Added GetScreenDirection function to Chapter 9

Author: chalonverse

Chapter09/Renderer.cpp

@@ -324,3 +324,16 @@ Vector3 Renderer::Unproject(const Vector3& screenPoint) const
 	unprojection.Invert();
 	return Vector3::TransformWithPerspDiv(deviceCoord, unprojection);
 }
+
+void Renderer::GetScreenDirection(Vector3& outStart, Vector3& outDir) const
+{
+	// Get start point (in center of screen on near plane)
+	Vector3 screenPoint(0.0f, 0.0f, 0.0f);
+	outStart = Unproject(screenPoint);
+	// Get end point (in center of screen, between near and far)
+	screenPoint.z = 0.9f;
+	Vector3 end = Unproject(screenPoint);
+	// Get direction vector
+	outDir = end - outStart;
+	outDir.Normalize();
+}

Chapter09/Renderer.h

@@ -56,6 +56,7 @@ class Renderer
 	// y = [-screenHeight/2, +screenHeight/2]
 	// z = [0, 1) -- 0 is closer to camera, 1 is further
 	Vector3 Unproject(const Vector3& screenPoint) const;
+	void GetScreenDirection(Vector3& outStart, Vector3& outDir) const;
 	float GetScreenWidth() const { return mScreenWidth; }
 	float GetScreenHeight() const { return mScreenHeight; }
 private: