Ticket #37: Added pickMatrix function

glm/gtc/matrix_transform.hpp

@@ -133,6 +133,14 @@ namespace glm
 			detail::tmat4x4<T> const & proj, 
 			detail::tvec4<U> const & viewport);
 
+		//! Define a picking region
+		//! From GLM_GTC_matrix_transform extension.
+		template <typename T, typename U> 
+		detail::tmat4x4<T> pickMatrix(
+			detail::tvec2<T> const & center, 
+			detail::tvec2<T> const & delta, 
+			detail::tvec4<U> const & viewport);
+
 		//! Build a look at view matrix.
 		//! From GLM_GTC_matrix_transform extension.
 		template <typename T> 

glm/gtc/matrix_transform.inl

@@ -324,6 +324,25 @@ namespace matrix_transform
 		return detail::tvec3<T>(obj);
 	}
 
+	template <typename T, typename U> 
+	detail::tmat4x4<T> pickMatrix
+	(
+		detail::tvec2<T> const & center, 
+		detail::tvec2<T> const & delta, 
+		detail::tvec4<U> const & viewport
+	)
+	{
+		assert(delta.x > 0.0f && delta.y > 0.0f)
+		detail::tmat4x4<T> Result(1.0f);
+
+		if(!(delta.x > 0.0f && delta.y > 0.0f)) 
+			return Result; // Error
+
+		// Translate and scale the picked region to the entire window
+		Result = translate(Result, (T(viewport[2]) - T(2) * (x - T(viewport[0]))) / delta.x, (T(viewport[3]) - T(2) * (y - T(viewport[1]))) / delta.y, T(0));
+		return scale(Result, T(viewport[2]) / delta.x, T(viewport[3]) / delta.y, T(1));
+	}
+
     template <typename T> 
     inline detail::tmat4x4<T> lookAt(
 		const detail::tvec3<T>& eye,