Big bang

src/arc_ball.h

@@ -0,0 +1,100 @@
+#ifndef ARCBALL_H
+#define ARCBALL_H
+
+#include <Magnum/Magnum.h>
+#include <Magnum/Math/DualQuaternion.h>
+#include <Magnum/Math/Functions.h>
+#include <Magnum/Math/Vector2.h>
+#include <Magnum/Math/Vector3.h>
+
+using namespace Magnum;
+
+Quaternion ndcToArcBall(const Vector2 &p);
+
+/* Implementation of Ken Shoemake's arcball camera with smooth navigation
+   feature: https://www.talisman.org/~erlkonig/misc/shoemake92-arcball.pdf */
+class ArcBall {
+public:
+  ArcBall(const Vector3 &cameraPosition, const Vector3 &viewCenter,
+          const Vector3 &upDir, Deg fov, const Vector2i &windowSize);
+
+  /* Set the camera view parameters: eye position, view center, up
+     direction */
+  void setViewParameters(const Vector3 &eye, const Vector3 &viewCenter,
+                         const Vector3 &upDir);
+
+  /* Reset the camera to its initial position, view center, and up dir */
+  void reset();
+
+  /* Update screen size after the window has been resized */
+  void reshape(const Vector2i &windowSize) { m_windowSize = windowSize; }
+
+  /* Update any unfinished transformation due to lagging, return true if
+     the camera matrices have changed */
+  bool updateTransformation();
+
+  /* Get/set the amount of lagging such that the camera will (slowly)
+     smoothly navigate. Lagging must be in [0, 1) */
+  Float lagging() const { return m_lagging; }
+  void setLagging(Float lagging);
+
+  /* Initialize the first (screen) mouse position for camera
+     transformation. This should be called in mouse pressed event. */
+  void initTransformation(const Vector2i &mousePos);
+
+  /* Rotate the camera from the previous (screen) mouse position to the
+     current (screen) position */
+  void rotate(const Vector2i &mousePos);
+
+  /* Translate the camera from the previous (screen) mouse position to
+     the current (screen) mouse position */
+  void translate(const Vector2i &mousePos);
+
+  /* Translate the camera by the delta amount of (NDC) mouse position.
+     Note that NDC position must be in [-1, -1] to [1, 1]. */
+  void translateDelta(const Vector2 &translationNDC);
+
+  /* Zoom the camera (positive delta = zoom in, negative = zoom out) */
+  void zoom(Float delta);
+
+  /* Get the camera's view transformation as a qual quaternion */
+  const DualQuaternion &view() const { return m_view; }
+
+  /* Get the camera's view transformation as a matrix */
+  Matrix4 viewMatrix() const { return m_view.toMatrix(); }
+
+  /* Get the camera's inverse view matrix (which also produces
+     transformation of the camera) */
+  Matrix4 inverseViewMatrix() const { return m_inverseView.toMatrix(); }
+
+  /* Get the camera's transformation as a dual quaternion */
+  const DualQuaternion &transformation() const { return m_inverseView; }
+
+  /* Get the camera's transformation matrix */
+  Matrix4 transformationMatrix() const { return m_inverseView.toMatrix(); }
+
+  /* Return the distance from the camera position to the center view */
+  Float viewDistance() const { return Math::abs(m_targetZooming); }
+
+protected:
+  /* Update the camera transformations */
+  void updateInternalTransformations();
+
+  /* Transform from screen coordinate to NDC - normalized device
+     coordinate. The top-left of the screen corresponds to [-1, 1] NDC,
+     and the bottom right is [1, -1] NDC. */
+  Vector2 screenCoordToNDC(const Vector2i &mousePos) const;
+
+  Deg m_fov;
+  Vector2i m_windowSize;
+
+  Vector2 m_prevMousePosNDC;
+  Float m_lagging{};
+
+  Vector3 m_targetPosition, m_currentPosition, m_positionT0;
+  Quaternion m_targetQRotation, m_currentQRotation, m_qRotationT0;
+  Float m_targetZooming, m_currentZooming, m_zoomingT0;
+  DualQuaternion m_view, m_inverseView;
+};
+
+#endif