# Maximum Warping Error

As described in the previous section, each pixel in the warped image is generated by sampling the pixel values at the corresponding point in the acquired run-time image. In most cases, the location of a sampling point can be extrapolated from the locations of nearby sampling points. The tool reduces the amount of time and memory required for image warping by extrapolating the locations of some of the sampling points (because the process of mapping a point through a nonlinear transformation is time-consuming).

You can control the amount of extrapolation done by the tool by changing the value of the WarpMaxErrorInPixels property. The tool will extrapolate sampling locations until the difference between the extrapolated and the actual sampling location exceeds the error you specify. Then the tool transforms a pair of points explicitly and resumes extrapolation.

In most cases, you should specify a very small value for this error. The default value for this property is 0.01 pixels. The effect of changing the value of this property on the speed of image warping is very dependent on the degree of radial distortion present in the image. If the image has very little distortion, then changing this property will have little or no effect on warping speed. If the image is heavily distorted, then increasing the value of this property can greatly reduce the amount of time required for warping.

Note: The maximum warping error is not related to the ComputedRMSError property. The computed RMS error, which is measured in uncalibrated space, is a measure that the tool computes to measure how accurately the computed transformation represents the difference between the uncalibrated and raw calibrated vertex points. The maximum warping error is a value that you specify to adjust the accuracy with which the image warping represents the computed transformation.