[PD] PD GEM Alpha for Two Videos

Mike Pascarella mike at pascarellamultimedia.com
Sat Feb 25 05:55:08 CET 2006


Hi Max,

Thanks for your reply.  I tried your suggestion, but changing the  
order did not change the behavior.

Mike

On Feb 24, 2006, at 11:13 PM, Max Neupert wrote:

> just a guess:
> try changing the order of alpha and colorRGB	
>
>
> Am 25.02.2006 um 04:18 schrieb Mike Pascarella:
>
>> Hi all,
>>
>> I'm new to the list, but have been using Pd for a while.   
>> Recently, I have been trying to use GEM to control the opacity of  
>> two videos.  I have found some threads in the archive discussing  
>> how to set it up, but have run into a strange problem.  If I have  
>> only one video active, I can change its opacity.  Once I introduce  
>> the second video, I lose the ability to change either video's  
>> opacity (actually, they both become 100% opaque).  Here's how I  
>> set it up:
>>
>> Video 1:
>>
>> gemhead 50
>> colorRGB (using a slider to adjust the fourth alpha channel)
>> alpha
>> pix_film
>> pix_texture
>> rectangle
>>
>> Video 2:
>>
>> gemhead 51
>> colorRGB (using a slider to adjust the fourth alpha channel)
>> alpha
>> pix_film
>> pix_texture
>> rectangle
>>
>> I do have a work-around, but I'm baffled as to why it works  
>> (obviously, I need to learn more).  If I add the following to my  
>> pd document, I can then control the opacity of both videos:
>>
>> gemhead 50
>> square (or any shape)
>>
>> Since I don't want the new object to be visible, I changed it to  
>> the following:
>>
>> gemhead 50
>> colorRGB 1 1 1 0
>> alpha
>> square
>>
>> It works, but I don't know why.  Can anyone shed some light on  
>> what's going on here?  I'm using Miller's OSX compile 0.39-2 and  
>> the latest compiled version of GEM (G4 version).  System is a 1Ghz  
>> Ti-Book with 768  Mb RAM running OSX 10.4.3. Thanks.
>>
>> Mike
>>
>>
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>





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