Upload (indev)

main.cpp

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+#include <graphics.h>
+#include "simulate.h"
+#include "render.h"
+
+int main()
+{
+	Position2D pa, pb, pc;
+	initView();
+	unsigned int days = 0;
+	for(; is_run(); delay_fps(120))
+	{
+		simulate_ex(pa, pb, pc);
+		render(pa, pb, pc);
+		xyprintf(1,1, "A(%.1f,%.1f)  B(%.1f,%.1f)  C(%.1f,%.1f)   [fps %d, day %d]",
+			 x1, y1, x2, y2, x3, y3, (int)getfps(), days);
+		days++;
+
+	}
+	closegraph();
+	return 0;
+}

render.h

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+#include <graphics.h>
+#define NO_OLDNAMES
+#include <math.h>
+
+inline double max(double a,double b) { return a>b?a:b; }
+
+void render(
+	const Position2D& a,
+	const Position2D& b,
+	const Position2D& c
+) {
+	float radix = 1.0;
+
+	cleardevice();
+
+	setcolor(0xff0000);
+	circle(500 + a.x / radix, 400 + a.y / radix, 7);
+	setcolor(0x00ff00);
+	circle(500 + b.x / radix, 400 + b.y / radix, 5);
+	setcolor(0x0000ff);
+	circle(500 + c.x / radix, 400 + c.y / radix, 2);
+}
+
+void initView()
+{
+	initgraph(1000, 800);
+	setcaption("Three-body Simulator - GCC 4.9.2 64bit");
+	setbkcolor(0xFFFFFF);
+}

simulate.h

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+struct Position2D
+{
+	float x;
+	float y;
+};
+
+float G = 1.0f;
+
+float m1 = 15.0f;	// Mass
+float m2 = 10.0f;
+float m3 = 4.0f;
+
+float x1 = 300.0f;
+float y1 = 50.0f;
+float x2 = -100.0f;
+float y2 = -200.0f;
+float x3 = -100.0f;
+float y3 = 150.0f;
+
+float v1_x = 0.0f;
+float v1_y = 0.0f;
+float v2_x = 0.0f;
+float v2_y = 0.0f;
+float v3_x = 0.0f;
+float v3_y = 0.0f;
+
+float t = 0.1;
+
+float qsqrt_nt( float number )
+{
+	float val = number;//初始值
+	float last;
+	do
+	{
+		last = val;
+		val = (val + number / val) / 2;
+	}while(-1e-4 < val - last && val - last < 1e-4);
+	return val;
+}
+
+float sqrt_c( float number )
+{
+	int i;
+	float x2, y;
+	const float threehalfs = 1.5F;
+
+	x2 = number * 0.5F;
+	y  = number;
+	i  = * ( int * ) &y;     
+	i  = 0x5f375a86 - ( i >> 1 ); 
+	y  = * ( float * ) &i;
+	y  = y * ( threehalfs - ( x2 * y * y ) ); 
+	return number*y;
+}
+
+float qsqrt(float number)
+{
+	if(number > 2.0)
+		return sqrt_c(number);
+	else
+		return qsqrt_nt(number); 
+}
+inline float sqr(float number)
+{
+	return number * number;
+}
+
+void simulate(Position2D& a, Position2D& b, Position2D& c)
+{
+	// 计算两两之间的距离 
+	float distance12 = qsqrt(sqr(x1-x2) + sqr(y1-y2));
+    float distance13 = qsqrt(sqr(x1-x3) + sqr(y1-y3));
+    float distance23 = qsqrt(sqr(x2-x3) + sqr(y2-y3));
+
+    if(distance12 <= 5) distance12 = 7;
+    if(distance13 <= 5) distance13 = 7;
+    if(distance23 <= 5) distance23 = 7;
+
+    // 计算一号球
+	float a1_2 = G*m2/sqr(distance12);  // 物体2对物体1的加速度（用上万有引力公式）
+    float a1_3 = G*m3/sqr(distance13);  // 物体3对物体1的加速度
+    float a1_x = a1_2*(x2-x1)/distance12 + a1_3*(x3-x1)/distance13;  // 物体1受到的水平加速度
+    float a1_y = a1_2*(y2-y1)/distance12 + a1_3*(y3-y1)/distance13;  // 物体1受到的垂直加速度
+    v1_x = v1_x + a1_x*t;  // 物体1的速度
+    v1_y = v1_y + a1_y*t;  // 物体1的速度
+    x1 = x1 + v1_x*t;  // 物体1的水平位置
+    y1 = y1 + v1_y*t;  // 物体1的垂直位置 
+    // 写回
+	a.x = x1;
+	a.y = y1;
+
+	// 计算二号球
+	float a2_1 = G*m1/sqr(distance12);
+    float a2_3 = G*m3/sqr(distance23);
+    float a2_x = a2_1*(x1-x2)/distance12 + a2_3*(x3-x2)/distance23;
+    float a2_y = a2_1*(y1-y2)/distance12 + a2_3*(y3-y2)/distance23;
+    v2_x = v2_x + a2_x*t;
+    v2_y = v2_y + a2_y*t;
+    x2 = x2 + v2_x*t;
+    y2 = y2 + v2_y*t ;
+    b.x = x2;
+	b.y = y2;
+
+	// 计算三号球
+	float a3_1 = G*m1/sqr(distance13);
+    float a3_2 = G*m2/sqr(distance23);
+    float a3_x = a3_1*(x1-x3)/distance13 + a3_2*(x2-x3)/distance23;
+    float a3_y = a3_1*(y1-y3)/distance13 + a3_2*(y2-y3)/distance23;
+    v3_x = v3_x + a3_x*t;
+    v3_y = v3_y + a3_y*t;
+    x3 = x3 + v3_x*t;
+    y3 = y3 + v3_y*t;
+    c.x = x3;
+	c.y = y3;
+
+	// 结束 
+
+}
+
+void simulate_ex(Position2D& a, Position2D& b, Position2D& c)
+{
+	for(unsigned int i = 0; i < 10; ++i)
+	{
+		simulate(a, b, c);
+	}
+}