Re: [Plplot-general] Another conceptional issue using griddata

[Paul W. B. <pa...@pu...>]

Hello,

Thank you for your answer.

> Since your pattern of points is confined to a circular area (and rather
> complete within that area), my suggestion is to try using polar coordinates
> throughout.  Now example 21 obviously uses rectangular coordinates for
> plgriddata, but I presume plgriddata should work just as it is for any
> two-dimensional coordinate system.

Yes, this should work. I will have a look. Not sure if there is the time 
to implement this. Perhaps it is easier to calculate the rays which 
intersect with the eye glass in exactly the points of a rectangular grid.

>  Furthermore, example 16's last page (see
> http://plplot.sourceforge.net/examples-data/demo16/x16.05.png) shows
> plshades can be used with any two-dimensional coordinate system.

Ok, this looks good. This example shows me that it is possible to draw a 
graph of a circle without filling the whole rectangle.

>> Is there a way to use the DTLI algorithm to get a kind of data like in
>> http://m21s26.vlinux.de/math/gsg.png?
> 
> I think yes.  Once you get plgriddata and plshades working for polar
> coordinates it should be a simple matter to use plbox to make a rectangular
> box around the circular area created by plshades.  You can arrange the plbox
> call so the tick marks on the box are for rectangular coordinates
> corresponding to the polar coordinates used for plshades.

Puh... I don't understand this at this moment. I'll have to dive into 
it. Converting it to polar coordinates, ok. This should be no problem. 
Then I would get (I hope so...) a regular grid in polar coordinates. But 
if I convert it back it may not be regular, in x-y, right?
Hm, not sure how to implement this, but it should be possible in any way.

Thank you and regards
Paul.