From db0e3267dad0d3b144b6e16e93110a964bfee7ff Mon Sep 17 00:00:00 2001
From: Lynix <lynix680@gmail.com>
Date: Tue, 29 May 2018 23:55:51 +0200
Subject: [PATCH] Graphics/AbstractViewer: Add ProjectDepth method

---
 ChangeLog.md                               | 1 +
 include/Nazara/Graphics/AbstractViewer.hpp | 2 ++
 src/Nazara/Graphics/AbstractViewer.cpp     | 9 +++++++++
 3 files changed, 12 insertions(+)

diff --git a/ChangeLog.md b/ChangeLog.md
index 98b92b55b..46704fd5d 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -105,6 +105,7 @@ Nazara Engine:
 - Added LuaState::Traceback method
 - Added ModelLibrary, ModelManager and ModelSaver
 - Added AbstractViewer::Project and AbstractViewer::Unproject methods
+- Added AbstractViewer::ProjectDepth method
 
 Nazara Development Kit:
 - Added ImageWidget (#139)
diff --git a/include/Nazara/Graphics/AbstractViewer.hpp b/include/Nazara/Graphics/AbstractViewer.hpp
index c682deeb2..36547b1ec 100644
--- a/include/Nazara/Graphics/AbstractViewer.hpp
+++ b/include/Nazara/Graphics/AbstractViewer.hpp
@@ -41,6 +41,8 @@ namespace Nz
 			virtual float GetZNear() const = 0;
 
 			Nz::Vector3f Project(const Nz::Vector3f& worldPosition) const;
+			float ProjectDepth(float depth);
+
 			Nz::Vector3f Unproject(const Nz::Vector3f& screenPos) const;
 
 			AbstractViewer& operator=(const AbstractViewer&) = default;
diff --git a/src/Nazara/Graphics/AbstractViewer.cpp b/src/Nazara/Graphics/AbstractViewer.cpp
index 2e5eb6b47..e9d91c92c 100644
--- a/src/Nazara/Graphics/AbstractViewer.cpp
+++ b/src/Nazara/Graphics/AbstractViewer.cpp
@@ -34,6 +34,15 @@ namespace Nz
 		return screenPosition;
 	}
 
+	float AbstractViewer::ProjectDepth(float depth)
+	{
+		const Matrix4f& projectionMatrix = GetProjectionMatrix();
+		float a = projectionMatrix(2, 2);
+		float b = projectionMatrix(2, 3);
+
+		return (0.5f * (-a * depth + b) / depth + 0.5f);
+	}
+
 	Vector3f AbstractViewer::Unproject(const Nz::Vector3f& screenPos) const
 	{
 		Rectf viewport = Rectf(GetViewport());