[vtk-developers] vtkColorTransferFunction ambiguities about ranges

[David Doria]

On Wed, Apr 24, 2013 at 2:52 PM, Sean McBride <sean at rogue-research.com> wrote:
> Hi all,
>
> I'm debugging another undefined behaviour found by clang (converting large doubles into uint8, again with colour conversions).
>
> I'm finding the docs for vtkColorTransferFunction are not detailed enough.  Specifically:
>
>   // Description:
>   // Add/Remove a point to/from the function defined in RGB or HSV
>   // Return the index of the point (0 based), or -1 on error.
>   // See the description of class vtkPiecewiseFunction for an explanation of
>   // midpoint and sharpness.
>   int AddRGBPoint( double x, double r, double g, double b );
>   int AddRGBPoint( double x, double r, double g, double b,
>                    double midpoint, double sharpness );
>   int AddHSVPoint( double x, double h, double s, double v );
>   int AddHSVPoint( double x, double h, double s, double v,
>                    double midpoint, double sharpness );
>
> What is the allowable/required/expected range of these things?  Should RGB values always be 0 to 1?  Likewise for HSV?  Is hue 0 to 1?  0 to 2π?  0 to 360?  etc.  Am I just missing where this is documented?
>
> Cheers,

I'm not sure if vtkColorTransferFunction is consistent, but I added
the ranges for color space conversions to the vtkMath documentation a
while back, e.g.

http://www.vtk.org/doc/nightly/html/classvtkMath.html#acda272197c6723e3ff6e72822b1e1d79

David