camera.h

#pragma once

#include <glm/ext.hpp>
#include <glm/glm.hpp>

/* A simple arcball camera that moves around the camera's focal point.
 * The mouse inputs to the camera should be in normalized device coordinates,
 * where the top-left of the screen corresponds to [-1, 1], and the bottom
 * right is [1, -1].
 */
class ArcballCamera {
    // We store the unmodified look at matrix along with
    // decomposed translation and rotation components
    glm::mat4 mTranslation;
    glm::mat4 mRotation;
    glm::vec3 rotVec;
    // camera is the full camera transform,
    // inv_camera is stored as well to easily compute
    // eye position and world space rotation axes
    glm::mat4 camera, inv_camera;

public:
    /* Create an arcball camera focused on some center point
     * screen: [win_width, win_height]
     */
    ArcballCamera(const glm::vec3 &eye, const glm::vec3 &center, const glm::vec3 &up);

    /* Rotate the camera from the previous mouse position to the current
     * one. Mouse positions should be in normalized device coordinates
     */
    void rotate(glm::vec2 prev_mouse, glm::vec2 cur_mouse);

    /* Pan the camera given the translation vector. Mouse
     * delta amount should be in normalized device coordinates
     */
    void pan(glm::vec2 mouse_delta);

    /* Zoom the camera given the zoom amount to (i.e., the scroll amount).
     * Positive values zoom in, negative will zoom out.
     */
    void zoom(const float zoom_amount);

    // Get the camera transformation matrix
    const glm::mat4 &transform() const;

    // Get the camera's inverse transformation matrix
    const glm::mat4 &inv_transform() const;

    // Get the eye position of the camera in world space
    glm::vec3 eye() const;

    // Get the eye direction of the camera in world space
    glm::vec3 dir() const;

    // Get the up direction of the camera in world space
    glm::vec3 up() const;

private:
    void update_camera();
};