It verifies that all points are on or below all facets. Qhull automatically tests for convexity if it detects precision errors while constructing the hull. Exact arithmetic Delaunay triangulations Imprecise convex hulls How Qhull merges facets Approximating a convex hull Precision problems Since Qhull uses floating point arithmetic, roundoff error occurs with each calculation. This causes problems for most geometric algorithms. Other floating point codes for convex hulls, Delaunay triangulations, and Voronoi diagrams also suffer from these problems.
Measurement error occurs when the input coordinates are from measurements.
Roundoff error occurs when a calculation is rounded to a fixed number of digits, e.g., a floating point calculation. Approximation error occurs when the user wants an approximate result because the exact result contains too much detail. Under imprecision, calculations may return erroneous results. For example, roundoff error can turn a small, positive number into a small, negative number. Qhull does not meet Milenkovic's criterion for accuracy.