exrutils provides tools to process OpenEXR files. For example, you may
want to create a novel sequence for your optical flow algorithm and
compare the estimates against ground truth information. In addition,
your 3D modeller is able to export the depth information to OpenEXR
(usually, this is done by exporting the final rendering to OpenEXR and
additionally storing to Z buffer to the file). As long as you're able to
export the camera position to a csv file or use blender_ole, you can
then use exrflow to compute ground truth optical flow for your sequence.

exrflow
	Please read the following carefully:
	
	Compute "ground truth" optical flow given a set of OpenEXR files
	and the camera position. The positions for each frame a stored
	in a csv file in the format
		a11,a21,a31,a41,a12,a22,...,a44
		a11,a21,a31,a41,a12,a22,...,a44
		.
		.
		.
	where one row corresponds to one frame (or OpenEXR file). The
	aij are the entries of a camera matrix. They can be exported 
	from blender for a single camera with the help of the script
	blender_ole, obtainable from https://github.com/rochus/blender_ole
	
	The OpenEXR files need only provide a Z layer.
	
	The tool assumes a default blender setup, which means using a
	focal length of 35mm and a sensor size of 32mm (note that these
	values are hardcoded in blender up until blender 2.61. Since
	2.61, the user may change these values under the camera options
	pane). This yields a focal length of 2.1875 in a canonical
	camera model:
	
	The opening angle alpha of the blender default camera is
	
	     alpha = atan2(16.0, 35.0) * 2                           (1)
	
	to get the focal length in a canonical camera model, where the image
	plane has an extent of 2.0 (from -1.0 to 1.0) in the largest extent,
	we have to calculate:
	
	     f = b / tan(a/2)                                        (2)
	
	where b = 1.0 (because it is half the image plane width). but as we
	have the 'lens focal length' and the sensor size, we can calculate:
	
	     tan(a/2) = (.5 * sensor size) / lens focal length       (3)
	
	insert (3) into (2) yields
	
	     f = 1.0 / ((.5s) / l)                                   (4)
	
	where s is the sensor size and l the lens focal length.
	Setting s = 32mm and l = 35mm as in the default blender setup yields
	
	     f = 2.1875
	
	If you use an different lens, you can provide the canonical
	focal length with the -f <value> option.
	
	The tool assumes that the camera is looking into the negative Z
	direction using a right-handed coordinate system. Thus, the
	equations to calculate optical flow presented in [1] were
	adapted to reflect this change.
	
	However, if you want to use the default Longuet-Higgins &
	Prazdny equations because your camera does look into the
	positive Z direction (or for whatever reason you have), you can
	switch to these equations with the -l option.

	References:

	[1] The Interpretation of a Moving Retinal Image
	    H. C. Longuet-Higgins and K. Prazdny
	    Proceedings of the Royal Society of London. Series B, Biological
	    Sciences, Vol. 208, No. 1173 (Jul. 17, 1980), pp. 385-397


exrcvview
	This tool shows a sequence of n >= 1 OpenEXR images with the
	help of OpenCV. You may want to transform the images with the -s
	switch to sRGB on the fly.
	If you have a sequence which shall be looped infinitely, pass
	the -l option to exrcvview. Otherwise, exrcvview will stop at
	the last frame and continue showing it.


exr2pgm
	Convert an OpenEXR file to gray-scale PGM.