Optimize Settings for Performance/Quality

This topic provides an overview of the parameters affecting performance and quality of the stereo camera point cloud.

General Settings

Parameter	Performance Setting	Opposite setting
Threads	Set the number of threads as high as possible, but not higher than the number of actual CPU cores. This should already be the default setting, but you might verify if NxLibs autodetection methods for the CPU architecture set this value correctly.	None
CUDA	With many graphics cards using CUDA to perform computations on the GPU will speed up stereo matching and other operations.	Disable CUDA when your PC has no CUDA compatible GPU, or a GPU with very poor performance. NxLib will use the CPU-based implementations instead.

Capture Parameters

Parameter	Performance Setting	Opposite setting
FlexView	Operate the camera in one-shot mode by disabling multi pattern acquisition (i.e. set the FlexView node to false )	Setting the FlexView node to a number of 2 or higher will acquire multiple image pairs with shifted patterns, leading to higher X, Y and Z resolution (only available on N35 cameras).
Exposure (also see Exposure Limitations)	Setting lower exposures will improve the frame rate when the selected exposure/frame rate exceeds the allowable LED duty cycle. You might compensate for the lower exposure by using analog Gain or GainBoost.	Long exposures will cause wait times in software triggered mode to ensure that the LED duty cycle is not exceeded by the projector flash time. This ensures that the LED will be switched on for the entire image exposure time. The wait times are especially noticeable when using FlexView.
PixelClock	Higher values result in shorter image transfer times.	Lower values require less bus bandwidth and lead to more stable image transfers (eliminating transfer errors).
InitialTrigger	When running the camera untriggered, the frame rate might increase when doing a software trigger for the next image after an image has been captured. This can be achieved by setting InitialTrigger to “Untriggered” and FinalTrigger to “All”. Please refer to the definition of the capture phases.	By default, each Capture command triggers the acquisition of a fresh image.
FinalTrigger
AutoExposure	Disabling automatic exposure and gain adjustment might save a few (≤5) milliseconds that are used for calculating the image mean and reconfiguring the sensor (bus communication time).
AutoGain
UseDisparityMapAreaOfInterest	Setting this parameter to true will reduce the image transfer time by only retrieving the minimal rectangular areas of each sensor necessary for the current stereo matching settings.
DownloadImages	XR series only If you don’t need the images, you can use these parameters to avoid downloading them from the camera
ImageDownloadLimit

Stereo Matching Parameters

Parameter		Performance Setting	Opposite setting
Method		In general the PatchMatch medthod will result in better runtime performance compared to the Sgm* and Correlation methods, especially when the necessary measurement depth range is large.	PatchMatch will generate very high quality disparity maps, but for high FlexView image count the “Correlation” method might deliver slightly more details and increase the effective XY resultion and subpixel depth precision.
Method (when using PatchMatch)		Reduce the number of iterations. Disable tilted matching, coupled propagation and right view validation.	Increase the number of iterations. Enable tilted matching, coupled propagation and right view validation.
Method (when using Sgm* and Correlation)		Setting “SgmAligned” or “SgmDiagonal” for the global stereo matching optimization only uses 4 instead of 8 optimization paths for stereo matching, resulting in faster runtime of ComputeDisparityMap. Alternatively you can use “Correlation” which might run faster when using FlexView many (> 8) images, especially when using CUDA.	Setting “SgmAlignedAndDiagonal” uses 8 optimization paths and yields better disparity map results. When using FlexView with many images (> 8) we recommend to use the “Correlation” method which will also generate more detailed disparity maps.
NumberOfDisparities (only applies to Method Sgm* and Correlation)		Setting smaller values for NumberOfDisparities reduces the correspondence search range for the stereo matcher. This results in (linearly) faster runtime of ComputeDisparityMap, but also reduces the measurable depth range in z-direction of the camera.	Larger values enlarge the measurement volume.
Filling		Disabling as many post processing steps as possible results in faster runtime of ComputeDisparityMap.	Post processing of the disparity map might enhance the data quality for your specific application.
Speckle Removal
Median Filtering
AreaOfInterest		The stereo matching algorithm can be resticted to run only on a smaller image region. The smaller the specified AOI is, the more computation time will be saved in the ComputeDisparityMap command.
Scaling		With the scaling parameter the resolution of the rectified images and the resulting 3D data can be reduced by an arbitrary scale factor. This can significantly reduce the runtime of ComputeDisparityMap.