[vtk-developers] Bug in vtkColorTransferFunction

[David Cole]

This was checked in to the VTK-5-0 branch on Dec. 5. Randall, could you 
update and verify that it's fixed...?

Thanks,
David


Randall Hand wrote:

> I've spent the last week beating my head against the wall trying to 
> figure out why my colormap didn't work in my application, but smaller 
> test cases would work.  I finally figured it out just now.  (Filed as 
> bug 2546)
>
> When using a vtkColorTransferFunction, and adding a large number of 
> points (Over 100) in an out-of-order fashion (In my case, I'm reading 
> them from a file and the X's are fairly random, not simply 
> incrementing), it will destroy the colormap.  The problem comes when 
> you add the 100'th point and it tries to resize the colormap.  In this 
> case, it uses a memcpy to copy the colormap into the newly allocated 
> (and large) array.  If that 100th's point is not the highest point in 
> the list, it uses 2 memcpy's, one shifted by one entry to create a 
> "hole" for the newly added entry in the middle.  Unfortunately, it 
> indexes wrong! So the net result:  Blue becomes red, green becomes 
> blue, red becomes the next entry's X, and in general it's just all 
> b0rked.
>
> Attached to the bug ( 
> http://www.vtk.org/Bug/bug.php?op=show&bugid=2546&pos=3 
> <http://www.vtk.org/Bug/bug.php?op=show&bugid=2546&pos=3> ) you'll 
> find a test-case that uses a Mandelbrot fractal source to illustrate 
> the problem. 
>
> -- 
> Randall Hand
> Visualization Scientist,
> ERDC-MSRC Vicksburg, MS
> Homepage: http://www.yeraze.com
>
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