From 88b6ff63b7a090ee8b33f7f0fd4da7de799bb030 Mon Sep 17 00:00:00 2001
From: SirLynix <lynix680@gmail.com>
Date: Tue, 14 Mar 2023 18:07:03 +0100
Subject: [PATCH] Graphics/AbstractViewer: Add Project & Unproject methods

---
 include/Nazara/Graphics/AbstractViewer.hpp |  4 +++
 src/Nazara/Graphics/AbstractViewer.cpp     | 39 +++++++++++++++++++++-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/include/Nazara/Graphics/AbstractViewer.hpp b/include/Nazara/Graphics/AbstractViewer.hpp
index c03431c37..57dbfa4ef 100644
--- a/include/Nazara/Graphics/AbstractViewer.hpp
+++ b/include/Nazara/Graphics/AbstractViewer.hpp
@@ -29,6 +29,10 @@ namespace Nz
 			virtual ViewerInstance& GetViewerInstance() = 0;
 			virtual const ViewerInstance& GetViewerInstance() const = 0;
 			virtual const Recti& GetViewport() const = 0;
+
+			Vector3f Project(const Vector3f& worldPos);
+
+			Vector3f Unproject(const Vector3f& screenPos);
 	};
 }
 
diff --git a/src/Nazara/Graphics/AbstractViewer.cpp b/src/Nazara/Graphics/AbstractViewer.cpp
index baa6e4aae..1788793c5 100644
--- a/src/Nazara/Graphics/AbstractViewer.cpp
+++ b/src/Nazara/Graphics/AbstractViewer.cpp
@@ -3,9 +3,46 @@
 // For conditions of distribution and use, see copyright notice in Config.hpp
 
 #include <Nazara/Graphics/AbstractViewer.hpp>
+#include <Nazara/Graphics/ViewerInstance.hpp>
+#include <Nazara/Renderer/RenderTarget.hpp>
 #include <Nazara/Graphics/Debug.hpp>
 
 namespace Nz
 {
-    AbstractViewer::~AbstractViewer() = default;
+	AbstractViewer::~AbstractViewer() = default;
+
+	Vector3f AbstractViewer::Project(const Vector3f& worldPos)
+	{
+		const Matrix4f& viewProj = GetViewerInstance().GetViewProjMatrix();
+		Vector2f screenSize = Vector2f(GetRenderTarget().GetSize());
+
+		Vector4f clipspace = viewProj * Vector4f(worldPos, 1.f);
+		clipspace.x = clipspace.x / clipspace.w;
+		clipspace.y = clipspace.y / clipspace.w;
+		clipspace.z = clipspace.z / clipspace.w;
+
+		Vector3f screenSpace;
+		screenSpace.x = (clipspace.x * 0.5f + 0.5f) * screenSize.x;
+		screenSpace.y = (clipspace.y * 0.5f + 0.5f) * screenSize.y;
+		screenSpace.z = clipspace.z;
+
+		return screenSpace;
+	}
+
+	Vector3f AbstractViewer::Unproject(const Vector3f& screenPos)
+	{
+		const Matrix4f& inverseViewProj = GetViewerInstance().GetInvViewProjMatrix();
+		Vector2f screenSize = Vector2f(GetRenderTarget().GetSize());
+
+		// Screen space => clip space
+		Vector4f clipSpace;
+		clipSpace.x = screenPos.x / screenSize.x * 2.f - 1.f;
+		clipSpace.y = screenPos.y / screenSize.y * 2.f - 1.f;
+		clipSpace.z = screenPos.z;
+		clipSpace.w = 1.f;
+
+		// Clip space => projection space => view space => world space
+		Vector4f unproj = inverseViewProj * clipSpace;
+		return Vector3f(unproj.x, unproj.y, unproj.z) / unproj.w;
+	}
 }