[PD] Possible to mask a rectangle with a rectangle using GEM?

[patko]

hi again,

 after reflexion, I don't think it's a good idea to snap and apply alpha
when you want to apply a texture on the outer rectangle, some pixels might
disappear when they have the same amount of color that is supposed to disappear on the masking process.

It might be possible to apply a texture mapping on vertices drawn with openGL functions rather,
but I've no clue about how it could be done yet.
 
 Or just use the method proposed by jack that is about using four rectangles if you don't use a texture, you can connect them together like this:

[gemhead]
|
[translateXYZ -1 0 0]
|
[rectangle 0.2 1]
|
[translateXYZ 0.8 1 0]
|
[rectangle 1 0.2]
|
etc...



 Just loading an image containing the alpha hole, like attached would be cpu wise, very simple to do with an image editor,
and wouldn't add artefacts on your texture.
 I've attached an example patch and the gimp image, on gimp just draw the two rectangles, select the inner rectangle, go to Colors menu,
and then choose "Color to alpha".
 I've choosen the tiff format because it works on most platforms, unlike png.

Patrice Colet - 06 32 66 03 57 

----- "Jack" <jack at rybn.org> a écrit :

> Hello,
> 
> You have several possibilities to do what you are looking for :
> - use (as Patrick describe) two rectangles to create a mask (with
> [gemframebuffer], [pix_snap] and [pix_buffer], [pix_buffer_read],
> [pix_buffer_write]) then [pix_mask] or [pix_multiply];
> - use four [rectangle]s to build 'lines' of the rectangle;
> - use GLSL to create the mask and the final image.
> Surely, there are other ways (like openGL objects with GEM for
> example)...
> See in help > browser > examples > GEM (in Pd-extended) to understand
> what this objects do.
> Hope that helps somewhat.
> ++
> 
> Jack
> 
> 
> 
> 
> Le vendredi 11 juin 2010 à 10:03 -0700, Ryan Trigg a écrit :
> > Patrice,
> > 
> > 
> > Thanks for your reply, sounds like interesting options (especially
> the
> > snapping two rectangles together)...could you be more specific with
> > instructions on what objects to use?  Pardon my novice GEM skills.
> > 
> > 
> > Merci! 
> > 
> > 
> > Ryan
> > 
> > On Fri, Jun 11, 2010 at 9:49 AM, patko <colet.patrice at free.fr>
> wrote:
> >         hello,
> >          you can put an image texture with a rectangle made of
> alpha
> >         pixels,
> >          or draw an alpha rectangle using  gridflow and then load
> it
> >         as a texture
> >         with #to_pix,
> >          or snap two rectangles with different colors,
> >          and turn to alpha all pixels matching the inner rectangle.
> >         
> >         Patrice Colet - 06 32 66 03 57
> >         
> >         ----- "Ryan Trigg" <ryan.trigg at gmail.com> a écrit : 
> >         
> >         
> >         > I am trying to mask [rectangle] using GEM with another
> >         smaller
> >         > [rectangle] (that controls the first rectangle's alpha
> value
> >         wherever
> >         > it is placed) in order to create an adjustable rectangle
> >         outline (that
> >         > has a border of my desired thickness). I noticed that you
> >         can choose
> >         > [draw line( and [width $1( for a rectangle but the
> maximum
> >         thickness
> >         > of the line is much too small. Does anyone have any
> thoughts
> >         or ideas?
> >         >
> >         >
> >         > Or maybe there's an object like [disk] (using 4 segments)
> >         but with the
> >         > ability to adjust the height and width just like
> [rectangle]
> >         >
> >         >
> >         >
> >         > Cheers!
> >         >
> >         >
> >         > Ryan
> >         
> >         > _______________________________________________
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> > 
> > 
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