BUG #1947: isofill does not handle out of bounds levels correctly.

[danlipsa]

When smallest level is bigger than min scalar value or biggest level
is smaller than max scalar value isofill creates the wrong image.

[danlipsa]

@doutriaux1 @aashish24 Please review. I did not add a new test here because we already had tests for this but they had wrong baselines.
New baselines in:
CDAT/uvcdat-testdata#143

[danlipsa]

@doutriaux1 The confusing part here was that we color by the cell data generated by vtkBandedPolyDataContourFilter. These are the bands from 0 to len(l) - 1. But we can also color by the scalar in the original data - this is point data: this is what you've done in your PR, so that is why you had the fuzzy images. Your PR looked correct, but I did not understand initially how this was working before your change. I forgot about the bands generated by vtkBandedPolyDataContourFilter.

[doutriaux1]

@danlipsa did you also test the last example I posted, I don't think this fixes it.

import cdms2
import vcs

x=vcs.init()
f=cdms2.open("HadSST1870to99.nc")
s=f("sst")
print s.min(),s.max()
iso=x.createisofill()
iso.levels=[-15,-14,-13,-12,-11,-10,-9,-8,-7,-6,35]
x.plot(s,iso)

[danlipsa]

@doutriaux1 I run a selection in ParaView for all cells with scalar >= -6. This selects most cells - note ParaView does not show blanked cells because I save polygonal data which does not support blanking.

This is the image generated by uvcdat - if you look carefully you'll see different colors at the top.

So, I think the image is correct - it looks strange because most values are between -6 and 35.

[danlipsa]

@doutriaux1 Actually, I think you are right, there is something going on here. Some black (the part that is shown blue here) should have been white. See the following image:

[doutriaux1]

@danlipsa yes that is odd. But at least the levels seem to be picked up correctly (on your first plot). I still don't see how it's possible from the code, but it seems to work.

[doutriaux1]

@danlipsa I merged conda_build into your branch (locally) and was able to test it quickly, it seems to work ok. Not sure about the black bit though as you mentioned.

[danlipsa]

@doutriaux1 @aashish24 Please review. This solves all problems I know of.

[doutriaux1]

@danlipsa looks like it's working now. Thanks. But why do we do a pointtocell ?
The reason I'm asking is that I was hoping we could draw isofill/isolines on unstructured grid, even if they did not have vertices information, simply using a point dataset.

[danlipsa]

@doutriaux1 putMaskOnVTKGrid needs to draw black (masked) any cell that has any points hidden. That is why I need pointtocell.

You won't be able to do isolines/isofill for a point dataset. Both need interpolation which only works if you have cells - topology information. Otherwise the algorithm won't know which points to use for interpolation.

[doutriaux1]

@danlipsa I'm attaching a sample zipped nc file, that has coordinate info (lat/lon) but no bounds info (in CF format), vcs cannot plot it, but it should be able to, since we know the point data (lat/lon). It's definitely something for 3.0 anyway, just wanted to ask you about it now before I forget.
add.zip

[doutriaux1]

@danlipsa I updated the baselines, it's good to be merged in as far as I'm concerned. If it's good with you as well, go ahead and merge please.