[Bf-cycles] Alpha pass independent from transparent option

[Brecht Van Lommel]

Hi,

On Sat, Dec 8, 2012 at 7:45 PM, Adriano Oliveira <adriano.ufrb at gmail.com> wrote:
> Consider this scenario: In a outdoor render, I have ground, buildings and
> trees (leaves have oppacity masks), and a sky. In the composition I want to
> compose the render with an AO pass. Without an alpha to mask AO, the sky
> would get black. I canot use masks based on objectID, due to leaves
> transparency...
>
> In this case, using alpha mask is just fastest and the fring pixels are no
> matter at all.

In this case you should set the film to transparent, multiply AO with
the combined result, and add the environment pass afterwards. If the
background is blue and the leaves are green, only the green component
should get darker. There may be no fringes but the result would still
be wrong, how noticeable that is depends on the specific render of
course.

Brecht.