Tensor HeightField::operator()(math::Vector2f const & p) const
{
static const int dx = 2, dy = 2;
if (m_image.isNull())
{
return Tensor();
}
QPoint ip = m_image.toImageCoords(p).toPoint();
if (! QRect(QPoint(0,0), m_image.size()-QSize(dx,dy)).contains(ip))
{
return Tensor();
}
QRgb pix0 = m_image.pixel(ip);
float f0 = QColor::fromRgb(pix0).valueF();
QRgb pix1 = m_image.pixel(ip + QPoint(dx,0));
float f1 = QColor::fromRgb(pix1).valueF();
QRgb pix2 = m_image.pixel(ip + QPoint(0,dy));
float f2 = QColor::fromRgb(pix2).valueF();
qreal dHx = 100.0f * (f1 - f0);
qreal dHy = 100.0f * (f2 - f0);
qreal f = atan2f(dHy, dHx) + M_PI/2.0f;
qreal r = sqrtf(pow2(dHx) + pow2(dHy));
return Tensor(r, f);
}
math::Tensor BasisField::operator()(math::Vector2f const & p) const
{
if (0 == m_singularityType)
{
return scale * m_regularValue;
}
else
{
Q_ASSERT(m_singularityType < NumSingularityTypes);
Vector2f v = (p - p0).normalized();
float x = v(0);
float y = v(1);
switch (m_singularityType)
{
case SingularityType_Center:
return scale * math::Tensor::fromValues(pow2(y)-pow2(x), -2.0f*x*y);
case SingularityType_Wedge:
return scale * math::Tensor::fromValues(x, y);
case SingularityType_Node:
return scale * math::Tensor::fromValues(pow2(x)-pow2(y), 2.0f*x*y);
case SingularityType_Trisector:
return scale * math::Tensor::fromValues(x, -y);
case SingularityType_Saddle:
return scale * math::Tensor::fromValues(pow2(x)-pow2(y), -2.0f*x*y);
case SingularityType_Focus:
return scale * math::Tensor::fromValues(pow2(y)-pow2(x), 2.0f*x*y);
default:
// not reached, hopefully
return math::Tensor();
}
}
}