From f2f60a8c203c668c30e7eef12723a1111f9f97d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Anselme=20FRAN=C3=87OIS?=
 <anselme.francois+gitlab@gmail.com>
Date: Sun, 19 Jun 2016 21:37:19 +0200
Subject: [PATCH] added trackball camera

---
 src/trackballcamera.cpp | 74 +++++++++++++++++++++++++++++++++++++++++
 src/trackballcamera.h   | 43 ++++++++++++++++++++++++
 2 files changed, 117 insertions(+)
 create mode 100644 src/trackballcamera.cpp
 create mode 100644 src/trackballcamera.h

diff --git a/src/trackballcamera.cpp b/src/trackballcamera.cpp
new file mode 100644
index 0000000..35558d4
--- /dev/null
+++ b/src/trackballcamera.cpp
@@ -0,0 +1,74 @@
+#include "trackballcamera.h"
+#include <glm/ext.hpp>
+
+#define SCROLL_SPEED 0.998f
+#define ROTATION_SPEED 0.01f
+#define MOVE_SPEED 0.002f
+
+TrackBallCamera::TrackBallCamera(float myFov, float myNear, float myFar) :
+    m_fov(myFov), m_near(myNear), m_far(myFar)
+{
+    reset();
+    resize(800, 600);
+}
+
+void TrackBallCamera::resize(int width, int height)
+{
+    if(width > 0 && height > 0)
+        m_projection = glm::perspectiveFov<float>(m_fov, float(width), float(height), m_near, m_far);
+}
+
+void TrackBallCamera::rotateCamera(float dx, float dy)
+{
+    m_rotation.x += dx*ROTATION_SPEED;
+    m_rotation.y += dy*ROTATION_SPEED;
+    if(m_rotation.y > 1.57f)
+        m_rotation.y = 1.57f;
+    if(m_rotation.y < -1.57f)
+        m_rotation.y = -1.57f;
+    computeView();
+}
+
+void TrackBallCamera::reset()
+{
+    m_center = glm::vec3(0, 4, 0);
+    m_target = m_center;
+    m_rotation = glm::vec2(0, 1);
+    m_dist = 20;
+    computeView();
+}
+
+void TrackBallCamera::computeView()
+{
+
+    m_view = glm::translate(glm::mat4(), glm::vec3(0, 0, -m_dist));
+    m_view = glm::rotate(m_view, m_rotation.y, glm::vec3(1, 0, 0));
+    m_view = glm::rotate(m_view, m_rotation.x, glm::vec3(0, 1, 0));
+    m_view = glm::translate(m_view, -m_center);
+}
+
+void TrackBallCamera::mouseScroll(int nbScrolls)
+{
+	while(nbScrolls != 0)
+	{
+		if(nbScrolls > 0)
+		{
+			m_dist *= SCROLL_SPEED;
+			--nbScrolls;
+		}
+		else
+		{
+			m_dist /= SCROLL_SPEED;
+			++nbScrolls;
+		}
+	}
+
+	computeView();
+}
+
+glm::vec3 TrackBallCamera::getDefaultPxInfo()
+{
+    glm::vec4 viewPos(m_center, 1);
+    viewPos = (m_projection * m_view) * viewPos;
+    return glm::vec3(m_dist/m_far, 1/viewPos.w, 0);
+}
diff --git a/src/trackballcamera.h b/src/trackballcamera.h
new file mode 100644
index 0000000..7bc0ffa
--- /dev/null
+++ b/src/trackballcamera.h
@@ -0,0 +1,43 @@
+#ifndef TRACKBALLCAMERA_H
+#define TRACKBALLCAMERA_H
+
+#include <camera.h>
+#include <glm/vec2.hpp>
+#include <glm/vec3.hpp>
+
+class TrackBallCamera : public Camera
+{
+    glm::mat4 m_view;
+    glm::mat4 m_projection;
+
+    float m_fov;
+    float m_near;
+    float m_far;
+
+    // camera position
+    glm::vec3 m_center;
+    glm::vec2 m_rotation;
+    float m_dist;
+
+    // camera movement
+    glm::vec3 m_origin;
+    glm::vec3 m_target;
+
+public:
+    TrackBallCamera(float myFov = 70.f, float myNear = 0.1f, float myFar = 1000.f);
+
+    glm::mat4 getProjectionMatrix() {return m_projection;}
+    glm::mat4 getViewMatrix() {return m_view;}
+
+    void resize(int width, int height);
+
+    void rotateCamera(float dx, float dy);
+    void moveCamera(float dx, float dy);
+	void mouseScroll(int nbScrolls);
+    void reset();
+    void computeView();
+    void setCenter(glm::vec3 pos) { m_center = pos; computeView(); }
+    glm::vec3 getDefaultPxInfo();
+};
+
+#endif // TRACKBALLCAMERA_H