Subject: Re: Transparency
From: [email-masked] (Alan Chan )
To: Multiple recipients of list <[email-masked]>
Date: Tue, 12 Dec 1995 03:45:16 -0500

You wrote: 
>
>[email-masked] (Fernando Martins) wrote:
>
>>I though I understood transparency maps, but I think I don't :(
>>
>>I have two overlaping polygons with two different image maps. I don't 
wnat to
>>see any edge in the final image... The image in the front polygon has 
black
>>borders (the image is bright in center and fading to black) and 
altough I use
>>the same image as a transparency map, I can still see where the front 
polygon
>>is. The best I could do was to make the front polygon be 
half-transparent
>>in the black areas, but I still see the edges :(

Several things could be a problem:

i) you have specularity or some other surface channel on. Even if an 
object is 100% transparent it still has a specularity value.

ii) Your black is not true black (0,0,0). Check to make sure your edges 
all fade to 0,0,0.

iii) You should paint a specific transparency map or use a high 
contrast image for the transparency map. If you use the same image, 
parts of the image may also appear slightly transparent.

Of course, not knowing the specifics of the scene, it could be 
something completely different. :)

AC