[android-developers] google api demo question about drawBitmapMesh algorithm

Hi all,

 

I'm not good at mathematics algorithm, so i can't undanstand the following code

 

private void warp(float cx, float cy) {
            final float K = 10000;  // why it is 10000 ??
            float[] src = mOrig;
            float[] dst = mVerts;
            for (int i = 0; i < COUNT*2; i += 2) {
                float x = src[i+0];
                float y = src[i+1];
                float dx = cx - x;
                float dy = cy - y;
                float dd = dx*dx + dy*dy;
                float d = FloatMath.sqrt(dd);
                float pull = K / (dd + 0.000001f);
               
                pull /= (d + 0.000001f); // so it is pull = d * K / (dd), what is it meaning ?

                

                // let me take a example, there have a triangle, a, b, c

 

                // pull is c/sqrt(a*a + b*b)  then * 10000? what is the result meaning?? maybe the c/sqrt(a*a + b*) is 1 or less 1 or more then 1.  can anyone tell me why  it * 10000?

                // and what it meaning about the result  d * K / (dd), ?

 

                android.util.Log.d("skia", "index " + i + " dist=" + d + " pull=" + pull);

                if (pull >= 1) {
                    dst[i+0] = cx;
                    dst[i+1] = cy;
                } else {
                    dst[i+0] = x + dx * pull;
                    dst[i+1] = y + dy * pull;
                }
            }
        }

 

best regards, thanks.

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