From 0f0a35339723e5dc67d2e519f606e5854cfb9e96 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Sat, 19 Jun 2021 23:17:49 +0200
Subject: Tidy up camera rotation

---
 lbm.org | 65 +++++++++++++++++++++++++----------------------------------------
 1 file changed, 25 insertions(+), 40 deletions(-)

(limited to 'lbm.org')

diff --git a/lbm.org b/lbm.org
index c953031..ac99324 100644
--- a/lbm.org
+++ b/lbm.org
@@ -4491,13 +4491,11 @@ a orbiting camera. This type of camera can be rotated around a central target po
 
 While translation is realized easily by adding a shift vector to the current camera position, rotation
 is more complex. We are going to accumulate all rotation operations in a single quaternion variable
-=_rotation=. This 4D vector is easily converted into a rotation matrix for mapping the screen space
-pinhole parameters into world space.
+=_rotation=. Given 3D vectors $v$ are easily rotated by a quaternion $q$ using $v^\prime = q v \overline{q}$.
 
 #+NAME: camera-spherical-coordinates
 #+BEGIN_SRC cpp
 glm::quat _rotation;
-glm::mat3 _matrix;
 #+END_SRC
 
 Using the rotation matrix we can compute the pinhole camera parameters. As they only change
@@ -4505,27 +4503,22 @@ when a rotation is performed we store them in a set of variables.
 
 #+NAME: camera-cartesian-coordinates
 #+BEGIN_SRC cpp
-float3 _target;
-float3 _position;
-float3 _forward;
-float3 _right;
-float3 _up;
+glm::vec3 _target;
+glm::vec3 _position;
+glm::vec3 _forward;
+glm::vec3 _right;
+glm::vec3 _up;
 float _distance;
 #+END_SRC
 
-The =update= function projects the screen space forward, right and up vectors into world space
-by simply multiplying them by the rotation matrix. 
+The =update= function projects the screen space forward, right and up vectors into world space.
 
 #+NAME: camera-projection
 #+BEGIN_SRC cpp :eval no :main no
-glm::vec3 position = _matrix * glm::vec3(0, _distance, 0);
-_position = _target + make_float3(position[0], position[1], position[2]);
-_forward = normalize(_target - _position);
-
-glm::vec3 right = _matrix * glm::vec4(-1, 0, 0, 0);
-_right = make_float3(right[0], right[1], right[2]);
-glm::vec3 up = _matrix * glm::vec4(glm::cross(glm::vec3(0, 1, 0), glm::vec3(-1, 0, 0)), 0);
-_up = make_float3(up[0], up[1], up[2]);
+_position = _target + glm::axis(_rotation * glm::quat(0, 0, _distance, 0) * glm::conjugate(_rotation));
+_forward = glm::normalize(_target - _position);
+_right = glm::axis(_rotation * glm::quat(0, -1, 0, 0) * glm::conjugate(_rotation));
+_up = glm::axis(_rotation * glm::quat(0, glm::cross(glm::vec3(0, 1, 0), glm::vec3(-1, 0, 0))) * glm::conjugate(_rotation));
 #+END_SRC
 
 Finally we need to handle user input events to change the translation vector
@@ -4554,22 +4547,18 @@ case sf::Event::MouseButtonReleased:
   }
   break;
 case sf::Event::MouseMoved:
+  float2 mouse = make_float2(event.mouseMove.x, event.mouseMove.y);
   if (_dragging) {
-    float2 mouse = make_float2(event.mouseMove.x, event.mouseMove.y);
-    float2 delta = mouse - _lastMouse;
-    _lastMouse = mouse;
-
-    glm::quat rotation_z = glm::conjugate(_rotation) * glm::vec3(0,0,0.01*delta.x);
-    glm::quat rotation_x = glm::conjugate(_rotation) * glm::vec3(0.01*delta.y,0,0);
-
-    _matrix = _matrix * glm::mat3_cast(_rotation * glm::cross(rotation_x, rotation_z));
+    float2 delta = 0.005 * (mouse - _lastMouse);
+    glm::quat rotation_z = glm::vec3(0,0,delta.x);
+    glm::quat rotation_x = glm::vec3(delta.y,0,0);
+    _rotation *= glm::cross(rotation_x, rotation_z);
   }
   if (_moving) {
-    float2 mouse = make_float2(event.mouseMove.x, event.mouseMove.y);
-    float2 delta = mouse - _lastMouse;
-    _lastMouse = mouse;
-    _target += 0.4*_right*delta.x + 0.4*_up*delta.y;
+    float2 delta = 0.04 * (mouse - _lastMouse);
+    _target += _right*delta.x + _up*delta.y;
   }
+  _lastMouse = mouse;
   break;
 }
 #+END_SRC
@@ -4587,7 +4576,7 @@ private:
 public:
   Camera(float3 target, float distance):
     _distance(distance),
-    _target(target),
+    _target(target.x, target.y, target.z),
     _dragging(false),
     _moving(false) {
     update();
@@ -4603,28 +4592,24 @@ public:
   }
 
   float3 getPosition() const {
-    return _position;
+    return make_float3(_position.x, _position.y, _position.z);
   }
   float3 getForward() const {
-    return _forward;
+    return make_float3(_forward.x, _forward.y, _forward.z);
   }
   float3 getRight() const {
-    return _right;
+    return make_float3(_right.x, _right.y, _right.z);
   }
   float3 getUp() const {
-    return _up;
+    return make_float3(_up.x, _up.y, _up.z);
   }
 };
 #+END_SRC
 
 #+BEGIN_SRC cpp :tangle tangle/util/camera.h :eval no :main no
 #include <cuda-samples/Common/helper_math.h>
-#include "SFML/Window/Event.hpp"
-
-#include <glm/glm.hpp>
-#include <glm/gtc/quaternion.hpp>
 #include <glm/gtx/quaternion.hpp>
-#include <glm/common.hpp>
+#include "SFML/Window/Event.hpp"
 
 <<camera>>
 #+END_SRC
-- 
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