inl
+
+#include <limits>
+
+namespace glm {
+namespace detail
+{
+	template<typename T, precision P, bool Aligned>
+	struct compute_cross_vec2
+	{
+		GLM_FUNC_QUALIFIER static T call(vec<2, T, P> const& v, vec<2, T, P> const& u)
+		{
+			GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'cross' accepts only floating-point inputs");
+
+			return v.x * u.y - u.x * v.y;
+		}
+	};
+}//namespace detail
+
+	template<typename T, precision P>
+	GLM_FUNC_QUALIFIER T cross(vec<2, T, P> const & x, vec<2, T, P> const & y)
+	{
+		return detail::compute_cross_vec2<T, P, detail::is_aligned<P>::value>::call(x, y);
+	}
+}//namespace glm
+
diff --git a/readme.md b/readme.md
index 53027a4e..109ad9fc 100644
--- a/readme.md
+++ b/readme.md
@@ -56,6 +56,7 @@ glm::mat4 camera(float Translate, glm::vec2 const & Rotate)
 - Added RGBM encoding in GTC_packing #420
 - Added GTX_color_encoding extension
 - Added GTX_vec_swizzle, faster compile time swizzling then swizzle operator #558
+- Added GTX_exterior_product with a vec2 cross implementation #621
 - Added [GLM_ENABLE_EXPERIMENTAL](manual.md#section7_4) to enable experimental features.
 
 #### Improvements:
diff --git a/test/gtx/CMakeLists.txt b/test/gtx/CMakeLists.txt
index a2731f80..6fe2fc27 100644
--- a/test/gtx/CMakeLists.txt
+++ b/test/gtx/CMakeLists.txt
@@ -9,6 +9,7 @@ glmCreateTestGTC(gtx_component_wise)
 glmCreateTestGTC(gtx_euler_angle)
 glmCreateTestGTC(gtx_extend)
 glmCreateTestGTC(gtx_extended_min_max)
+glmCreateTestGTC(gtx_exterior_product)
 glmCreateTestGTC(gtx_fast_exponential)
 glmCreateTestGTC(gtx_fast_square_root)
 glmCreateTestGTC(gtx_fast_trigonometry)
diff --git a/test/gtx/gtx_exterior_product.cpp b/test/gtx/gtx_exterior_product.cpp
new file mode 100644
index 00000000..a02c9830
--- /dev/null
+++ b/test/gtx/gtx_exterior_product.cpp
@@ -0,0 +1,14 @@
+#include <glm/gtx/exterior_product.hpp>
+#include <glm/gtc/epsilon.hpp>
+#include <glm/vec2.hpp>
+
+int main()
+{
+	int Error = 0;
+
+	float const f = glm::cross(glm::vec2(1.0f, 1.0f), glm::vec2(1.0f, 1.0f));
+	Error += glm::epsilonEqual(f, 0.0f, 0.001f) ? 0 : 1;
+
+	return Error;
+}
+