Thread Subject: drawing patch to obscure lines

hi all,

i have some lines drawn on axes using the standard 'plot'
function. now i want to use 'patch' to overlay a
transparent shading _over_ the lines at a certain point such
that it shades (and somewhat obscures) the lines underneath.
 here is what i have tried so far:

figure, plot(rand(10));
verts1 = [1 .5; 10 .5; 10 1; 1 1];
faces1 = [1 2 3 4];
patch('faces',faces1,'vertices',verts1,'edgecolor','none',...
'facecolor',[.65 .65 .65],'facealpha',.25)

while this works to shade the axes, it is not actually
showing up as an overlay of the plotted lines. what i am
expecting here is that the patch will 'dim' the plotted
lines in the range [0.5 : 1]. any hints on how i might be
able to accomplish this?

thanks in advance,
bryan

"Bryan " <cssmwbs@gmail.com> wrote in message
<fvafa9$a2t$1@fred.mathworks.com>...
> hi all,
>
> i have some lines drawn on axes using the standard 'plot'
> function. now i want to use 'patch' to overlay a
> transparent shading _over_ the lines at a certain point such
> that it shades (and somewhat obscures) the lines underneath.
> here is what i have tried so far:
>
> figure, plot(rand(10));
> verts1 = [1 .5; 10 .5; 10 1; 1 1];
> faces1 = [1 2 3 4];
> patch('faces',faces1,'vertices',verts1,'edgecolor','none',...
> 'facecolor',[.65 .65 .65],'facealpha',.25)
>
> while this works to shade the axes, it is not actually
> showing up as an overlay of the plotted lines. what i am
> expecting here is that the patch will 'dim' the plotted
> lines in the range [0.5 : 1]. any hints on how i might be
> able to accomplish this?
>
> thanks in advance,
> bryan

It can't be done by the method you're describing because
using transparency requires the open gl renderer, which
ALWAYS draws lines on top of patches, (which annoys me to no
end) so you can't put a line behind a patch. You might be
able to fake it by drawing a new set of lines just in the
patch area that are a different color (a mix of their
original color and the patch color) but if the data points
don't line up with the edges of your patch that might be
pretty tricky.

In article <fvafa9$a2t$1@fred.mathworks.com>, Bryan <cssmwbs@gmail.com> wrote:

>i have some lines drawn on axes using the standard 'plot'
>function. now i want to use 'patch' to overlay a
>transparent shading _over_ the lines at a certain point such
>that it shades (and somewhat obscures) the lines underneath.
> here is what i have tried so far:

>figure, plot(rand(10));
>verts1 = [1 .5; 10 .5; 10 1; 1 1];
>faces1 = [1 2 3 4];
>patch('faces',faces1,'vertices',verts1,'edgecolor','none',...
>'facecolor',[.65 .65 .65],'facealpha',.25)

>while this works to shade the axes, it is not actually
>showing up as an overlay of the plotted lines. what i am
>expecting here is that the patch will 'dim' the plotted
>lines in the range [0.5 : 1]. any hints on how i might be
>able to accomplish this?

Use a brighter facecolor. For example if you change the facecolor to
[1 1 1] then you can see clearly that the lines are dimmed underneath
the patch.
--
  "Not the fruit of experience, but experience itself, is the end."
                                              -- Walter Pater

I still get nothing... (as evidenced by my post above)... I
wonder if it's a matlab version or graphics hardware issue....

"matt dash" <n.a@mail.com> wrote in message
<fvah0j$mdb$1@fred.mathworks.com>...
> I still get nothing... (as evidenced by my post above)... I
> wonder if it's a matlab version or graphics hardware issue....
>

yeah, sorry... i meant to mention i have tried a bunch of
colors, nothing works to obscure the lines. i have also
tried software opengl rendering in case hardware rendering
drivers were the issue, still not working.

i run matlab 2007b on a linux64 system with a GeForce 8800
GT/PCI/SSE2 video card. and you guys?

bryan

In article <fvaij6$s22$1@fred.mathworks.com>, Bryan <cssmwbs@gmail.com> wrote:

>yeah, sorry... i meant to mention i have tried a bunch of
>colors, nothing works to obscure the lines.

It does for me, especially as I increase the facealpha.

> i have also
>tried software opengl rendering in case hardware rendering
>drivers were the issue, still not working.

>i run matlab 2007b on a linux64 system with a GeForce 8800
>GT/PCI/SSE2 video card. and you guys?

2007a running off a linux64 system, displayed via X to an
SGI Indigo^2 Impact (from about 1995.)
--
  "It's a hard life sometimes and the biggest temptation is to let
  how hard it is be an excuse to weaken." -- Walter Dean Myers