alpha setting in background colour picker

hayasidist · Post by **hayasidist** » Thu Apr 14, 2011 8:59 pm

Hi.

This is NOT about rendering with alpha channel to create transparent background -- that works fine for me ... BUT ...

(ASD 6.2) If I use a "Soft Edge" fill; then render to uncompressed AVI (for use in Adobe Premiere) the background colour plus "black" is visible where the soft edge fades ... but outside the limits of the soft-edged shape the background is (as I wanted!) transparent. (i.e. the "soft edge" seems to be rendered as gradient from shape fill to background / black ... not what I wanted!!). Soft edge works fine when there's another filled shape "behind" it....

In similar idea to the thread about gradient to transparent / transparency in texture fills ... what I'd like is the ability to set alpha on the background colour picker in project settings.

(or maybe this is a Pro option?? or a bug in soft edge fill??)

Post by **Víctor Paredes** » Fri Apr 15, 2011 4:30 am

I can't reproduce your problem on 7.1
I get fine alpha on all my tests.
Can you upload your anme file to check?

hayasidist · Post by **hayasidist** » Fri Apr 15, 2011 12:41 pm

Hi Selgin.

thanks for your reply! and sorry for my slow-ish reply .. had to work out how to set up an account on media fire ... blah ...

I hope this works ...

http://www.mediafire.com/download.php?k9azx907dstdb7y

in that zip file is:

a sample .anme: bg is primary red
the AVI rendered output from that (clearly showing primary red bg)
a WMV post Premiere processing -- just 2 video tracks: that AVI "as is " -- NO chromakey etc used on the AVI input; primary green matte "behind" the AVI.

the white square over the blue is feathered beautifully; but in the WMV there is red / black in the feathering. (hmm ... ten more seconds thought here

are you going to tell me it's an Adobe 'feature'?!)

Post by **Víctor Paredes** » Fri Apr 15, 2011 2:28 pm

Ok, it seems to be a bug. Anyway, try restoring the background color to default (EAEAEA) and now render it. There shouldn't be problems. For some reason the soft edges is blended with the background when it's not gray.
I have to investigate it more, but at least you have a solution for now.

hayasidist · Post by **hayasidist** » Fri Apr 15, 2011 4:41 pm

Thanks very much Selgin.

Just as you say, a grey bg works well with a white soft edge box.

But I'm now wondering if it's a question of colour difference between bg and that used in the soft edge. I'm tempted to try a few combinations of colours of bg / "lower" shape / soft edged item.... I'll post again if I find anything significant.

But I think my original suggestion still stands ... BG colour picker to allow custom alpha as well as RGB?

Post by **Víctor Paredes** » Fri Apr 15, 2011 7:56 pm

By coincidence, I just talked about this problem at office. It depends of how the alpha channel is calculated. After Effects has special options to work with alpha, it can be solved easily there.
Sadly, I'm not an AE expert, so I can't tell you exactly where that options are.

Rai López · Post by **Rai López** » Sat Apr 16, 2011 6:26 pm

Try checking the "Do not premultiply alpha channel" check box in the "Export Animation" window, it should make a difference.

3deeguy · Post by **3deeguy** » Mon Aug 08, 2011 2:26 pm

hayasidist, A greyish fringe around the highlights of my character is clearly visible. I rendered about 1min. 10 secs. of the planet in the background so that I could composite new animation over it. I also thought compositing helped to speed up the rendering process
The spinning planet in the background was made using selgin's technique of applying a texture map to the stroke of a 3D vector. (thanks selgin)
http://www.youtube.com/watch?v=kNZaGH__eZ0

hayasidist · Post by **hayasidist** » Mon Aug 08, 2011 3:59 pm

Hi Larry.
-- did you use the "do not premultiply" option for rendering?
-- any soft edge options on the shape?
-- does the "fringe" change colour if you use a different bg colour (e.g. try primary red - does the fringe turn red?).

I've just run a quick and dirty tryout http://www.youtube.com/watch?v=2MKc0PVEXGw

rather than using texture on the stroke I've filled a shape (semicircle) (no stroke)

The AS file for the rotating planet is as in the other thread
> Group
>> Vector - Night with the "cutout"
>> Vector - 3d texture fill
>> Vector - Mask to constrain "night"

The planet alone is rendered as AVI no compression with "do not premultiply"; it's composited in premiere over 2 further layers - stars (png - with the stars as colour points on a transparent bg) and black matte. output as WMV for upload.

seems ok?

3deeguy · Post by **3deeguy** » Mon Aug 08, 2011 4:20 pm

-- did you use the "do not premultiply" option for rendering?
-- any soft edge options on the shape?
-- does the "fringe" change colour if you use a different bg colour (e.g. try primary red - does the fringe turn red?).
1) no
2) yes
3) I didn't try

Nice work on your planet. Your highlights and shadows are deeper. Even though I combined layer shadow and a gradient layer the result was limited.

I'm going to try your recommendations and report back.

3deeguy · Post by **3deeguy** » Mon Aug 08, 2011 6:11 pm

hayasidist, I changed the blending mode of the soft edge highlight to 'luminosity' which made the 'fringe' a lot less noticeable. The problem doesn't show up in the preview so I just made a 24 frame render.

hayasidist · Post by **hayasidist** » Mon Aug 08, 2011 8:51 pm

hi Larry - the key here, I think, is the "do not premultiply". this will keep the bg colour out of the render where you have drawn stuff with alpha < 100%.

thanks for your comment on the planet. It was drawn in photoshop: multi-layer (from the bottom) water; land; forest; desert; ice caps; clouds using all sorts of filters and varying transparency to give the effect I wanted - then exported as a png for use in AS. (and I still didn't fix the "join down the dateline" having transitioned from "bone-warp grid" to 3d texture...

). In the "Sorry Wrong Planet" movie I added the extra cloud layers in AS as per the other thread to give the "halo" of the planet's atmosphere. (I actually used 3 more at about 35% alpha and varying Z so that when the "ship came in to land", done using camera track from z = "big" to z = "smaller", the planet surface became progressively more visible. ) In other work I've simulated atmospheric "haze" by having many "air" layers at different z and then varying the opacity in AS as the camera approaches them. This was a test sequence from that project http://www.youtube.com/watch?v=lndB14uwkuU to try out stuff above and below a city fug. The colour bars are left unchanged throughout.