函数用来生成黑白色的云朵.该函数生成该图的一个象素的灰度值

参数说明:

int x, int y: 云朵图对应的象素位置

int x0,int y0,float FX,float FY,float Ci,float Cj,float T0,float K:用来调整云朵亮度、形状、位置等的参数。初始化一般如下

 Ci = 6.0f;

       FX = 1.0f / 120;

       FY = 1.0f / 240;

      fK = 1.0f;

      T0 = 0.0f;

      Cj = 6.0f;

      x0 = 30;

      y0 = 10;

float CGenerateCloudDoc::GenerateCloud(int x, int y,int x0,int y0,float FX,float FY,float Ci,float Cj,float T0,float K)

{

 float  LX = 0,LY = 0,T = 0,T1 = 0,T2 = 0,FX1 = 0,FY1 = 0;

 for(int i=1; i<5; i++)

 {

        if(i==1)

  {

   FX1 = FX;

   FY1 = FY;

  }

  LX = sqrt(i) * FX1;

  LY = sqrt(i) * FY1;

  Ci = 0.707 * Ci;

  Cj = 0.707 * Cj;

  T1 = T1 + Ci * sin( LX * (x-x0) ) + T0;

  T2 = T2 + Cj * sin( LY * (y-y0) ) + T0;

    }

 T = K*T1*T2;

 return T;

}