Author Topic: "Muddy" mask opacity problem using a Blend Node... [SOLVED]  (Read 2049 times)

Why is it that if don't use a color for the background and leave it empty, the blur gets "muddy" or dark around the edges? But as soon as I add white the edges stay pure?

Is there a way around this without using a color for the background, or another method of achieving the same effect without using the Blur node?

Thanks.

Last Edit: April 23, 2014, 04:44:17 pm

Premultiplication.

Read this: http://forums.cgsociety.org/showthread.php?t=321640

This thread might also be interesting to you. http://forum.allegorithmic.com/index.php?topic=561.0
Last Edit: April 22, 2014, 09:23:59 pm

I read both threads, thanks for that, but I need a solution to work around this. Im building an eye Substance, and I need the ability to use the Blend Node to layer each element on top of another.

As an example; the base eye color, the iris, the iris "lines", and then the pupil. They way it's currently working is that the iris and iris lines have that "muddy" effect around each which I'd rather not have. You can see from the example that the pupil and the pupil lines have that darker color around the edges where the blurred mask happens.
Last Edit: April 22, 2014, 09:38:35 pm

Hi adamz,

If you don't use any input for the background, it will be filled with a black (without opacity) color (RGBA = [0,0,0,0]).
To get a correct result, you can connect an uniform color node, set on white without alpha. This way it will remove the dark edges.
The best way to do the blending is to directly use the blue and white colors, and use the circle as a mask.
You can also connect a "level" node just after the blur and move the level in  keys to get sharper edges.
Last Edit: April 23, 2014, 12:17:51 pm
Lead technical artist
gaetan.lassagne@allegorithmic.com

Hi adamz,

If you don't use any input for the background, it will be filled with a black (without opacity) color (RGBA = [0,0,0,0]).
To get a correct result, you can connect an uniform color node, set on white without alpha. This way it will remove the dark edges.
The best way to do the blending is to directly use the blue and white colors, and use the circle as a mask.
You can also connect a "level" node just after the blur and move the level in  keys to get sharper edges.

Actually using a Uniform Color Node as white and setting the alpha to 0 fixed my problem. Thanks!