From 188d43cb5036c10a6fc16c4798edae02304fef43 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9mi=20Oudin?= <oudin@crans.org>
Date: Tue, 13 Feb 2018 10:51:07 +0100
Subject: [PATCH] Better animation

Bounces are slower, final position is the ball undeformed.
Also, moves continuously when it keep staying on the ground.
---
 Ball.cpp | 27 ++++++++++++++++++++++++---
 Ball.hpp |  1 +
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/Ball.cpp b/Ball.cpp
index 0593040..9cef020 100644
--- a/Ball.cpp
+++ b/Ball.cpp
@@ -2,10 +2,14 @@
 #include <iostream>
 #include <cmath>
 
+bool bouncing = true;
+double stop_bouncing;
+
 Ball::Ball(const Point& _center, double _min_height, double _v_x, double _v_z,
         double _p, double _q) :
     Center(_center),
     surface(_center, _min_height, _p, _q),
+    radius(_p),
     init_h(_center.y),
     min_height(_min_height),
     bounce_number(0.0),
@@ -20,7 +24,16 @@ Ball::Ball(const Point& _center, double _min_height, double _v_x, double _v_z,
 }
 
 void Ball::_compute_pos(double dt) {
-    Center.y = fmax(0.0, A + B * crt_time - (G_CTE / 2) * crt_time * crt_time + min_height);
+    if (bouncing) {
+        Center.y = fmax(
+            min_height,
+            A + B * crt_time - (G_CTE / 2) * crt_time * crt_time + min_height
+        );
+    } else {
+        double n_time = crt_time - stop_bouncing;
+        Center.y = ((radius * (1.0 - exp(-n_time)) + radius)/2.) + (radius -
+                ((radius * (1- exp(-n_time)) + radius)/2.)) * sin(5. * n_time);
+    }
     Center.x += dt * v_x;
     Center.z += dt * v_z;
     surface.update_center_pos(Center);
@@ -28,7 +41,7 @@ void Ball::_compute_pos(double dt) {
 }
 
 void Ball::_compute_T_n() {
-    double update = (pow(0.5, bounce_number-1) * sqrt(2 * init_h / G_CTE));
+    double update = (2. * U / G_CTE);
     T += update;
 }
 void Ball::_compute_B_n() {
@@ -40,7 +53,7 @@ void Ball::_compute_A_n() {
 }
 
 void Ball::_compute_U_n() {
-    U *= 0.5;
+    U *= 0.8;
 }
 
 void Ball::_compute_v_x(Point normal) {
@@ -56,6 +69,8 @@ void Ball::_compute_v_z(Point normal) {
 void Ball::update_pos(double dt) {
     crt_time += dt;
     if (crt_time >= T) {
+        double old_t = T;
+        double max_t;
         Point normal = surface.getNormalVector();
         bounce_number += 1;
         _compute_U_n();
@@ -64,6 +79,12 @@ void Ball::update_pos(double dt) {
         _compute_T_n();
         _compute_v_x(normal);
         _compute_v_z(normal);
+        max_t = (T - old_t)/2.0 + old_t;
+
+        if ((bouncing) && ((A + B * max_t - (G_CTE / 2) * max_t * max_t + min_height) < radius)) {
+            stop_bouncing = crt_time;
+            bouncing = false;
+        }
         std::cout << "New bounce :";
         std::cout << "U:" << U << ":";
         std::cout << "A:" << A << ":";
diff --git a/Ball.hpp b/Ball.hpp
index 60ed9bc..fc26bb1 100644
--- a/Ball.hpp
+++ b/Ball.hpp
@@ -19,6 +19,7 @@ class Ball {
     private:
         Point Center;
         Spheroid surface;
+        double radius;
         double init_h;
         double min_height;
         size_t bounce_number;