Using AE and C4D question?

[Per-Anders]

the other layers wont have alpha in them, as they're generally just layered on top of the diffuse using layering modes. i can't remember offhand if ae treats layering like this within a precomp as solid outside of the precomp or as transparent. you may want to uncompose the final precomp into your omain composition to retain the blending correctly without it appearing like it's solid over your background.

[AdamT]

If you render out of Cinema with alpha it should translate to AE as long as you output a suitable format (.tif, .psd, or .mov with millions+ colors). In the alternative you can use a comp. tag to assign your object an ID and output a separate alpha with multipass rendering.

[mbw]

Sorry for the duplicate... Opps

[mbw]

the other layers wont have alpha in them, as they're generally just layered on top of the diffuse using layering modes. i can't remember offhand if ae treats layering like this within a precomp as solid outside of the precomp or as transparent. you may want to uncompose the final precomp into your omain composition to retain the blending correctly without it appearing like it's solid over your background.

Mdme_sadie,
I tried what you said, and got it to work, but this would be an aweful way
to work if you have more than one render comp from Cinema.

However, I think I've discovered the solution and am testing it. I'll post what I find
as soon as it it done rendering. I think I made a couple of mistakes that AE doesn't
like.

Thanks for the idea.

Mark

[mbw]

If you render out of Cinema with alpha it should translate to AE as long as you output a suitable format (.tif, .psd, or .mov with millions+ colors). In the alternative you can use a comp. tag to assign your object an ID and output a separate alpha with multipass rendering.

Adam,
When I render out a .mov file with alpha everything works great. I just wanted to
learn how to take advantage of using the multi-pass render and the composition
that the importer creates in AE. There appears to be a few things that I didn't
realize about using the comp in AE. (See response to Mdme)

Thanks for the response.

Mark.

[mbw]

Okay this is so far what I've found out.

1) the continuous rastering must be on for the C4D composition for the alpha
channel to used when the composition is place in another comp.

2) It doesn't appear that any effects can be placed on this comp, because as
soon as I do, then the alpha channel is not used and I can't see my background
video.

So far this is not ideal, because I need to add "remove color matting" to the
comp, but as soon as I do, the alpha for the C4D comp is gone.

Still more to try I guess, but this work flow really seems to have great potential,
it just needs to be flushed out.

Thanks for all the help.

Mark

[Hilt]

2)
So far this is not ideal, because I need to add "remove color matting" to the
comp, but as soon as I do, the alpha for the C4D comp is gone.


Copy the layer before 'remove color matting' and then use the duplicate's matte for the layer you did the 'remove color matting'-thing (I dont use AfterFX so hopefully it works in it)

You use post effects in your scene when rendering in layers?

[AdamT]

Are you using the object pass as a luma matte in AE? That's how I do it anyway. Just put the object pass on top of the object movie in the AE timeline and in the object movie's "mode" pane specify the object pass as the luma matte.

[mbw]

Are you using the object pass as a luma matte in AE? That's how I do it anyway. Just put the object pass on top of the object movie in the AE timeline and in the object movie's "mode" pane specify the object pass as the luma matte.

Adam,
Thanks for the reply. My C4D animation is a ball flying across the screen
with pyrocluster smoke as the trail. I've created a multi-pass render and then
imported it (through the .aec file) into AE. The importer creates a C4D Composition
and I place that compsition into a new comp above a layer which contains the
background footage.

Initially the ball would not have any alpha matte applied to the composition, even
though it's properties said that the diffuse layer(bottom layer in the C4D created
compositition) was premultiplied with an alpha. Once I turned on continuous
rastering for the C4D comp layer(just above my background footage) it worked
fine.

The only other issue was a dark edge, which I would normally get rid of by
using "remove_color_matte" effect on the C4D comp layer. Unfortunately when
I did this, the alpha was lost for the layer. The solution was to remove the
at atmosmult layer from within the C4D comp.

I know this must sound confusing, but I'm beginning to think that I've missed something.
Placing multiple C4D compositions within one AE comp shouldn't be difficult, right?

Thanks

Mark

[brinda]

Adam,
...The only other issue was a dark edge, which I would normally get rid of by
using "remove_color_matte" effect on the C4D comp layer. Unfortunately when
I did this, the alpha was lost for the layer. The solution was to remove the
at atmosmult layer from within the C4D comp...


When rendering out of Cinema, use a "Straight" alpha instead of a "premultiplied" alpha to get rid of your dark finging. This type of alpha is set up for compositing. (It's in the render settings/save/ ...see attached thumbnail)

The "remove_color_matte" won't work because you can't apply effects to footage that is "Continuously Rasterized". If you don't want to re-render with a straight alpha, you might try applying your effect, then pre-comping the whole thing, then turning on "Continuously Rasterize". It's kind of a pain though, and then you end up with a bunch of un-needed precomps.

Your ideal setup might go something like this:
• Add a compositing tag w/ an "object buffer ID" to anything you want Alpha'd
• Set your Alphas to "Straight" in the render settings/save/
• Enable multi-pass, and load up whatever channels you want (say RGBa for now)
• Add the "object buffer ID" channel (with the ID from above)
• Render
** In AE **
• Import your RGBa
• Import your Object Buffer ID
• Use the RGBa to create a new comp
• Drop the Object Buffer ID render on top of the RGBa layer
• Set the Object Buffer ID layer to "Luma Matte" in the transfer modes pulldown (the pulldown with "screen, multiply, overlay, etc".
• Now just add your background footage and put it at the bottom of the comp (beneath the RGBa layer), and you should be good to render.

Hope that helps.

-Brinda

[mbw]

Brinda,
Thanks for the note about straight alphas. I'll give that a go. The only
problem that I can see from your statement is that Pyrocluster effects
in C4D don't get rendered out to an object buffer, even if you set the
emitter to an object group. I initially tried putting the ball and the smoke
in the same object ID group, but only the ball showed up in the alpha
matte. The pyrocluster effect shows up in the atmosphere layers.
(Hmmm, maybe I could pre-compose both the object matte and the
atmosphere matte and use that pre-comp as the luma matte.... Another thing to try)

One other question, why would I need to use a luma matte when the
output was RGBA? If I read this correct, RGBA is a complete rendering
with an alpha channel. Did I mis-read the manual?

Thanks for the wonderful suggestion, I'll attempt it today.

Mark

[brinda]

Brinda,
Thanks for the note about straight alphas. I'll give that a go....
...maybe I could pre-compose both the object matte and the
atmosphere matte and use that pre-comp as the luma matte)

One other question, why would I need to use a luma matte when the
output was RGBA? If I read this correct, RGBA is a complete rendering
with an alpha channel. Did I mis-read the manual?

Mark

No problem...glad to help. You're right on track with the pre-comp idea...just drop the atmosphere matte ontop of the alpha matte and set the transfer mode to "Screen". That'll combine the two, and you'll have the alpha you're looking for.

RGBa does spit out an alpha channel, but it may not always be what you want. Using the compositing tab w/ the object buffer ID allows you to create exactly the matte you want. (IE. All the spheres can be ID01, all the cubes be ID02, etc) With that many object ID buffers you can pretty much create any matte you could imagine (or even multiple variations).

-Brinda

[AdamT]

Right, RGBA works fine as long as there's only one object in your scene. Otherwise object passes and luma mattes give you a lot more flexibility.

[interactiveBoy]

You could also just use 'luminescent premul' transfer mode when you bring in items that have a premultiplied alpha. Depending on the version of AE you are using, it will be in the transfer modes list straight off (6.0+) or you will need to hold down a modifier key when clicking on the transfer mode menu(command or option I think - it's been awhile) if you are using 5.5 or lower.

[interactiveBoy]

*edit*

removed my response because apparently object buffers work differently in 9...they are actually working as alphas and do not include reflections as in previous versions. (i only recently upgraded to 9) sorry for the misinformation from me. :)

[jph]

When rendering out of Cinema, use a "Straight" alpha instead of a "premultiplied" alpha to get rid of your dark finging. This type of alpha is set up for compositing. (It's in the render settings/save/ ...see attached thumbnail)

The "remove_color_matte" won't work because you can't apply effects to footage that is "Continuously Rasterized". If you don't want to re-render with a straight alpha, you might try applying your effect, then pre-comping the whole thing, then turning on "Continuously Rasterize". It's kind of a pain though, and then you end up with a bunch of un-needed precomps.

Your ideal setup might go something like this:
• Add a compositing tag w/ an "object buffer ID" to anything you want Alpha'd
• Set your Alphas to "Straight" in the render settings/save/
• Enable multi-pass, and load up whatever channels you want (say RGBa for now)
• Add the "object buffer ID" channel (with the ID from above)
• Render
** In AE **
• Import your RGBa
• Import your Object Buffer ID
• Use the RGBa to create a new comp
• Drop the Object Buffer ID render on top of the RGBa layer
• Set the Object Buffer ID layer to "Luma Matte" in the transfer modes pulldown (the pulldown with "screen, multiply, overlay, etc".
• Now just add your background footage and put it at the bottom of the comp (beneath the RGBa layer), and you should be good to render.

Hope that helps.

-Brinda



hi there

.... but ...

so i get a nice object channel which i can use as an alpha in AE. ...sweet!

...but I also have an objectglow rendered as a post pass...
Since it is a post it is not included in the alpha...

Now that wouldn´t be to much of a problem if I would stick to AE through the entire process, but I am just suplying a an animtion which is being composed by an entirly diffrent programm into real footage...
So I have to deliver a targa sequenz rgb+alpha...

hmm with the workflow that you sugested I am always cutting out the glow...

any Idea of how two get the glow into the alpha?

ciao jan

[TimC]

if you want to add the alpha from your RGBA render to your other passes, just use the effect 'set matte' on each layer. Specify the RGBA layer for the source and use alpha. This will then take the alpha from your RGBA layer and add it to any layer you use the 'set matte' effect on.

You should not need to use the collapse transformation switch on the comp when nested into another comp. (You said continually rasterise but this switch has 2 uses depending on whether the source layer is a vector or bitmap file).

Also you should use straight alpha and in 9.5 you can specify straight alpha for the multipasses. So when you extract the alpha using set matte, you will not get the black fringing and should not need to use remove color matting.

HTH
TimC

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