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Jordan,
Evidently the reason we see different things is because the result with 
linewidth < 1 is renderer-dependent; ghostview (which I am using) and 
Illustrator handle the same file differently.
To be sure we are agreeing on the phenomenon: Initially, with 
linewidth=1 in the contourf polygon generation, there was no problem 
with the subregion boundaries, but the polygons were a bit too large, so 
that thin line contours did not land exactly on the boundaries. Setting 
linewidth=0.01 fixes that problem, but introduces renderer-dependent 
artifacts at the subregion boundaries.
The real solution, or part of it, may be in the backend (ps at least, 
maybe others): I think that we want to be able to specify a polygon with 
a zero-width boundary, such that it is filled but not stroked. 
Alternatively, it may be that the problem is one of rounding in the 
conversion of floating point vertices to integers in the renderer, in 
which case removing the boundary line entirely won't help at all.
The division of the domain by cntr.c into subregions is controllable by 
a parameter; I can expose that parameter to the python level (this 
weekend, not this minute). Then setting it to a sufficiently large 
value will take care of the grid problem; and maybe it will have no bad 
side-effects. According to the comment in the contouring code, the 
reason for subdividing is that renderers bog down when filling polygons 
with too many vertices. It may be that this is no longer a problem; 
that comment may date from an earlier era.
Eric
Jordan Dawe wrote:
> Yeah, I see artifacts in the eps file you sent me. I'm looking at it in 
> Illustrator CS, and the artifacts show up in Adobe Acrobat 6.0 as well. 
> They also show up when I take the eps and do a 'convert example.eps 
> example.png' on it. The resulting png is attached.
> 
> The artifacts tend to change when I zoom in, so I'm guessing some of it 
> is related to the renderer in Illustrator, but I'm still worried they 
> will show up when they go to press. When the linewidth =1.0, the 
> artifacts don't show up at all, so I know it's possible to get rid of them.
> 
> I'm willing to hunt through and try to fix this problem, but where would 
> it show up? In the PS render code? In the polygon handers? I know a 
> fair bit of python, but I don't know my way around matplotlib very well...
> 
> Also, do you see any problems with me trying to make the cntr.c code 
> output one polygon per simply-connected region? Cause the current 
> "divide the fig up into 48 smaller areas" thing is annoying as hell when 
> you're working with eps. Matlab's renderer does this, why can't this one?
> 
> Jordan
> 
> ------------------------------------------------------------------------
> 

I was wondering, has anyone looked into extending numerix to handle the new 
scipy? All scipy tests now pass on my 32bit system, but there is some 
incompatibility between new scipy and mpl. For example:
from pylab import *
from scipy import *
plot(linspace(-1,1,100))
show()
Darren

>>>>> "Eric" == Eric Firing <ef...@ha...> writes:
 Eric> Jordan, Strange, I did test the change and it worked fine
 Eric> with your example on my system. I will email you the result
 Eric> in a separate message so as not to clog the list. Then you
 Eric> can tell me if you see the problem in that file. Maybe I am
 Eric> misunderstanding something.
Could be a CVS version problem -- make sure you are both working on
the same CVS file(s) and the same test script. Historically,
non-developer CVS tends to lag...
JDH

Jordan,
Strange, I did test the change and it worked fine with your example on 
my system. I will email you the result in a separate message so as not 
to clog the list. Then you can tell me if you see the problem in that 
file. Maybe I am misunderstanding something.
Eric
Jordan Dawe wrote:
> Eric Firing wrote:
> 
>> Jordan,
>>
>> Thanks, now I see the problem and where it is coming from. In 
>> contour.py, near the bottom, in the contourf method, change the 
>> linewidth from 1 to 0.01, so the line reads:
>> col = PolyCollection(nlist, linewidths=(0.01,))
>>
>> I think this will be OK; based on the comment below the line, I think 
>> I found that using a linewidth of zero was problematic, so I probably 
>> simply used 1 thinking it was small enough not to matter.
>>
>> I will need to make a corresponding change in the CVS version so that 
>> it will get into the next release. I'll do that this evening.
>>
> Sorry about this, but that patch doesn't seem to work. When I open the 
> eps files generated with this change implimented, I get the artifact 
> problem mentioned in the comment; fine lines at the boundaries of the 
> contouring engine's subdomains. In fact, I get the artifacts at 
> linewidths as large as 0.5.
> 
> Jordan
> 
> 
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Eric Firing wrote:
> Jordan,
>
> Thanks, now I see the problem and where it is coming from. In 
> contour.py, near the bottom, in the contourf method, change the 
> linewidth from 1 to 0.01, so the line reads:
> col = PolyCollection(nlist, linewidths=(0.01,))
>
> I think this will be OK; based on the comment below the line, I think 
> I found that using a linewidth of zero was problematic, so I probably 
> simply used 1 thinking it was small enough not to matter.
>
> I will need to make a corresponding change in the CVS version so that 
> it will get into the next release. I'll do that this evening.
>
Sorry about this, but that patch doesn't seem to work. When I open the 
eps files generated with this change implimented, I get the artifact 
problem mentioned in the comment; fine lines at the boundaries of the 
contouring engine's subdomains. In fact, I get the artifacts at 
linewidths as large as 0.5.
Jordan