EasyX—模拟小球自由落体

 1 #include <stdio.h>
 2 #include <graphics.h>
 3 
 4 #define SCREEN_WIDTH 640
 5 #define SCREEN_HEIGHT 480
 6 #define R 20
 7 #define T 0.01
 8 #define G 9.8
 9 #define EPSILON 5E-3
10 
11 int main() {
12     initgraph( SCREEN_WIDTH, SCREEN_HEIGHT );
13     circle( SCREEN_WIDTH / 2, R, R );
14 
15     double h = R;   //小球当前的位置
16     double v = 0.0; //初速度
17 
18     BeginBatchDraw();
19 
20     while( h <= SCREEN_HEIGHT - R ) {
21         circle( SCREEN_WIDTH / 2, h, R );   //重新绘制小球
22         FlushBatchDraw();
23 
24         Sleep( 1 );
25         h = h + v * T + 0.5 * G * T * T;
26         v = v + G * T;
27         if( h > SCREEN_HEIGHT - R ) {
28             h = SCREEN_HEIGHT - R;
29             v = 0.7 * v;
30             v = -v;
31         }
32 
33         if( abs( v ) < EPSILON && h >= SCREEN_HEIGHT - R ) {
34             break;
35         }
36         cleardevice();
37     }
38     EndBatchDraw();
39 
40     closegraph();
41     return 0;
42 }