# Lineout Computation

Here we describe the numerical interpolation used in performing lineouts.

Lineouts can be performed in two basic modes; sampled and non-sampled. In addition, the variable(s) being processed by a lineout operation can be either piecewise-constant (e.g. zone-centered) or piecewise-linear (e.g. node-centered). Also, if a lineout operation is being performed on an *expression* variable, its important to keep in mind that that variable may have undergone re-centering interpolation (e.g. nodes->zones or zones->nodes) before the lineout operation processes it.

## NON-sampled lineouts

In this case, an intersection of the line and the zones (or cells) of the mesh is performed. Search optimizations are used to minimize the amount of computation necessary to find all zones intersecting the line. All zones intersecting the line are taken into account. The zones are then sorted as per their occurance along the line. Then, the