Diff: bouncing_ball.cpp

Revision:

2:ba1844b0eb9f

Parent:

1:0aa572c0f2b1

Child:

3:30b5a3adc15f

--- a/bouncing_ball.cpp	Tue Oct 24 12:33:39 2017 +0000
+++ b/bouncing_ball.cpp	Tue Nov 07 12:07:13 2017 +0000
@@ -1,56 +1,95 @@
 #include "mbed.h"
 #include "bouncing_ball.h"
 
-physics_ball::physics_ball(int color_in, int radius_in)
+//Constructor.  Default values are set in the library header for all member variables.
+physics_ball::physics_ball()
 {
+    // Set all values to defaults defined above (avoids magic numbers)!
     speedx = DEFAULT_SPEEDX;
     speedy = DEFAULT_SPEEDY;
     posx = DEFAULT_POSX;
     posy = DEFAULT_POSY;
-    color = color_in;
-    radius = radius_in;
+    color = DEFAULT_COLOR;
+    radius = DEFAULT_RADIUS;
+    _width = DEFAULT_WIDTH;
+    _height = DEFAULT_HEIGHT;
+    _posy_f = (float) posx;
+    _posx_f = (float) posy;
 }
 
+//Deconstructor exists, but does nothing.
 physics_ball::~physics_ball()
 {
 }
 
-void physics_ball::define_space(int width, int height)
+//Provides the ability to reset the size of the space that the ball is bouncing in.
+//Width and height do noy have to be the same size as the LCD screen.
+void physics_ball::define_space(int desired_width, int desired_height)
 {
-    space_width = width;
-    space_height = height;
+    _width = desired_width;
+    _height = desired_height;
 }
 
-void physics_ball::set_param(int radius_in, int color_in)
+//An alternative means of setting desired radius and colored.
+void physics_ball::set_param(int desired_radius, int desired_color)
 {
-    radius = radius_in;
-    color = color_in;
+    radius = desired_radius;
+    color = desired_color;
 }
 
-void physics_ball::set_state(int x, int y, float vx, float vy)
+//An alternative means of setting desired positions and velocities.
+void physics_ball::set_state(int desired_x, int desired_y, float desired_vx, float desired_vy)
 {
-    posx = x;
-    posy = y;
-    speedx = vx;
-    speedy = vy;
+    posx = desired_x;
+    posy = desired_y;
+    _posx_f = (float) posx;
+    _posy_f = (float) posy;
+    speedx = desired_vx;
+    speedy = desired_vy;
 }
 
-void physics_ball::update(float time_step, MMA8452Q accelerometer)
+//The heart of the matter: the calculation used to update the position of a ball
+//using inputs from an accelerometer.
+void physics_ball::update(float time_step, MMA8452Q& accelerometer)
 {
+    //If upside down, hold ball still.
+    if (accelerometer.readZ() < 0) {
+        if (_upside_down_status == 0) {
+            _reset_upside_down();
+            _upside_down_status = 1;
+        }
+    } else {
+        _upside_down_status = 0;
 
-    // Move circle. IMPORTANT! Notice how we adjust for sensor orientation!
-    posx -= (speedx * accelerometer.readY());
-    posy -= (speedy * accelerometer.readX());
+        // Make circle bounce off of edges if at the edges:
+        if (( posx <= radius) || ((posx + radius) >= _width)) {
+            speedx = -speedx;
+        }
+        if (( posy <= radius) || ((posy + radius) >= _height)) {
+            speedy = -speedy;
+        }
 
-    // Make circle sit on edges
-    if ( posx <= radius + 1 ) {
-        posx = radius + 1;
-    } else if ( posx >= space_width - radius ) {
-        posx = space_width - radius;
+        //Accelerate per actual real world physics:
+        speedx -= GRAVITY * accelerometer.readY(); //* time_step;
+        speedy -= GRAVITY * accelerometer.readX(); //* time_step;
+
+        //Position update depends on speed:
+        _posx_f = _posx_f + speedx * time_step;
+        _posy_f = _posy_f + speedy * time_step;
+        
+        //Actual position has to be able to update in less than integer increments.
+        //Report out position is expected in integers, however.
+        posx = (int) _posx_f;
+        posy = (int) _posy_f;
     }
-    if ( posy <= radius + 1 ) {
-        posy = radius + 1;
-    } else if ( posy >= space_height - radius ) {
-        posy = space_height - radius;
+}
+
+void physics_ball::_reset_upside_down()
+{
+    //Increment color when the accelerometer turned upside down.
+    //It's up to the main code to interpret the color.
+    color += 1;
+    if (color > 3) {
+        color = 0;
     }
 }
\ No newline at end of file