Magic Cube

  static final int TEXTURE_HEIGHT = 256;

///////////////////////////////////////////////////////////////////////////////////////////////////

  private float computeAngle(float dx, float dy)

    {

    float PI = (float)Math.PI;

    double angle = Math.atan2(dy,dx);

    float ret = (float)(3*PI/2-angle);

    if( ret>2*PI ) ret-= 2*PI;

    return ret;

    }

///////////////////////////////////////////////////////////////////////////////////////////////////

  private void drawCurrVertex(Canvas canvas, Paint paint, float left, float r, float stroke, float pX,float pY, float cX, float cY, float nX, float nY)

    {

    pX = (0.5f+pX)*TEXTURE_HEIGHT;

    pY = (0.5f-pY)*TEXTURE_HEIGHT;

    cX = (0.5f+cX)*TEXTURE_HEIGHT;

    cY = (0.5f-cY)*TEXTURE_HEIGHT;

    nX = (0.5f+nX)*TEXTURE_HEIGHT;

    nY = (0.5f-nY)*TEXTURE_HEIGHT;

    canvas.drawLine(left+pX,pY,left+cX,cY,paint);

    float aX = pX-cX;

    float aY = pY-cY;

    float bX = cX-nX;

    float bY = cY-nY;

    float aLen = (float)Math.sqrt(aX*aX+aY*aY);

    float bLen = (float)Math.sqrt(bX*bX+bY*bY);

    aX /= aLen;

    aY /= aLen;

    bX /= bLen;

    bY /= bLen;

    float sX = (aX-bX)/2;

    float sY = (aY-bY)/2;

    float sLen = (float)Math.sqrt(sX*sX+sY*sY);

    sX /= sLen;

    sY /= sLen;

    float startAngle = computeAngle(bX,-bY);

    float endAngle   = computeAngle(aX,-aY);

    float sweepAngle = endAngle-startAngle;

    if( sweepAngle<0 ) sweepAngle += 2*Math.PI;

    float R = r*TEXTURE_HEIGHT+stroke/2;

    float A = (float)(R/(Math.cos(sweepAngle/2)));

    float rX = cX + A*sX;

    float rY = cY + A*sY;

    startAngle *= 180/(Math.PI);

    sweepAngle *= 180/(Math.PI);

    canvas.drawArc( left+rX-R, rY-R, left+rX+R, rY+R, startAngle, sweepAngle, false, paint);

    }

///////////////////////////////////////////////////////////////////////////////////////////////////

  void drawRoundedPolygon(Canvas canvas, Paint paint, int left, float[] vertices, float stroke, int color, float r)

    {

    stroke *= TEXTURE_HEIGHT;

    paint.setAntiAlias(true);

    paint.setStrokeWidth(stroke);

    paint.setColor(color);

    paint.setStyle(Paint.Style.FILL);

    canvas.drawRect(left,0,left+TEXTURE_HEIGHT,TEXTURE_HEIGHT,paint);

    paint.setColor(COLOR_BLACK);

    paint.setStyle(Paint.Style.STROKE);

    int length = vertices.length;

    int numVertices = length/2;

    float prevX = vertices[length-2];

    float prevY = vertices[length-1];

    float currX = vertices[0];

    float currY = vertices[1];

    float nextX = vertices[2];

    float nextY = vertices[3];

    for(int vert=0; vert<numVertices; vert++)

      {

      drawCurrVertex(canvas, paint, left, r, stroke, prevX,prevY,currX,currY,nextX,nextY);

      prevX = currX;

      prevY = currY;

      currX = nextX;

      currY = nextY;

      if( 2*(vert+2)+1 < length )

        {

        nextX = vertices[2*(vert+2)  ];

        nextY = vertices[2*(vert+2)+1];

        }

      else

        {

        nextX = vertices[0];

        nextY = vertices[1];

        }

      }

    }