Re: [R] Lattice wireframe: How to avoid drawing lines around polygons when using shade=TRUE

From: Deepayan Sarkar <deepayan.sarkar_at_gmail.com>
Date: Wed, 30 Jul 2008 16:40:58 -0700

On Sun, Jul 27, 2008 at 1:41 AM, Oliver M. Haynold <inquiries_at_haynold.com> wrote:

> On Sun, 27 Jul 2008 05:00:48 +0000, Oliver M. Haynold wrote:
>> I am using wireframe from the lattice package, with the shade option set
>> to TRUE. When I output to PDF or Postscript, a line gets drawn around
>> each polygon of my surface which causes ugly Moiré effects and doesn't
>> make sense in my application (think the plot of Maunga Whau--gridlines
>> don't make sense). This does not happen when I display on the screen--
>> then I just get the surface as intended.
>
> I have done some research on the problem. On inspection of the PDF file
> generated by lattice, it turns out that it does not actually contain any
> instructions to draw lines between the triangles of the surface plot.
> Yet, Evince and Acrobat Reader both show these lines, with disagreeable
> consequences for printing and screen display.

Does the rendering improve if you unset the "smooth line art" option in Acrobat's settings?

> Ghostscript, however, does
> not and renders the surface as a solid block, as it should be. Thus, a
> workaround for the problem is to put the file generated by lattice
> through Ghostscript and to convert it into a high-resolution image file.
>
> The most likely reason for the problem I can think of is that the
> triangles generated by lattice don't overlap but just border each other.
> This might cause some renderers to leave a little space between them. If
> this explanation is correct, a solution would be to have lattice, or
> specifically wireframePanelCalculations, plot the triangles with a tiny
> bit of overlap.

I don't think that's going to happen.

-Deepayan



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