#include <stdio.h>#include <stdlib.h>#include <stdarg.h>#include <math.h>#include <memory.h>#include <windows.h>#include <gl/glut.h>#include <vector>#pragma comment(lib, "opengl32.lib")#pragma comment(lib, "glu32.lib")#pragma comment(lib, "glut32.lib")void dbgBreak(){	__asm int 3;}void dbg(const char* format, ...){	va_list args;	va_start(args, format);	char buff[512];	vsprintf_s(buff, sizeof(buff), format, args);	va_end(args);	char str[1024];	sprintf_s(str, sizeof(str), "%s\n", buff);	printf(str);	OutputDebugString(str);}float randf(float range){	return (rand() / (float)(RAND_MAX)) * range;}float randf(float min, float max){	return min + (rand() / (float)(RAND_MAX)) * (max - min);}float twopi(){	static float g_twopi = atan(1.0f) * 8.0f;	return g_twopi;}//===========================================================================// VECTORS//===========================================================================class Vector{public:	float x,y;public:	inline Vector(void)	{}	inline Vector(float ix,float iy)	: x(ix)	, y(iy)	{}	inline Vector &operator /=(const float scalar)	{ x /= scalar; y /= scalar;		return *this; }	inline Vector &operator *=(const float scalar)	{ x *= scalar; y *= scalar;		return *this; }		inline Vector &operator +=(const Vector &other) { x += other.x;	y += other.y;	return *this; }	inline Vector &operator -=(const Vector &other)	{ x -= other.x;	y -= other.y;	return *this;	}	inline float operator ^ (const Vector &other)	const	{	return (x * other.y) - (y * other.x); } // cross product	inline float operator * (const Vector &other)	const	{	return (x * other.x) + (y * other.y); } // dot product	inline Vector operator * (float  scalar)		const	{	return Vector(x * scalar, y * scalar); }		inline Vector operator / (float  scalar)		const	{	return Vector(x / scalar, y / scalar); }		inline Vector operator + (const Vector &other)	const	{	return Vector(x + other.x, y + other.y); }			inline Vector operator - (const Vector &other)	const	{	return Vector(x - other.x, y - other.y); }	inline Vector operator -(void)					const	{ return Vector(-x, -y); }		friend Vector operator * (float k, const Vector& other) {	return Vector(other.x * k, other.y * k); }			inline float length(void) const { return (float) sqrt(x*x + y*y); }	inline float normalise(void) { float l = length(); if(l > 1.0E-5f) (*this) /= l; return l; }	inline Vector direction(void) const { Vector temp(*this); temp.normalise(); return temp; }	inline float dot_product(const Vector &other)	const	{	return (*this) * other; } // cross product	inline float cross_product(const Vector &other)	const	{	return (*this) ^ other; } // dot product	inline Vector& limit(float length_limit) { float l = length(); if(l > length_limit) (*this) *= (length_limit / l); return (*this); }	Vector& rotate(float angle)	{		float tx = x;		x =  x * cos(angle) - y * sin(angle);		y = tx * sin(angle) + y * cos(angle);		return *this;	}	Vector& transform(const Vector& trans, float rot)	{		Vector D = *this;		D.rotate(rot);		*this = trans + D;		return *this;	}	void randomise(const Vector& min, const Vector& max)	{		x = randf(max.x - min.x) + min.x;		y = randf(max.y - min.y) + min.y;	}};#define ARGB_A(u) (((u)>>24) & 0x000000FF)#define ARGB_R(u) (((u)>>16) & 0x000000FF)#define ARGB_G(u) (((u)>> 8) & 0x000000FF)#define ARGB_B(u) (((u)>> 0) & 0x000000FF)void renderColour(u_int col){	glColor4ub(ARGB_R(col), ARGB_G(col), ARGB_B(col), ARGB_A(col));}void renderCross(float x, float y, float r, int colour){	renderColour(colour);	glBegin(GL_LINES);	glVertex2f(x - r, y - r);	glVertex2f(x + r, y + r);	glVertex2f(x - r, y + r);	glVertex2f(x + r, y - r);	glEnd();	glEndList();}void renderCircle(float x, float y, float r, int colour){	static GLint displaylist=-1;	if(displaylist < 0)	{		displaylist = glGenLists(1);		glNewList(displaylist, GL_COMPILE);		glBegin(GL_LINE_LOOP);		float da = twopi() / 32;		float a = 0.0f;		for(int i = 0; i <= 32; i ++, a += da)			glVertex2f(cos(a), sin(a));		glEnd();		glEndList();	}	glPushMatrix();	glTranslatef(x, y, 0.0f);	glScalef(r, r, r);	renderColour(colour);	glCallList(displaylist);	glPopMatrix();}struct Asteroid{	Vector position;	Vector velocity;	float mass;	float radius;};void move_asteroid(Asteroid& a, float dt){	a.position += a.velocity * dt;}bool collide_asteroids(Asteroid& a, Asteroid& b){	// distance between asteroids (squared).	Vector delta(a.position - b.position);	float distance_squared = delta.dot_product(delta);	// radius of the asteroids.	float combined_radius = (a.radius + b.radius);	float combined_radius_squared = (combined_radius * combined_radius);	// object distance (squared) great than radius (squared). no collision.	if(combined_radius_squared < distance_squared)		return false;	// what is the direction of the collision	float distance = sqrt(distance_squared);	Vector collision_normal = delta / distance;	// how far the objects intersect	float intersection_depth = (combined_radius - distance);	// compute inverse of masses for both asteroids.	float inverse_mass_a = (a.mass <= 0.0000001f)? 0.0f : 1.0f / a.mass;	float inverse_mass_b = (b.mass <= 0.0000001f)? 0.0f : 1.0f / b.mass;	// separate asteroids so they stop intersecting	a.position += collision_normal * (intersection_depth * inverse_mass_a / (inverse_mass_a + inverse_mass_b));	b.position -= collision_normal * (intersection_depth * inverse_mass_b / (inverse_mass_a + inverse_mass_b));	// how hard the objects impact	Vector combined_velocity = (a.velocity - b.velocity);	float impact_speed = combined_velocity.dot_product(collision_normal);	// object are moving away from each other. ignore collision response.	if(impact_speed > 0.0f) 		return true;	// how much the asteroids should bounce off each other.    	const float collision_elasticity = 0.7f;	// the instantaneous collision impulse.	float collision_impulse_magnitude = -(1.0f + collision_elasticity) * impact_speed / (inverse_mass_a + inverse_mass_b);	Vector collision_impulse = collision_impulse_magnitude * collision_normal;	// the change in momentum to each asteroids (change in velocity from collision).	a.velocity += collision_impulse * inverse_mass_a;	b.velocity -= collision_impulse * inverse_mass_b;	return true;}int width = 1024;int height = 764;Asteroid asteroids[100];int asteroid_count=100;Vector mousepos(0, 0);Vector mousevel(0, 0);bool attract=false;bool repel=false;bool scrolling = true; // screen is relative to the mouse cursor.void update_mouse(){	if(scrolling)	{		POINT point;		GetCursorPos(&point);		mousevel.x = (point.x - width/2);		mousevel.y = (point.y - height/2);		SetCursorPos(width/2, height/2);		mousepos.x += mousevel.x;		mousepos.y += mousevel.y;	}}void init(){	for(int i = 0; i < asteroid_count; i ++)	{		asteroids.position.randomise(Vector(0, 0), Vector(width, height));		asteroids.velocity.randomise(Vector(-width, -height), Vector(width, height));		asteroids.velocity.limit(50.0f);		asteroids.radius = randf(10.0f, 30.0f);		asteroids.mass = (asteroids.radius * asteroids.radius);	}}void update(float dt){	int passes = 4;	// update velocity.	for(int i = 0; i < asteroid_count; i ++)	{		// move towards mouse position.		Vector delta = (mousepos - asteroids.position);		delta *= (attract)? 1.0f : (repel)? -1.0f : 0.0f;		delta.limit(200.0f);		asteroids.velocity += delta * 0.1f;		asteroids.velocity *= 0.995f;		asteroids.velocity.limit(200.0f);	}	for(int i = 0; i < asteroid_count; i ++)	{		move_asteroid(asteroids, dt);	}	for(int i = 0; i < asteroid_count; i ++)	{		for(int j = i+1; j < asteroid_count; j ++)		{			collide_asteroids(asteroids, asteroids[j]);		}	}	Vector origin = (scrolling)? mousepos : Vector(0, 0);	for(int i = 0; i < asteroid_count; i ++)	{		float maxx = origin.x + width  / 2 + asteroids.radius;		float maxy = origin.y + height / 2 + asteroids.radius;		float minx = origin.x - width  / 2 - asteroids.radius;		float miny = origin.y - height / 2 - asteroids.radius;		if(asteroids.position.x < minx) asteroids.position.x += (maxx - minx);		if(asteroids.position.y < miny) asteroids.position.y += (maxy - miny);		if(asteroids.position.x > maxx) asteroids.position.x -= (maxx - minx);		if(asteroids.position.y > maxy) asteroids.position.y -= (maxy - miny);	}}void render(){	Vector origin = (scrolling)? mousepos : Vector(0, 0);	glMatrixMode(GL_MODELVIEW);	glPushMatrix();	glTranslatef(-origin.x, -origin.y, 0.0f);	renderCross(mousepos.x, mousepos.y, 16.0f, 0xffffffff);	for(int i = 0; i < asteroid_count; i ++)	{		renderCircle(asteroids.position.x, asteroids.position.y, asteroids.radius, 0xffffffff);	}	glPopMatrix();}const char* windowname = "2D sphere collision";void glutDisplay(){	//--------------------------------------------------------------------------	// render stuff	//--------------------------------------------------------------------------	glClearColor(0.2f, 0.2f, 0.2f, 0.0f);	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	glMatrixMode(GL_PROJECTION);	glLoadIdentity();	gluOrtho2D(-width/2.0f, width/2.0f, height/2.0f, -height/2.0f);	glMatrixMode(GL_MODELVIEW);	glLoadIdentity();	HWND focus = GetFocus();	HWND myWindow = FindWindow("GLUT", windowname);	if(focus == myWindow)	{		update_mouse();		update(1.0f / 30.0f);	}	render();	glutSwapBuffers();}void glutTimer(int t){	glutDisplay();	glutTimerFunc(t, glutTimer, (int) (1000.0f / 30.0f));}void glutKeyboard(unsigned char key, int x, int y){	if (key == 27)		exit(0);	if (key == ' ')		init();}void glutMotion(int x, int y){	if(!scrolling)	{		Vector newmousepos(x - width / 2, y - height / 2);		mousevel = newmousepos - mousepos;		mousepos = newmousepos;	}}void glutPassiveMotion(int x, int y){	if(!scrolling)	{		Vector newmousepos(x - width / 2, y - height / 2);		mousevel = newmousepos - mousepos;		mousepos = newmousepos;	}}void glutMouse(int buttons, int state, int x, int y){	if(!scrolling)	{		Vector newmousepos(x - width / 2, y - height / 2);		mousevel = newmousepos - mousepos;		mousepos = newmousepos;	}	if (buttons == GLUT_LEFT_BUTTON)	{		attract = (state == GLUT_DOWN);	}	if (buttons == GLUT_RIGHT_BUTTON)	{		repel = (state == GLUT_DOWN);	}}void glutReshape(int w, int h){	width  = w;	height = h;	glViewport(0, 0, w, h);}void main(int argc, char** argv){	//--------------------------------------------------------------------------	// OpenGL / GLUT init	//--------------------------------------------------------------------------    glutInit( &argc, argv );	glutInitDisplayMode		(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);	glutInitWindowSize		(width, height);	glutInitWindowPosition	(0, 0);	glutCreateWindow		(windowname);		glutKeyboardFunc		(glutKeyboard);	glutMouseFunc			(glutMouse);	glutMotionFunc			(glutMotion);	glutPassiveMotionFunc	(glutPassiveMotion);	glutDisplayFunc			(glutDisplay);	glutReshapeFunc			(glutReshape);	glutTimerFunc			(0, glutTimer, (int) (1000.0f / 60.0f));	glutSetCursor			(0);		init();	glutMainLoop();}