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字號： 大大  中中  小小 用C語言畫立體五角星                                    立 體 五 角 星
設(shè)計(jì)思路：
1、通過給定的圓半徑，計(jì)算出圓上平均分布的五個(gè)頂點(diǎn)的坐標(biāo)，再計(jì)算出相應(yīng)小圓的半徑及旋轉(zhuǎn)36度后小圓上平均分布的五個(gè)點(diǎn)的坐標(biāo)。用線將各對應(yīng)點(diǎn)連接起來形成五角星。
2、通過循環(huán)畫間斷弧線形成動(dòng)態(tài)的光芒效果。
3、本例應(yīng)用到數(shù)組及數(shù)學(xué)中的正弦和余弦函數(shù)。
圖例：
 
 
公式：x=x0+r*cos(a);
y=y0-r*sin(a);
a為從起點(diǎn)到該點(diǎn)的旋轉(zhuǎn)角度。
由于C語言中sin、cos等函數(shù)中的參數(shù)是依弧度計(jì)算的，因此需要進(jìn)行度數(shù)轉(zhuǎn)換。一般先用#define PI 
3.1415926這樣的宏定義定義PI。2*PI為一個(gè)圓周，2*PI/360為角度1度的值，簡化為PI/180。比如需要計(jì)算30度的正弦值，按下式：
sin(30*PI/180);
五角星內(nèi)接的小圓半徑的求法： 
  

數(shù)學(xué)公式：yc=r×sin(18°); 或yc=r×cos(72°);
      　　r0=yc÷cos(36°)
 
轉(zhuǎn)成C語言語句：
          yc=r*sin(18*PI/180);
          r0=yc/cos(36*PI/180);
或直接寫成：r0=r*sin(18*PI/180)/cos(36*PI/180);
 
 
例：
#include<graphics.h>
#include<math.h>         /* 插入數(shù)學(xué)頭文件 */
#define PI 3.1415926     /* 宏定義 PI */
float th=PI/180;         /*定義全局變量 th */
main()
{
 int gd=DETECT,gm,i,j;
 initgraph(&gd,&gm,"");
 setbkcolor(BLUE);
 star(320,240,120);   /*調(diào)用自定義函數(shù)star()。*/
 while(!kbhit())       /*下面循環(huán)體是繪制光芒部分，可以不要 */
 {
 setcolor(YELLOW);
 for(j=0;j<20;j++)
 {
    for(i=0;i<120;i++)
    ellipse(320,240,i*3,1+i*3,125+j*20,125+j*10);
    delay(5000);
 }
 setcolor(BLACK);
 for(j=0;j<20;j++)
    {
    for(i=0;i<120;i++)
    ellipse(320,240,i*3,1+i*3,125+j*20,125+j*10);
    delay(5000);
    }
 }
 getch();
 closegraph();
}
 
 star(int x,int y,int r)
 {
     int r0=r*sin(18*th)/cos(36*th); /*計(jì)算小圓半徑r0 */
     int i,color;
     int x1[6],y1[6],x2[6],y2[6];
     for(i=0;i<6;i++)
     {
     x1[i]=x+r*cos((90+i*72)*th); /* 計(jì)算出大圓上的五個(gè)平均分布點(diǎn)的坐標(biāo)*/
     y1[i]=y-r*sin((90+i*72)*th);
     x2[i]=x+r0*cos((54+i*72)*th); /* 計(jì)算出小圓上的五個(gè)平均分布點(diǎn)的坐標(biāo)*/
     y2[i]=y-r0*sin((54+i*72)*th);
     }
     setcolor(RED);
     for(i=0;i<5;i++)           /* 將相應(yīng)的點(diǎn)用線連接起來。*/
     {
     line(x,y,x1[i],y1[i]);
     line(x,y,x2[i],y2[i]);
     line(x1[i],y1[i],x2[i],y2[i]);
     line(x1[i],y1[i],x2[i+1],y2[i+1]);
     }
     for(i=0;i<10;i++)         /* 分別填充相應(yīng)部位，形成立體效果*/
     {
        setfillstyle(1,i%2?RED:LIGHTRED); 
        floodfill(x+10*cos(i*36*th),y-10*sin(i*36*th),RED);
     }
 }
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 shinewave 零點(diǎn)任務(wù) 苗苗 大帥

分享(0) 評論(0) 分類：學(xué)習(xí)44次閱讀　2007-07-06 12:13     
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