EasyX—模拟小球自由落体

#include <stdio.h>
#include <graphics.h>

#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
#define R 20
#define T 0.01
#define G 9.8
#define EPSILON 5E-3

int main() {
    initgraph( SCREEN_WIDTH, SCREEN_HEIGHT );
    circle( SCREEN_WIDTH / 2, R, R );

    double h = R;   //小球当前的位置
    double v = 0.0; //初速度

    BeginBatchDraw();

    while( h <= SCREEN_HEIGHT - R ) {
        circle( SCREEN_WIDTH / 2, h, R );   //重新绘制小球
        FlushBatchDraw();

        Sleep( 1 );
        h = h + v * T + 0.5 * G * T * T;
        v = v + G * T;
        if( h > SCREEN_HEIGHT - R ) {
            h = SCREEN_HEIGHT - R;
            v = 0.7 * v;
            v = -v;
        }

        if( abs( v ) < EPSILON && h >= SCREEN_HEIGHT - R ) {
            break;
        }
        cleardevice();
    }
    EndBatchDraw();

    closegraph();
    return 0;
}