#### Description:

This attribute specifies the pincushion/barrel distortion coefficient used by a PcdMap. This coefficient is set when the PcdMap is created, but may later be modified. If the attribute is cleared, its default value is zero, which gives no distortion. For pincushion distortion, the value should be positive. For barrel distortion, it should be negative.

Note that the forward transformation of a PcdMap applies the distortion specified by this attribute and the inverse transformation removes this distortion. If the PcdMap is inverted (e.g. using astInvert), then the forward transformation will remove the distortion and the inverse transformation will apply it. The distortion itself will still be given by the same value of Disco.

Note, the value of this attribute may changed only if the PcdMap has no more than one reference. That is, an error is reported if the PcdMap has been cloned, either by including it within another object such as a CmpMap or FrameSet or by calling the astClone function.

Type:

  Double precision.

#### Applicability

##### PcdMap

All PcdMaps have this attribute.
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