graphics: CONTOUR-PARAMETERS


BISECTION-ITERATIONS

  The maximum number of bisections that is allowed to find a coarse
  starting point for a new contour between 2 grid points.

  Small values are recommended since a Newton search anyhow refines
  the starting point.

  [Default: 10]

EPSILON-GRADIENT

  The epsilon used to compute the gradient.

  For coordinates near 0, this is the absolute sampling size. For
  large coordinates, the parameter is taken relative.

  When the area is very small (e.g. around 10**-3) or when there
  is a lot of structure in the contours, then it is a good idea to
  reduce the value of this parameter to e.g. 10**-4.

  [Default: 10**-3]

EPSILON-TRACING

  The epsilon used to follow a contour perpendicularly to the
  gradient.

  For coordinates near 0, this is the absolute step size. For
  large coordinates, the parameter is taken relative.

  When the area is very small (e.g. around 10**-3) or when the
  contours make sharp bends, then it is a good idea to reduce
  the value of this parameter to e.g. 10**-4.

  [Default: 10**-3]

GRID-TOLERANCE

  Since the contours are piecewise straight, it can be that a
  contour segment does not appear to pass between 2 grid points
  between the exact contour would pass.

  In such cases, the algorithm checks whether the contour passes
  near a grid point within a certain fraction of the grid size,
  set with this option.

  This parameter rarely needs updating. If the parameter is too
  small, then some contours will be drawn twice. Contours are not
  missed due to a poor setting of this parameter.

  [Default: 0.1]

NEWTON-ITERATIONS

  Maximum number of Newton iterations when refining the starting
  point of a contour and when finding the contour back after a
  step perpendicular to the gradient.

  [Default: 10]

STEP-MAXIMUM

  Maximum number of steps in any single contour.

  If this parameter is too small, then the contours will be drawn
  as a series of overlapping pieces.

  [Default: 500]

Keyword index. Formatted on 10/11/98.