TrackballCamera.h

// Trackball Camera class
// Written by Sergey Kosov in 2016 for Project X
#pragma once

#include "glm/glm.hpp"
#include "glm/gtc/matrix_transform.hpp"

namespace DirectGraphicalModels { namespace vis
{
    // ================================ Trackball Camera  Class ===============================
    class CTrackballCamera
    {
    public:
        CTrackballCamera(float theta, float phi, float radius)
            : m_initTheta(theta)
            , m_initPhi(phi)
            , m_initRadius(radius)
            , m_theta(theta)
            , m_phi(phi)
            , m_radius(radius)
            , m_up(phi >= 0 ? 1.0f : -1.0f)
            , m_target(0)
            , m_view(glm::mat4(1))
            , m_viewNeedsUpdate(true)
        { }
        virtual ~CTrackballCamera(void) {}

        void        reset(void);
        glm::mat4   getViewMatrix(void);


    protected:
        void        rotate(float dTheta, float dPhi);
        void        zoom(float dRadius);
        void        pan(float dx, float dy);

        glm::vec3   getCameraOrintation(void) const { return glm::vec3(sinf(m_phi) * sinf(m_theta), cosf(m_phi), sinf(m_phi) * cosf(m_theta)); }
        glm::vec3   getCameraPosition(void) const { return m_target + getCameraOrintation() * m_radius; }
        void        updateViewMatrix(void) { m_view = glm::lookAt(getCameraPosition(), m_target, glm::vec3(0, m_up, 0)); }


    private:
        float       m_initTheta;
        float       m_initPhi;
        float       m_initRadius;
        float       m_theta;
        float       m_phi;
        float       m_radius;
        float       m_up;

        glm::vec3   m_target;
        glm::mat4   m_view;

        bool        m_viewNeedsUpdate;
    };

} }