/**
* User barycentric interpolation to determine the shift at a given point.
*/
Vec2d _interpolateShift(const Coordinate& p)
{
Vec2d result;
// calculate the grid cell that this point falls in.
int r = (p.y - _e.getMinY()) / _gridSpacing;
int c = (p.x - _e.getMinX()) / _gridSpacing;
double dx = p.x - (_e.getMinX() + c * _gridSpacing);
double dy = p.y - (_e.getMinY() + r * _gridSpacing);
////
// Using barycentric interpolation.
////
// if we're right on a point (most interestingly if we're right on the upper right point which
// would cause the following two blocks to fail).
if (dx == 0.0 && dy == 0.0)
{
result.val[0] = _getX(r, c);
result.val[1] = _getY(r, c);
}
// if we're in the lower right triangle
else if (dx > dy)
{
Coordinate t1 = gridCoordinate(r, c);
Coordinate t2 = gridCoordinate(r, c + 1);
Coordinate t3 = gridCoordinate(r + 1, c + 1);
double a1 = triArea2(t3, t2, p);
double a2 = triArea2(t1, t3, p);
double a3 = triArea2(t1, t2, p);
double areaSum = a1 + a2 + a3;
result.val[0] = (_getX(r, c) * a1 + _getX(r, c + 1) * a2 + _getX(r + 1, c + 1) * a3) /
areaSum;
result.val[1] = (_getY(r, c) * a1 + _getY(r, c + 1) * a2 + _getY(r + 1, c + 1) * a3) /
areaSum;
}
// if we're in the upper left triangle
else
{
Coordinate t1 = gridCoordinate(r, c);
Coordinate t4 = gridCoordinate(r + 1, c);
Coordinate t3 = gridCoordinate(r + 1, c + 1);
double a1 = triArea2(t3, t4, p);
double a3 = triArea2(t1, t4, p);
double a4 = triArea2(t1, t3, p);
double areaSum = a1 + a3 + a4;
result.val[0] = (_getX(r, c) * a1 + _getX(r + 1, c) * a4 + _getX(r + 1, c + 1) * a3) /
areaSum;
result.val[1] = (_getY(r, c) * a1 + _getY(r + 1, c) * a4 + _getY(r + 1, c + 1) * a3) /
areaSum;
}
return result;
}
/*
* call-seq:
* inspect -> String
*
* Human-readable description.
* ===Return value
* String
*/
VALUE _inspect(VALUE self)
{
VALUE array[6];
array[0]=rb_str_new2("#<%s:(%d, %d, %d, %d)>");
array[1]=rb_class_of(self);
array[2]=_getX(self);
array[3]=_getY(self);
array[4]=_getWidth(self);
array[5]=_getHeight(self);
return rb_f_sprintf(6,array);
}
