# 罗朝辉（飘飘白云）

C++博客 :: 首页 :: 新随笔 :: 联系 :: 聚合  :: 管理 ::
 85 随笔 :: 0 文章 :: 169 评论 :: 0 Trackbacks

Android 上实现水波特效二--优化

在上一篇文章《Android 上实现水波特效中对水波波幅的计算是针对每一个像素的，效率比较低，尤其是在手机上运行，相当缓慢。我们可以利用线性插值进行优化，这样可以将计算减少一半（MeshSize 2）或减少四分之三（MeshSize 4），效率得以大大提升，即使是在水机上也能较为流畅地运行。

 static final int MeshSize = 2; static final int MeshShift = 1;   int m_meshWidth; int m_meshHeight; m_meshWidth = m_width / MeshSize + 1; m_meshHeight = m_height / MeshSize + 1;;   void rippleSpread() { m_waveFlag = false;   int i = 0, offset = 0; for (int y = 1; y < m_meshHeight - 1; ++y) { offset = y * m_meshWidth; for (int x = 1; x < m_meshWidth - 1; ++x) { i = offset + x; m_buf2[i] = (short)(((m_buf1[i - 1] + m_buf1[i + 1]                     + m_buf1[i - m_meshWidth]                     + m_buf1[i + m_meshWidth]) >> 1) - m_buf2[i]);               m_buf2[i] -= (m_buf2[i] >> 5);             m_waveFlag |= (m_buf2[i] != 0);        }     }        if (m_waveFlag){        m_waveFlag = false;               for (int y = 1; y < m_meshHeight - 1; ++y) {           offset = y * m_meshWidth;           for (int x = 1; x < m_meshWidth - 1; ++x) {              i = offset + x;              m_bufDiffX[i] = (short)((m_buf2[i + 1] - m_buf2[i - 1]) >> 3);              m_bufDiffY[i] = (short)((m_buf2[i + m_meshWidth] - m_buf2[i - m_meshWidth]) >> 3);                           m_waveFlag |= (m_bufDiffX[i] != 0 || m_bufDiffY[i] != 0);           }        }    }       //交换波能数据缓冲区    short[] temp = m_buf1;     m_buf1 = m_buf2;    m_buf2 = temp; }

 Point p1, p2, p3, p4; Point pRowStart, pRowEnd, p, rowStartInc, rowEndInc, pInc;   void rippleRender() {     int px = 0, py = 0, dx = 0, dy = 0;    int index = 0, offset = 0;       for (int j = 1; j < m_meshHeight; ++j) {       offset = j * m_meshWidth;       for (int i = 1; i < m_meshWidth; ++i) {              index = offset + i;          p1.x = m_bufDiffX[index - m_meshWidth - 1];          p1.y = m_bufDiffY[index - m_meshWidth - 1];          p2.x = m_bufDiffX[index - m_meshWidth];          p2.y = m_bufDiffY[index - m_meshWidth];          p3.x = m_bufDiffX[index - 1];          p3.y = m_bufDiffY[index - 1];          p4.x = m_bufDiffX[index];          p4.y = m_bufDiffY[index];                   pRowStart.x = p1.x << MeshShift;          pRowStart.y = p1.y << MeshShift;          rowStartInc.x = p3.x - p1.x;          rowStartInc.y = p3.y - p1.y;                   pRowEnd.x = p2.x << MeshShift;          pRowEnd.y = p2.y << MeshShift;          rowEndInc.x = p4.x - p2.x;          rowEndInc.y = p4.y - p2.y;            py = (j - 1) << MeshShift;          for (int y = 0; y < MeshSize; ++y) {             p.x = pRowStart.x;             p.y = pRowStart.y;                         // scaled by MeshSize times             pInc.x = (pRowEnd.x - pRowStart.x) >> MeshShift;             pInc.y = (pRowEnd.y - pRowStart.y) >> MeshShift;                         px = (i - 1) << MeshShift;              for (int x = 0; x < MeshSize; ++x) {                 dx = px + p.x >> MeshShift;                 dy = py + p.y >> MeshShift;                                 if ((dx >= 0) && (dy >= 0) && (dx < m_width) && (dy < m_height) ) {                     m_bitmap2[py * m_width + px] = m_bitmap1[dy * m_width + dx];                  }                  else {                     m_bitmap2[py * m_width + px] = m_bitmap1[py * m_width + px];                  }                    p.x += pInc.x;                  p.y += pInc.y;                  ++px;              }                           pRowStart.x += rowStartInc.x;              pRowStart.y += rowStartInc.y;              pRowEnd.x += rowEndInc.x;              pRowEnd.y += rowEndInc.y;              ++py;          }       }    } }

posted on 2010-09-28 11:49 罗朝辉 阅读(1319) 评论(0)  编辑 收藏 引用 所属分类: 计算机图形学移动开发Algorithms