Alpha Chanel in Carrar 5

[glider161]

Hi, I have been using Raydream Designer for years until my old Mac died. I have recently experimented with Carrara 5 but am going nuts with rendering. I render a scene with the "render alpha channel" selected. However, when I load the channel in Photoshop it only selects the background, not the rendered object. Carrara is extremely similiar to Raydream and I never had this problem. The manual is of no help. Can sombody give me a hand.

Thanks,

Bruce

[jamesmc]

I don't use Carrarra but my guess is that some how there is a switch in Carrara that tells the alpha channel what to do.

As you know the first 24 bits are 8bit Red 8bit green 8bit blue.

In Alpha Channel, it can be 8 or 16 bit.

Alpha Channel can provide a mask such as all 1s (white) or 0s (black) to make it easier for applications such as video or graphics editors to identify the mask.

If you are trying to render to a graphics program that doesn't support Alpha Channel manipulation it may not show up.

If you are rendering to a video, there are some types that support Alpha channels (Quicktime and WMV, etc.) and some that don't (older Flash, JPEG image sequence, GIF.)

I would examine the render output and to see if you are asking to render a transparency or a mask. Should be in your literature somewhere.

[gidgit]

I do not have C5 at my disposal, so I am not sure what is or is not documented, however I do have the Carrara Studio 2 manual right here in front of me, and it there is some info on this within the Rendering Chapter, under the heading of G-Buffers

it suggests that pixel color occupy's channels 1,2,3 for red, green and blue, and that Carrara puts the mask data in channel 4, the Alpha channel.... your 2d apps should have the masks in this channel as well

hth's

(good stuff jamesmc)

[Grafixman]

If it is being opened with the background selected in PS, then perhaps you could then invert the selection and extract the object by copying and pasting the inverted selection on a new layer? Or perhaps deleting the selected background after promoting your picture to a layer?
Or perhaps you have something else in your background, like a ground plane, which is also getting rendered and exported?

[jamesmc]

heh, thanks gidget...

That's about as deep as I want to get into it.

All those times in physical chemistry lab burned out my brain on wavelengths, doing mathematical formulas to convert color spaces from RGB monitors to make quantitative and qualitative analysis of blah blah blah...

My eyes still get crossed thinking about it.

[Mike Bailey]

In Photoshop, to determine if an alpha channel is included in the file, click on the channels tab, you will see an alpha channel at the bottom of the list, it should be a greyscale image. To make the alpha channel a selection you select the alpha channel so it becomes active then click on the "load channel as selection icon", Switch back to RGB, then back to layers, the selected pixels will be from the alpha channel. invert selection if you desire.

If you are doing multi pass rendering and the alpha is a separate greyscale image file, then you copy and paste it into the RGB renders alpha channel so it can be used as a selection.