Allow the camera to follow the ball

But when the ground is not textured, this looks just as if the ball was
not moving… :(

main_bounce.cpp

@@ -52,8 +52,10 @@ int main(int argc, char** argv) {
         ground_mesh.get_mesh()->set_color(Color(0.13, 0.82, 0.21));
         render.add_mesh(ground_mesh.get_mesh());
     }
+    //render.follow_implicit_position(ball.get_surface());
 
     render.set_idle_func(periodic_update);
+    render.add_kb_handler(periodic_kb_handler);
     init_periodic_static(&ball);
     render.run();
 

periodic_updates.cpp

@@ -8,6 +8,9 @@ static Ball* _ball = nullptr;
 static std::chrono::time_point<std::chrono::steady_clock>
     _last_time, _init_clocks;
 
+static bool is_paused = false;
+static double speed_factor = 1.;
+
 void init_periodic_static(Ball* ball) {
     _last_time = std::chrono::steady_clock::now();
     _init_clocks = std::chrono::steady_clock::now();
@@ -23,9 +26,32 @@ double ellapsed_double(
 }
 
 void periodic_update() {
+    if(is_paused)
+        return;
+
+    printf("%lf\n", speed_factor);
     auto now = std::chrono::steady_clock::now();
-    _ball->update_pos(ellapsed_double(_last_time, now));
+    _ball->update_pos(speed_factor * ellapsed_double(_last_time, now));
 
     _last_time = now;
     glutPostRedisplay();
 }
+
+void periodic_kb_handler(unsigned char key, int, int) {
+    if(key == ' ') {
+        if(is_paused)
+            _last_time = std::chrono::steady_clock::now();
+        is_paused = !is_paused;
+    }
+    else if(key == '<') {
+        speed_factor -= .1;
+        if(speed_factor <= 0.05)
+            speed_factor = .1;
+    }
+    else if(key == '>') {
+        speed_factor += .1;
+    }
+    else if(key == '0') {
+        speed_factor = 1.;
+    }
+}

periodic_updates.hpp

@@ -4,3 +4,5 @@
 
 void init_periodic_static(Ball* ball);
 void periodic_update();
+
+void periodic_kb_handler(unsigned char key, int, int);

render/GlutRender.cpp

@@ -12,7 +12,7 @@ GlutRender& GlutRender::get_instance() {
     return instance;
 }
 
-GlutRender::GlutRender() {
+GlutRender::GlutRender() : followed_implicit(nullptr) {
     std::default_random_engine rand_engine(time(NULL));
     std::uniform_real_distribution<double> distribution;
     rand_color = std::bind(distribution, rand_engine);
@@ -29,6 +29,7 @@ void GlutRender::init(int* argc, char** argv,
     // ==== Callbacks ====
     glutDisplayFunc(display_handle);
     glutReshapeFunc(reshape_handle);
+    glutKeyboardFunc(kb_evt_handle);
 
     // ==== Lighting ====
     GLfloat light0_pos[] = {30., 35., 20., 0.};
@@ -92,6 +93,14 @@ void GlutRender::set_idle_func(void (*func)(void)) {
     glutIdleFunc(func);
 }
 
+void GlutRender::add_kb_handler(GlutRender::kb_handler_t handler) {
+    kb_handlers.push_back(handler);
+}
+
+void GlutRender::follow_implicit_position(const ImplicitSurface* surf) {
+    followed_implicit = surf;
+}
+
 void GlutRender::reshape(int wid, int hei) {
     if (hei == 0)
         hei = 1;
@@ -182,10 +191,19 @@ void GlutRender::display() {
 
     // Camera position and orientation
     glLoadIdentity();
-    //glTranslatef(1., 2., -10.);
-    gluLookAt(0, 2.5, -10,
+
+    Point look_from(0, 2.5, -10);
+    if(followed_implicit != nullptr) {
+        const Point& look_at = followed_implicit->getCenter();
+        gluLookAt(look_from.x, look_from.y, look_from.z,
+                look_at.x, look_from.y, look_at.z,
+                0, 1, 0);
+    }
+    else {
+        gluLookAt(look_from.x, look_from.y, look_from.z,
                 0, 2.5, 0,
                 0, 1, 0);
+    }
 
     for(Mesh* mesh: meshes) {
         display_mesh(*mesh);
@@ -202,9 +220,18 @@ void GlutRender::display() {
     glutSwapBuffers();
 }
 
+void GlutRender::on_kb_evt(unsigned char key, int x, int y) {
+    for(auto& handler: kb_handlers) {
+        handler(key, x, y);
+    }
+}
+
 void GlutRender::reshape_handle(int wid, int hei) {
     get_instance().reshape(wid, hei);
 }
 void GlutRender::display_handle() {
     get_instance().display();
 }
+void GlutRender::kb_evt_handle(unsigned char key, int x, int y) {
+    get_instance().on_kb_evt(key, x, y);
+}

render/GlutRender.hpp

@@ -5,9 +5,12 @@
 #include "../Mesh.hpp"
 #include "../Implicit.hpp"
 #include <set>
+#include <functional>
 
 class GlutRender {
     public:
+        typedef std::function<void(unsigned char, int, int)> kb_handler_t;
+
         static GlutRender& get_instance();
 
         GlutRender(GlutRender const&) = delete;
@@ -25,6 +28,10 @@ class GlutRender {
 
         void set_idle_func(void (*func)(void));
 
+        void add_kb_handler(kb_handler_t handler);
+
+        void follow_implicit_position(const ImplicitSurface* surf);
+
     private:
         struct SurfaceDetails {
             SurfaceDetails(ImplicitSurface* surf, const Cuboid& box,
@@ -49,13 +56,20 @@ class GlutRender {
     protected:
         void reshape(int wid, int hei);
         void display();
+        void on_kb_evt(unsigned char key, int x, int y);
 
         static void reshape_handle(int wid, int hei);
         static void display_handle();
 
+        static void kb_evt_handle(unsigned char key, int x, int y);
+
     private: //attr
         std::function<double()> rand_color;
 
         std::set<Mesh*> meshes;
         std::set<SurfaceDetails> surfaces;
+
+        std::vector<kb_handler_t> kb_handlers;
+
+        const ImplicitSurface* followed_implicit;
 };