fg and alpha chanel not working well

# 1 14-09-2006 , 04:35 PM

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Location: ecuador

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What is wrong with fg and the alpha chanel? Every time I use fg and make
my back ground color iluminates my scenes, and save the image in tga. Then I open the
image in adobe photoshop, or in after effects and use alpha channel, I get a.. I dont know
how to put this on words because I dont write ENGLISH very well, I speak spanish, but
I get like a BACK light in all the countour of the objects that has the background in the back,
and dont go away with the alpha channel.
And for this reason I have to put all the things, like the sky background and that kind of
stuff in maya, and I dont want to, because there are objects that dont move like the floors or skys,
and I need to render this things just one TIME, and then use composition in after effects. Right now
I dont have a image to show you guys, but tomorrow I´ll show you what i´m talking about. But please,
I realy need help here.

kazama
raularosemena@hotmail.com

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# 2 15-09-2006 , 05:30 AM

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yea as soon as you can get an image of what's happenening (and also maybe one showing what you want to happen?) those replies will come pouring in... or maybe trickling, who knows.

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# 3 16-09-2006 , 09:55 AM

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Ok this is the image. The truck was rendered and save as a tga format. the ground the same. then in after effects, composed using interpret footage - straigh unpatted. But happends what you see. What is the problem? why the alpha chanel is not working properly.

kazama
raularosemena@hotmail.com

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# 4 05-10-2006 , 12:19 AM

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is your problem the red in the background? if the truck and the field are two separate images then it looks like the alpha worked ok. what happens when you put another image behind both the truck AND the field images? does it replace the red?

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# 5 05-10-2006 , 04:46 AM

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no its no ok, and the red background is not the problem, If i put and image it replace the red backgroun, the problem is that the truck has like a stroke, if you look close you can see it in all the truck, like a stroke in all the truck image, kind of blue stroke. my background in maya was kind of blue and if you activated FG the backgroun iluminates your scene, and when i go to after effects I cant get rid of that kind of stroke, BUT i allready find the solution.. JOJOJO

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# 6 05-10-2006 , 05:14 AM

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what did you find out?

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# 7 05-10-2006 , 05:44 AM

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What I find out was that in order that the alpha channel to work properly U have to have your background in maya BLACK, but if it is black CANT iluminate whit fg, because is black. SO what i do was make a tipical sphere like DOME object, and reverse the normals and make this object iluminate by changing the incandescense color, kind of blue to simulate the sky light, and then in the object properties (CTRL A) GO to render stats and uncheck primary Visibility, i also uncheck cast shadows, recieve shadows. I also in the metal ray section uncheck visible in transparency. Then I render, and get the ilumination of the dome thank to FG and the background color BLACK. then in after effects When i open my TIFF secuence, the program ask, if you want to ignore the alpha chanel, Straight - unmatted or Premultiplied - Matted with Color, and in this last option U get to chose a color, you HAVE to chose BLACK, and it is in this Premultiplied - Matted with color that the alpha works PERFECT, TIPICALY the Straight - Unmatted works, or so I think but dosent work to good, even with the background black the Straight Unmatted leave a BLACK STROKE in this case. SO With this I can make some nice COMPOSITIONS.. ENJOY, hope U find it usefull and hope my english was good enough

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