Trouble with fire tutorial (After Effects transparency)

[dren0chill]

hello,

i have a question on the fire tutorial.

rendering the smoke with a normal background everything runs fine

rendering the smoke without a background with an alphachannel in the first instance looks fine too

but as soon as i import the rendered clip (w alphachannel) into after effects the sprites show up with the pictureframe

i added some screenshots

appreciate your help

 

w background.tiff

w alphachannel.tiff

in after effects.tiff

[Rodney]

I converted your Tiff images to PNG as Tiff isn't a browser friendly format and folks may not want to download to see the images.

 

I'll have to refresh my memory here but... if you can supply one of the original images/frames from your sequence put into After Effects that will help.

At a guess I'd say there is a setting you'll need to adjust in After Effects but there may be something you can do on A:M's side as well.

 

Added: Make sure you are rendering out of A:M with a format that will properly save the Alpha Channel.

I recommend TGA or EXR. PNG will usually work but is not as robust a format for use with compositing.

Formats to avoid (unless you plan to add a mask to act in the place of the Alpha Channel) include: BMP and JPG.

AVI doesn't store transparency and while the Quicktime format stores the alpha channel it's usually to use image sequences.

[Rodney]

Here's an example of A:M particles (the resulting images that is) working in other programs.

 

 

Note that I used Fusion to comp the particles because it takes awhile to open and setup After Effects (doing that now).

This test also uses the PNG format (as as means to get the animated gif with transparency) so PNG does work... I just don't recommend the format if use can be avoided in the early stages. As you can see the transparency is maintained all the way through the pipeline.

 

In this test, I rendered the particles out of A:M using the TGA format.

 

Click on image for animation.

[robcat2075]

Just thinking out loud... is this the difference between "straight" and "Premultiplied" alpha channels at work here?

 

Could you post one of the targas you get out of A:M when you render with no background and WITH alpha channel?

 

(The Tiffs don't have any alpha channel)

[Rodney]

(The Tiffs don't have any alpha channel)

 

The Tiffs are just screenshots of what he is seeing.

[robcat2075]

And could you post the particle image you are using?

 

V18 has some new options regarding alpha channels and it may be necessary to set them one way to make the old tut work right.

[dren0chill]

hello,

thanks a lot for your replies rodney and robcat2075. i tried it with the exr. same problem.

untitled0.exr

 

and here a screenshot of the smoke properties

 

the before posted picture with the white background is the one coming out from after effects. it shows apart from the smoke the whole picturelayer of the smokesprite

 

thanks

[Rodney]

You might try the attached image as a sprite image and see if it makes a difference.

I note that an image from a tutorial that may be the same as yours doesn't have an alpha channel in it even though it is TGA format.

 

 

flames_v18.tga

[dren0chill]

thanks a lot,

i will try your image and check out if it makes a difference.

[Rodney]

Here's one for smoke...

 

 

The original tutorial may have used a selected key color (black?) instead of alpha channel transparency.

The key color isn't as robust as alpha channel and so was mostly deprecated in more recent versions of A:M.

smokev18.tga

[dren0chill]

rodney, thanks a lot. it looks like the problem was indeed that the picture used has no alpha channel. with your firev18.tga it works fine.

i will now try your smokev18.tga

[dren0chill]

its working but whats still funny:

as long as i do not import in after effects the rendered version with the old smoke.tga as an animation movie is smoother than with the smoke.tga with an alpha channel.

smoke_old.mov

smoke_new_1080.mov

 

[Rodney]

its working but whats still funny:

as long as i do not import in after effects the rendered version with the old smoke.tga as an animation movie is smoother than with the smoke.tga with an alpha channel.

 

 

I didn't spend a lot of time creating the alpha channel... so it's mostly just there to test the theory.

If tweaked enough via opacity etc. it turns out pretty decent though but 'as is' the images have hard edges where the alpha channel whites/blacks meet.

Sorry about that!

 

Here's part of a test I have rendering out now that uses those two images:

smoke and fire.mp4

[Rodney]

I hadn't had a chance to download your last videos.

 

I must say that I don't see much of a difference between the two.

Perhaps I did something wrong on my end downloaded the same file...

I do note those unrendered pixels are showing up here and there in the smoke and I hope that is just a fluke.

 

I've attached a side by side comparison of the two.

 

But this is mostly neither here nor there.

The important thing being that you are getting the results you want!

 

 

comparison.mov

[robcat2075]

Are we sure that smoke particle isn't a potato?

 

That has an alpha channel that is way too sharp.

 

[Rodney]

That has an alpha channel that is way too sharp.

 

Reference my post above. That was just a quick conversion of the image to test the theory that it was the lack of alpha channel that was the culprit.

We (i.e. someone with a better eye for perfection than me) will have to create a better sprite image to go with modern day approach.

The modified image (with transparency) does work pretty well with proper opacity set in the Sprite material (at a guess I'd say somewhere in the 20-33% range).

[robcat2075]

I'll note that there are three choose-able parameters to all of this that affect the outcome...

 

-whether the particle image used has a "straight" or "premultiplied" alpha channel

-whether A:M renders its frames with "straight" or "premultiplied" alpha channels

-whether After Effects interprets the frames as having "straight" or "premultiplied" alpha channels

 

That means there are 8 possible variations of the pipeline, only a few of which will give a proper result.

[Fuchur]

After Effects can do both... It is ask when importing an image sequence to it.

 

See you

*Fuchur*