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

[cyrille henry]

hello,

i may have misunderstood the question, because i think there is a much simple solution using rendering order.
see attachment.
c


Le 12/06/2010 07:05, patko a écrit :
> 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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