Table Of Contents
Stereo Correspondence (Block Matching) (G Dataflow)
Computes the disparity map for a pair of stereo images using a block matching method.
This node implements the entire 3D reconstruction process internally until the disparity information is available. The node internally rectifies the left and right images and then use the rectified images to compute the disparity information.
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postfilter options
Disparity information obtained from stereo correspondence and how it is improved.
texture threshold
Minimum sum of absolute value (SAD) at each pixel to be considered to be a valid disparity.
uniqueness ratio
Input that specifies how unique the match at each pixel should be to considered as valid.
speckle window size
Maximum allowed deviation in neighboring pixels disparity values.
The speckle window size defines the following interval: [current disparity - (speckle window size x scaling factor), current disparity + (speckle window size x scaling factor)], where the scaling factor equals 16. For example, if the current disparity is 128 and the speckle window size is 5, then the speckle window size defines an interval [48, 208].
speckle range
Number of neighboring pixel disparities the speckle filter must locate before a given pixel disparity is considered valid.
A pixel disparity is valid if the value falls within the interval defined in speckle window size.
prefilter options
Options that specify how the image is conditioned before stereo correspondence is performed.
filter type
Type of filtering operation that is applied to the input images.
filter size
Size of the filter.
The value must be odd.
filter cap
Input that specifies the filter cap.
binocular stereo session in
Reference to the binocular stereo vision session on which this node operates.
left image in
Reference to the input image from the left camera in the binocular stereo system.
right image in
Reference to the input image from the right camera in the binocular stereo system.
disparity image in
Reference to the image that will contain the disparity information after the node executes.
score image in
Reference to the image that will contain the score information associated with the disparity image after the node executes.
error in
Error conditions that occur before this node runs.
The node responds to this input according to standard error behavior.
Standard Error Behavior
Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.
Default: No error
correspondence options
Options that specify how the block matching algorithm will work for computing the disparity information using stereo correspondence.
method
Metric used to compute matches between the left and right images.
Only the sum of absolute differences (SAD) is supported.
window size
Size of the window that is used to compute the matching score at each pixel in the image.
minimum disparity
Minimum distance between the same point in the left and right rectified images.
number of disparities
Maximum distance between the same point in the left and right rectified images.
You can use the Get Maximum Disparity node to compute this value if you know the minimum depth of the object under inspection from the camera.
max left right disparity change
Maximum allowed difference in the disparity value of a pixel with the disparity values of pixels immediately to its left and right.
If the difference in disparity is greater than this value, then the pixel is set to have an invalid disparity.
subpixel
Option that computes the disparities with subpixel accuracy when enabled.
Bilinear interpolation is used to compute disparities with subpixel accuracy.
invalid disparity replace value
Pixel value assigned to invalid disparity values in the output disparity image.
Use the same value that is used with the Stereo Correspondence (Block Matching) node or the Stereo Correspondence (SG Block Matching) node.
process band
Boolean that determines how to compute the disparity.
| True | minimum disparity and number of disparities values are ignored and the node processes the entire image to compute the disparity. |
| False | The overlap area is replaced with the invalid pixel value. |
Depending on the overlap between the left image and the right image, the interpolated disparities in the overlap area may not be correct.
Default: False
binocular stereo session out
Reference to the stereo vision session on which this node operates.
disparity image out
Reference to the output image that contains the computed disparity values.
score image out
Reference to the output image that contains the scores associated with disparity values returned in disparity image out.
Each pixel in the image contains a value between 0 and 1000. A value of 1000 indicates full confidence in the computed disparity value at that pixel coordinates. A value of 0 indicates no confidence in the computed disparity value.
error out
Error information.
The node produces this output according to standard error behavior.
Standard Error Behavior
Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.
Where This Node Can Run:
Desktop OS: Windows
FPGA: Not supported
Web Server: Not supported in VIs that run in a web application