一个模拟橡皮筋的程序。

#define _CRT_SECURE_NO_WARNINGS
#include <graphics.h>
#include <conio.h>
#include <stdio.h>

#define NODES 20
#define GRAVITY 1
#define ITER 8

struct Vector
{
  float x, y;

  void operator += (Vector v) { x += v.x; y += v.y; }
  void operator -= (Vector v) { x -= v.x; y -= v.y; }
  void operator *= (Vector v) { x *= v.x; y *= v.y; }

  Vector operator + (Vector v) { Vector t; t.x = x + v.x; t.y = y + v.y; return t; }
  Vector operator - (Vector v) { Vector t; t.x = x - v.x; t.y = y - v.y; return t; }
  Vector operator * (Vector v) { Vector t; t.x = x * v.x; t.y = y * v.y; return t; }
};

struct Node
{
  Vector p; // 坐标
  Vector v; // 速度
} node1[NODES], node2[NODES], *p1 = &node1[0], *p2 = &node2[0];

void Init()
{
  Node n = { {320, 240}, {0} };

  for (int i = 0; i < NODES; i++)
  {
    node1[i] = node2[i] = n;
  }
}

void Update(int mx, int my)
{
  p1[0].p.x = (float)mx;
  p1[0].p.y = (float)my;

  p2[0] = p1[0];

  static Vector g = { 0, GRAVITY }; // 重力
  static Vector sa = { 0.01f, 0.01f };
  static Vector sv = { 0.99f, 0.99f };

  Vector a;
  for (int i = 1; i < NODES - 1; i++)
  {
    a = (p1[i - 1].p - p1[i].p) + (p1[i + 1].p - p1[i].p) + g;
    a *= sa;
    p2[i].v = p1[i].v + a;
    p2[i].v *= sv;
    p2[i].p = p1[i].p + p2[i].v;
  }
  a = (p1[NODES - 2].p - p1[NODES - 1].p) + g;
  a *= sa;
  p2[NODES - 1].v = p1[NODES - 1].v + a;
  p2[NODES - 1].v *= sv;
  p2[NODES - 1].p = p1[NODES - 1].p + p2[NODES - 1].v;

  Node* t = p1; p1 = p2; p2 = t;
}

void Render()
{
  moveto((int)p1[0].p.x, (int)p1[0].p.y);
  for (int i = 1; i < NODES; i++)
  {
    lineto((int)p1[i].p.x, (int)p1[i].p.y);
  }
}

void DrawFPS()
{
  static DWORD fps = 0;
  static DWORD t = GetTickCount();
  static TCHAR str[64];

  if (++fps >= 100)
  {
    DWORD tt = GetTickCount();
    _stprintf(str, _T("FPS: %d"), 100 * 1000 / (tt - t));
    t = tt;
    fps = 0;
  }
  outtextxy(0, 0, str);
}

void main()
{
  initgraph(640, 600);
  BeginBatchDraw();
  setlinestyle(PS_SOLID, 3);

  // 设置初始位置和速度
  Init();

  MOUSEMSG m = GetMouseMsg();

  while (!_kbhit() || _getch() != 27) // 按ESC退出
  {
    while (MouseHit()) m = GetMouseMsg();

    for (int i = 0; i < ITER; i++) Update(m.x, m.y);
    cleardevice();
    Render();
    DrawFPS();
    FlushBatchDraw();
    Sleep(10);
  }

  EndBatchDraw();
  closegraph();
}

结果：

模拟橡皮筋_#include