Date: Wed Apr 23 2014 - 09:40:28 MDT
Hi Lesley,
Dave, who would normally answer this question, is out of the office at the moment.
You can read a write-up on the different modes at:
http://www.ncl.ucar.edu/Document/HLUs/Classes/ContourPlot.shtml
Search for the words "Raster fill" and you'll see a discussion on this. It includes a mention of the cell size. The "Cell fill" discussion follows this one.
You can get another description by reading the description of the "cnFillMode" resource:
http://www.ncl.ucar.edu/Document/Graphics/Resources/cn.shtml#cnFillMode
Basically, AreaFill does automatic smoothing of the contours, and can be slower for larger grids.
RasterFill and CellFill are are more "boxy" form of contouring, where colors are assigned to grid cells. The difference is how the colors are drawn, and neither of these two support shading. The RasterFill description says it doesn't support transparency, but this is no longer true, as we added transparency support in NCL V6.2.0.
CellFill has a resource that allows you to outline the grid cells.
Sometimes it's hard to tell the difference between raster fill and area fill if you have a high resolution grid and have potentially turned on raster smoothing. But, you may notice that raster fill can be *much* faster in these cases.
You can see some raster fill examples at:
http://www.ncl.ucar.edu/Applications/raster.shtml
For whatever reason, we don't have a page on cell fill. I think this is just not used as much as raster fill. Perhaps Dave can expand on this when he gets back.
I've included a very simple script that you can run as-is, to see a quick difference between the three.
--Mary
On Apr 21, 2014, at 3:23 PM, lsmith@ucar.edu wrote:
> Hi
> I'm wondering what goes on behind the scenes in various Raster modes.
> Does averaging go on? How do you know how many points are averaged over?
>
> What does cnRasterMinCellSizeF do?
> I can change the values of this and it
> doesn't seem to have much (any?) effect on my plot.
>
> What's the difference between cnFillMode = "CellFill" and
> cnFillMode = "RasterFill" ?
> What's the difference between cnFillMode = "CellFill" and "AreaFill"?
> Thanks for any tips,
> -Lesley Smith
>
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- application/octet-stream attachment: contour.ncl
