Calculates the derivatives Dx and Dy of mhi and then calculates gradient orientation as: orientation(x,y)=arctan(Dy(x,y)/Dx(x,y)) where both Dx(x,y)' and Dy(x,y)' signs are taken into account (as in cvCartToPolar function). After that mask is filled to indicate where the orientation is valid (see delta1 and delta2 description).

public static void cvCalcMotionGradient(
	IntPtr mhi,
	IntPtr mask,
	IntPtr orientation,
	double delta1,
	double delta2,
	int apertureSize
)

Public Shared Sub cvCalcMotionGradient ( _
	mhi As IntPtr, _
	mask As IntPtr, _
	orientation As IntPtr, _
	delta1 As Double, _
	delta2 As Double, _
	apertureSize As Integer _
)

public:
static void cvCalcMotionGradient(
	IntPtr mhi, 
	IntPtr mask, 
	IntPtr orientation, 
	double delta1, 
	double delta2, 
	int apertureSize
)