The "interpolateboundary" tag controls how interpolation boundary face edges are interpolated. This tag has one optional integer argument and zero floating-point arguments. If the integer argument is not specified it is assumed to have a value of 1. A value of 0 specifies that no boundary interpolation behavior should occur (the default behavior when this tag is not specified). A value of 1 indicates that all the boundary edge-chains are sharp creases and that boundary vertices with exactly two incident edges are sharp corners. A value of 2 indicates that all the boundary edge-chains are sharp creases; boundary vertices are not affected.
The "RenderMan" default is 0, however, bridge products override this to be 1. This RenderMan default may be changed in the future.
Since Katana follows the RenderMan defaults, it is the sole bridge product to specify 0.