In Cararra, is there a way to save a foreground image as a layer which can then be superimposed over a background image?

If I get too much detail, too many objects, into a scene it becomes unwieldy.  Rendering the background and then the foreground seems a good workaround.

A jpg with no background saves with a black background.  The true transparency of a layer is needed for a realistic overlay.

Klebnor

 It's a very old, common trick in CG - especially for animation - going back to the early days of Disney.

Build your scene in groups that you in fact, use as layers. Simply hide and reveal groups/layers as needed to work on your scene to gain speed enhancments. When it comes time to render, you can turn on a single group/layer enable premultiplied alpha, and then complete the rendering. Obviously, you'll need to do multiple renders for each layer. However, this gives you incredible control over lighting and depth of field that can then be done in post render.

A great diary of how this was done with Carrara/raydream has been the very slooooooooooooow progress of Rustboy. I don't know if he is even using Carrara anymore for his renders but he did for the original sequences using the process that I described. You can check out his work at this link.

Mark

You need to use the Render Alpha Channel option in the render room (Output tab) but it will only turn on when you choose a file format that support alpha (like PSD or Targa).

  I am having the exact same problem.  As a matter of fact, the scene I am trying to get to render before the Holiday contest ends is the current issue.  I cannot render the scene in it's entirety.  I decided finally to seperate it into 2 or three seperate renders.  To start I am doing a render of just objects which are outside the of the rooms window.  Next I will do the inside objects and walls.  Lastly I will render the actual figures.  Then I can just layer them one on the other.  I will use the outside scene render for a backdrop when I render the room itself, then I will render it and use that render as a backdrop for the figures.  I will have to do some messing around with the shadow and liminance map, but it should work out.

Quote - In Cararra, is there a way to save a foreground image as a layer which can then be superimposed over a background image?

If I get too much detail, too many objects, into a scene it becomes unwieldy.  Rendering the background and then the foreground seems a good workaround.

A jpg with no background saves with a black background.  The true transparency of a layer is needed for a realistic overlay.

Klebnor

I have that feeling that something is right before my eyes but I can't see it. I've been hunting around trying to figure out how to make the background of a scene render transparent when I found this thread and thought I would tag onto it.

According to what I read here and elsewhere I understand in order to have a transparent background I need to use an image format that is capable of displaying the alpha channel.

With that information I started with a brand new blank scene. I placed a sphere on the scene and applied a simple texture. I made no other changes or adjustments until I got to the render room.

In the render room I first set the file format to TIFF, which displays the alpha check boxes. I checked both the "Render Alpha Channel" and the "Use Premultiplied Alpha" check boxes. Rendered the single frame and got a sphere with a solid black background.

I attempted the same settings with the file format set to GIF with the same results. I also tried unchecking "Use Premultiplied Alpha", still with the same results.

I am at a loss as to what it is that I might be missing. Can someone please point me in the right direction. thanks

 The alpha format is not respected by all output options. In fact, only the .psd, .rpf and .tga will honor it. The newer .tif formats will support alpha info but Carrara does not export to those formats. 

As for .gif, it has it's own transparent background option but tI can't take a look for right now because I have a render going! However, I've found finessing .gif transparencies is usually easier with something like Photoshop because you end up with smaller file sizes which is kind of the point of .gif web files anyhow!

Mark

The little sphere test I just did I got no alpha channel w/ targa and one w/ tif. hmmm.
Didn't have the 32bit option for targa checked. That did it. I actually did get an alpha channel for both formats tho.

Are you on a mac or pc? I suppose it is possible the mac tiff format doesn't support alpha. This is on a pc.

 Excellent news on the .tif then. I hadn't tried it for some time since I typically use .psd or .rpf.

Yeah, both C5 and C6 have it.

I have now tried all the available output formats available that display the alpha checkbox, TIFF, TGA, GIF, and PSD. With each I still am unable to get a transparent background. I'm beginning to think I'm crazy because I keep trying the same thing expecting different results lol

Is it possible there is some other configuration setting I need to set? Again I've open up Carrara, placed a sphere in the work area and gone to render. I've touched no other settings. I am using Carrara 6 pro.

Your issue maybe the program u r opening them in doesn't support channels so you can't see them. The alpha is a channel not a layer. Gimp is free and it reads channels and easily converts a channel to a layer.

Yes the question now is what 2D software are you using?

I'm using Photoshop CS4.

 Well, that should work for you. ;-) Simply open the channels palette, use the alpha mask/channel to create your selection and then delete the background. 

Carrara, like most 3D software, doesn't provide an actual transparent background in the finished render. However, also like most 3D software, it does provide the channel and selection tools to remove the background. 

Mark

Ok, kind of sounds like it has been working just my expectation of what working means is off.

Most of my experience is in Poser and doing animation. My normal work flow has been to create the animation series in Poser and then render to a file sequence, normally PNG. Then import that file sequence directly into a layer in After Effects or Flash. In many cases I have a transparent background in my animation layer and then use another layer to provide the visible background.

I have limited experience with Carrara but have been working on an animation that involves a lot of camera movement around the scene. I've found Carrara's abilities in that area to be superior to Poser which is why I was trying to use it there.

It kind of sounds as thought while Carrara can output a transparent background, it requires some additional manipulation in Photoshop or something similiar and may not be completely practical for my normal workflow as I have described it. Is that a correct assumption?

I very much appreciate the help, thank you!

 If you import a sequenced .psd or .tga file into AE, it will acknowledge and work the the alpha channel. The .tga format has the alpha channel "embedded" as a transparency channel like the .png format does. Carrara doesn't export .png though. So, to get that same functionality, simply export a sequenced 32 bit .tga