From bcf93bb4ce331c1cc2a85f9444d6d90323f8433c Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Sun, 3 Aug 2014 18:51:49 -0700
Subject: [PATCH] LookAt comments

---
 src/camera.cc | 9 +++++++++
 src/camera.h  | 5 +++++
 2 files changed, 14 insertions(+)

diff --git a/src/camera.cc b/src/camera.cc
index 31cb36c..d064f16 100644
--- a/src/camera.cc
+++ b/src/camera.cc
@@ -97,6 +97,10 @@ Camera::SetUp(const Vector3& up)
 void
 Camera::LookAt(const Vector3& pt)
 {
+    /*
+     * Precalulate these in order to preserve the aspect ratio and orientation
+     * of the camera across the LookAt operation.
+     */
     const Double directionLength = mDirection.length();
     const Double rightLength = mRight.length();
     const Double upLength = mUp.length();
@@ -106,6 +110,11 @@ Camera::LookAt(const Vector3& pt)
     mDirection = (pt - mOrigin).normalize();
     /* TODO: Check for zero length direction vector. */
 
+    /*
+     * TODO: This is always the Y vector. POV-Ray has a sky vector, which
+     * specifies the vector along which LookAt pans and tilts the camera. It
+     * might be worth looking into, at some point.
+     */
     mRight = Vector3::Y.cross(mDirection).normalize();
     mUp = mDirection.cross(mRight);
 
diff --git a/src/camera.h b/src/camera.h
index a18e461..8008be6 100644
--- a/src/camera.h
+++ b/src/camera.h
@@ -35,6 +35,11 @@ struct Camera
     const Vector3& GetUp() const;
     void SetUp(const Vector3& up);
 
+    /**
+     * Pan and tilt the camera towards the given point.
+     *
+     * @param [in] pt   The point at which to face the camera
+     */
     void LookAt(const Vector3& pt);
 
     virtual Ray compute_primary_ray(const int x, const int width,