Switched to quaternion rotations to avoid drift

src/Camera.cpp

@@ -49,8 +49,33 @@ void Camera::translate(vec3 v) {
   this->target += v; // keep the view direction constant
 }
 
-// axis-angle rotation
 void Camera::rotate(vec3 v) {
+  this->rotateQuat(v);
+  //this->rotateAxisAngle(v); // to change easily
+}
+
+// quaternion rotation
+void Camera::rotateQuat(vec3 v) {
+  v = -v;
+  float angle = length(v);
+  vec3 w = normalize(v);
+
+  glm::quat viewDir (0, normalize(this->getViewDir()));
+  viewDir = glm::rotate(viewDir, angle, w);
+
+  glm::quat upDir (0, normalize(this->getUpDir()));
+  upDir = glm::rotate(upDir, angle, w);
+  
+  vec3 u = axis(viewDir);
+  this->up = axis(upDir);
+
+  vec3 view = this->target - this->position;
+  this->target = this->position + u*length(view);
+}
+
+// axis-angle (exponential map) rotation
+// doesn't have SLERP, so a more noticeable drift occurs
+void Camera::rotateAxisAngle(vec3 v) {
   float angle = length(v);
   vec3 w = normalize(v);
   vec3 a = this->getViewDir();

src/Camera.h

@@ -7,7 +7,9 @@
 #ifndef CAMERA_H
 #define CAMERA_H
 
+#define GLM_FORCE_RADIANS
 #include <glm/glm.hpp>
+#include <glm/gtc/quaternion.hpp>
 
 using namespace glm;
 
@@ -24,6 +26,9 @@ class Camera {
   void translate(vec3 v);
   void rotate(vec3 v);
 
+  void rotateAxisAngle(vec3 v);
+  void rotateQuat(vec3 v);
+
  private:
   vec3 position;
   vec3 target;

src/main.cpp

@@ -52,7 +52,7 @@ void initGlobals() {
 
   // globals
   globals.translate_step = 0.05f;
-  globals.rotate_step = 0.01f;
+  globals.rotate_step = 0.03f;
   globals.mousex = viewport.width/2.0;
   globals.mousey = viewport.height/2.0;
 }
@@ -116,7 +116,7 @@ void moveCamera() {
   glm::vec3 right = glm::cross(forward,up);
 
   float epsilon = 0.001f;
-  float scale = 2000.0f;
+  float scale = 1000.0f;
 
   // mouse
   double xpos, ypos;