During correlation and optional postprocessing, Vic presents a wide range of output data available for 3D and contour plotting, extraction, and export. This application note gives an overview of commonly presented variables.
Output Variables
Always Present
 X [mm] – metric position along the Xaxis (by default, the horizontal axis).
 Y [mm] – metric position along the Yaxis (by default, the vertical axis).
 Z [mm] – metric position along the Zaxis (by default, the outofplane axis).
 Sigma [pixel] – the 1standard deviation confidence in the match, in pixels. 0 indicates a perfect match; higher numbers indicate a noise, excessive gradients, or possibly a failed match.
 U [mm] – metric displacement along the Xaxis, from the reference image. For the reference image, this value will always be 0.
 V [mm] – metric displacement along the Yaxis.
 W [mm] – metric displacement along the Zaxis.
 x [pixel] – the X location, in the raw image, of the data point,
 y [pixel] – the Y location, in the raw image, of the data point.
 u [pixel] – the raw Xaxis displacement between the reference image and a given image, in pixels. This is an internal variable which feeds into the triangulation algorithm to generate the 3D metric displacement data. Effectively, this variable is the output of a 2D correlation between the reference camera 0 image and the deformed camera 0 image.
 v [pixel] – the raw Yaxis displacement between the reference image and a given image, in pixels.
 q [pixel] – the raw Xaxis disparity between the camera 0 image and camera 1 image, in pixels. This is an internal variable which feeds into the triangulation algorithm to generate the 3D metric shape data. Effectively, this variable is the output of a 2D correlation between the reference camera 0 image and a given camera 1 image.
 r [pixel] – the raw Yaxis disparity between the camera 0 image and camera 1 image, in pixels.
 q_ref [pixel] – this is the same as the computed Xaxis disparity but is reserved for the software and cannot be edited by the user. This variable is used for retriangulation.
 r_ref [pixel] – the reserved Yaxis disparity.
Strain Variables
 exx [1] – strain in the Xdirection. Positive numbers indicate tension; negative numbers indicate compression.
 eyy [1] – strain in the Ydirection.
 exy [1] – shear strain.
 e1 [1] – the major principal strain.
 e2 [1] – the minor principal strain.
 gamma [1] – the principal strain angle, measure counterclockwise from the positive Xaxis.
Velocity Variables
 dU/dt [1] – the rate of change of the Udisplacement; that is, the velocity of a given point in the X direction.
 dV/dt [1] – velocity in the Y direction.
 dW/dt [1] – velocity in the Z direction.
 dExx/dt [1] – the rate of change of strain in X, or strain rate in X.
 dEyy/dt [1] – the strain rate in Y.
 dExy/dt [1] – the shear strain rate.
 Note: principal strain rates are not calculated because principal strains, by nature, do not have a consistent reference frame from one image to the next.
Confidence Margins
 Sigma_X [mm] – the 1standarddeviation (67%) uncertainty in the Xaxis.
 Sigma_Y [mm] – the 1standarddeviation (67%) uncertainty in the Yaxis.
 Sigma_Z [mm] – the 1standarddeviation (67%) uncertainty in the Zaxis.
2DSpecific Variables
 x_c, y_c, u_c, v_c  these variables appear in the extraction dialog. If a scale calibration is present, they represent the scaled position and displacement. If no scale calibration is present, they're equal to the pixel values.
Deformed Variables (export only)
 Xp – the deformed X value, equal to X+U. This is an option in the export dialog and is added for convenience.
 Yp – the deformed Y value, equal to Y+V.
 Zp – the deformed Z value, equal to Z+W.
