水波模仿的实现要领

副标题#e#

在一个波长范畴内，任意点的位移disp=sin(dist)*force+disp_center;

这里设水波为正弦波，振幅为force,disp_center为振中的位移。

推广到任何点，disp=sin(dist%wave_length)*force+disp_center;

这里wave_length为波长。可以看出，在离散的数据中，任何点的位移是有限的荟萃。我们先结构出这个荟萃，在运算进程中，从荟萃中选取一个位移值就行了，而不消及时计较每个点的位移。

措施设计如下：取波长为12，任何点的位移由一个12个元素的数组。

int disp[12];

成立一个数构成存贮各点来振中的间隔

int dist[600][800];

下面生成一个水波

inline void Build_Disp_Matrix()
{
    for(int i = 0; i < 12; ++i)
    disp = static_cast<int>(sin((double)i*30*DXPI/360)*PRECISION);
}
void Create_Ripple(int center_x, int center_y, int force, int damp, int wave_length)
{
    for(int i = 0 ; i < wave_length; ++i)
    {
        disp = force * disp / PRECISION;
    }
    int dist_x, dist_y;
    for(i = 0; i < SCREEN_HEIGHT; ++i)
    {
        for(int j = 0; j< SCREEN_WIDTH; ++j)
        {
            dist_y = i - center_y;
            dist_x = j - center_x;
            dist[j] = static_cast<int>(sqrt(dist_x*dist_x + dist_y*dist_y) + 0.5) % wave_length;
        }
    }
}

#p#副标题#e#

渲染水波的代码与本来的代码一样。

void Render_Ripple(LPDIRECTDRAWSURFACE7 lpdds)
{
    DDSURFACEDESC2 ddsd = { sizeof(ddsd) };
    if(disp_index < 0) disp_index = 12;
    --disp_index;
    lpdds->Lock(NULL,&ddsd, DDLOCK_WAIT | DDLOCK_SURFACEMEMORYPTR, NULL);
    short* lpSrcBuffer = static_cast<short*>(pBmpBack->GetBitmapBuffer());
int pitch = (ddsd.lPitch) >> 1;
    short* lpBuffer = static_cast<short*>(ddsd.lpSurface);
    int left,right,bottom,top;
    int k = 0,l = 0;
    int index_x,index_y;
    int x_off,y_off;
    int pos1,pos2;
    for(int i = 1; i < SCREEN_HEIGHT - 2; ++i)
        for( int j = 1; j < SCREEN_WIDTH - 2; ++j)
        {
            left = right = bottom = top = disp_index;
            left += dist[j -1];
            if(left > 12) left -= 12;
            right += dist[j+1];
            if(right >12) right -= 12;
            bottom += dist[i+1][j];
            if(bottom > 12) bottom -= 12;
            top += dist[i-1][j];
            if(top >12 ) top -= 12;
            x_off = disp[left] - disp[right];
            y_off = disp[top] - disp[bottom];
            index_x = j + x_off;
            index_y = i + y_off;
            pos1 = i*pitch +j;
            pos2 = index_y * 800 + index_x;
if(pos2 < 0 || pos2 > 479999) break;
            lpBuffer[pos1] = lpSrcBuffer[pos2];
        }
    pBmpBack->ReleaseBuffer();
    lpdds->Unlock(NULL);
}