Before revision: If sufficiently-wide ranges of the two independent variables were to be tested, a normal shmoo plot would show an operating envelope of some shape not unlike Al Capp's Shmoo, but in practice, this might damage the device under test, and finer-grained views are of much more interest, particularly focusing on published component margins (e.g., - 5% Vcc).
After revision: For testing efficiency sometimes only the border of interest (where a certain value changes its state) is backed up with data in the diagrams thus (often reasonably) assuming the areas outside those transition will stay at those URL Examples for thinned out, multi-color Shmoo diagrams, dated 2015If sufficiently-wide ranges of the two independent variables were to be tested, a normal shmoo plot would show an operating envelope of some shape not unlike Al Capp's Shmoo, but in practice, this might damage the device under test, and finer-grained views are of much more interest, particularly focusing on published component margins (e.g., - 5% Vcc).