Graphics/AbstractViewer: Add ProjectDepth method

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)

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;

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());