From 61578d1ddb63b57dadb7e5c044e959ce65435ab8 Mon Sep 17 00:00:00 2001
From: Philip Rosedale <philip@coffeeandpower.com>
Date: Fri, 26 Apr 2013 09:59:50 -0700
Subject: [PATCH] Added balls class

---
 interface/src/Balls.cpp | 106 ++++++++++++++++++++++++++++++++++++++++
 interface/src/Balls.h   |  37 ++++++++++++++
 2 files changed, 143 insertions(+)
 create mode 100644 interface/src/Balls.cpp
 create mode 100644 interface/src/Balls.h

diff --git a/interface/src/Balls.cpp b/interface/src/Balls.cpp
new file mode 100644
index 0000000000..82f59c025f
--- /dev/null
+++ b/interface/src/Balls.cpp
@@ -0,0 +1,106 @@
+//
+//  Balls.cpp
+//  hifi
+//
+//  Created by Philip on 4/25/13.
+//
+//  A cloud of spring-mass spheres to simulate the avatar body/skin.  Each ball
+//  connects to as many as 4 neighbors, and executes motion according to a damped
+//  spring, while responding physically to other avatars.   
+//  
+
+#include "Balls.h"
+
+Balls::Balls(int numberOfBalls) {
+    _numberOfBalls = numberOfBalls;
+    _balls = new Ball[_numberOfBalls];
+    for (unsigned int i = 0; i < _numberOfBalls; ++i) {
+        _balls[i].position = glm::vec3(1.0 + randFloat()*0.5,
+                                       0.5 + randFloat()*0.5,
+                                       1.0 + randFloat()*0.5);
+        _balls[i].radius = 0.02 + randFloat()*0.06;
+        for (unsigned int j = 0; j < NUMBER_SPRINGS; ++j) {
+            _balls[i].links[j] = rand() % (numberOfBalls + 1);
+            if (_balls[i].links[j]-1 == i) { _balls[i].links[j] = 0; }
+            _balls[i].springLength[j] = 0.5;
+         }
+    }
+}
+
+const bool RENDER_SPRINGS = true;
+
+void Balls::render() {
+    
+    //  Render Balls    NOTE:  This needs to become something other that GlutSpheres!
+    glColor3f(0.62,0.74,0.91);
+    for (unsigned int i = 0; i < _numberOfBalls; ++i) {
+        glPushMatrix();
+        glTranslatef(_balls[i].position.x, _balls[i].position.y, _balls[i].position.z);
+        glutSolidSphere(_balls[i].radius, 15, 15);
+        glPopMatrix();
+    }
+    
+    //  Render springs
+    if (RENDER_SPRINGS) {
+        glColor3f(0.74,0.91,0.62);
+        for (unsigned int i = 0; i < _numberOfBalls; ++i) {
+            glBegin(GL_LINES);
+            for (unsigned int j = 0; j < NUMBER_SPRINGS; ++j) {
+                if(_balls[i].links[j] > 0) {
+                    glVertex3f(_balls[i].position.x,
+                               _balls[i].position.y,
+                               _balls[i].position.z);
+                    glVertex3f(_balls[_balls[i].links[j]-1].position.x,
+                               _balls[_balls[i].links[j]-1].position.y,
+                               _balls[_balls[i].links[j]-1].position.z);
+                }
+            }
+            glEnd();
+        }
+    }
+     
+}
+
+const float CONSTANT_VELOCITY_DAMPING = 1.0f;
+const float NOISE_SCALE = 0.00;
+const float SPRING_FORCE = 1.0;
+const float SPRING_DAMPING = 1.0;
+
+void Balls::simulate(float deltaTime) {
+    for (unsigned int i = 0; i < _numberOfBalls; ++i) {
+        
+        // Move particles
+        _balls[i].position += _balls[i].velocity * deltaTime;
+        
+        // Drag: decay velocity
+        _balls[i].velocity *= (1.f - CONSTANT_VELOCITY_DAMPING*deltaTime);
+        
+        // Add noise
+        _balls[i].velocity += glm::vec3((randFloat() - 0.5) * NOISE_SCALE,
+                                        (randFloat() - 0.5) * NOISE_SCALE,
+                                        (randFloat() - 0.5) * NOISE_SCALE);
+        
+        // Spring Force
+        
+        
+        for (unsigned int j = 0; j < NUMBER_SPRINGS; ++j) {
+            if(_balls[i].links[j] > 0) {
+                float separation = glm::distance(_balls[i].position,
+                                                _balls[_balls[i].links[j]-1].position);
+                _balls[i].velocity += glm::normalize(_balls[i].position -
+                                                   _balls[_balls[i].links[j]-1].position) *
+                                        deltaTime *
+                                        SPRING_FORCE *
+                                        (_balls[i].springLength[j] - separation);
+                
+                //_balls[i].velocity *= (1.f - SPRING_DAMPING*deltaTime);
+
+            }
+        }
+         
+         
+        
+
+    }
+}
+
diff --git a/interface/src/Balls.h b/interface/src/Balls.h
new file mode 100644
index 0000000000..653854a0c6
--- /dev/null
+++ b/interface/src/Balls.h
@@ -0,0 +1,37 @@
+//
+//  Balls.h
+//  hifi
+//
+//  Created by Philip on 4/25/13.
+//
+//
+
+#ifndef hifi_Balls_h
+#define hifi_Balls_h
+
+#include <glm/glm.hpp>
+#include "Util.h"
+#include "world.h"
+#include "InterfaceConfig.h"
+
+
+const int NUMBER_SPRINGS = 4;
+
+class Balls {
+public:
+    Balls(int numberOfBalls);
+    
+    void simulate(float deltaTime);
+    void render();
+    
+private:
+    struct Ball {
+        glm::vec3   position, velocity;
+        int         links[NUMBER_SPRINGS];
+        float       springLength[NUMBER_SPRINGS];
+        float       radius;
+    } *_balls;
+    int _numberOfBalls;
+};
+
+#endif