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

[Ryan Trigg]

Thank you to all for being so helpful!  Cyrille, that looks exactly what I'm
looking for.  I can stop pulling the hair out of my head.

Thanks again everyone.

Cheers!

Ryan

On Sat, Jun 12, 2010 at 2:23 AM, cyrille henry <ch at chnry.net> wrote:

>
>
> Le 12/06/2010 11:17, Jack a écrit :
>
>  Yes it is working fine ;)
>> I thought about a solution without the translation.
>>
> without the translation, it could work, but i'm not sure the result will be
> the same on every GPU.
>
>
> c
>
>  This is a nice example for the importance of the rendering order.
>> ++
>>
>> Jack
>>
>>
>>
>> Le samedi 12 juin 2010 à 09:25 +0200, cyrille henry a écrit :
>>
>>> 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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