Material/Image with transparent background

[Steve Seeley]

Basically I need help getting rid of the fringe produced by the alpha channel. You would think that if you had a photoshop document with a transparent background, it would create a perfect alpha channel, but it’s far from perfect.

I’ve read that version 10 seems to fix the problem, but has anyone found a solution for v9?

[Ronaldo Montalvo]

read all this thread perhaps:

https://forums.creativecow.net/readpost/19/859867?

[Govinda__]

This is more about Photoshop than Cinema.

I don’t trust the psd format. By default, photoshop format is premultiplied, i.e., the alpha is in each of R, G and B and you have multiple alphas for special purposes such as layer masks. You can see that it’s premultiplied by looking at your channels–they each have transparency. Try giving your image an actual channel alpha, which is to say a ‘straight’ alpha image and save it as 32-bit targa file. Then load that into your alpha and see if the problem doesn’t go away.

I’ve still had this problem with a targa, but only once in two years since I started using that ancient, reliable, rock-solid format (it dates from 1983!). In that case, three months ago, I went back to photoshop and ‘choked’ my matte–loaded the layer as a selection, contracted it or expanded the selection as needed and resaved that as an alpha.

[Steve Seeley]

Saving with an actual alpha channel doesn’t fix the problem. And the matte can’t really be choked as it gets to thin and starts to deteriorate. Playing with the color and delta settings changes the choke settings a bit, but it’s fairly unpredictable and seems unreliable.

I’m pretty sure the photoshop format isn’t really to blame, as it works with pretty much every other graphic app out there. It’s c4d that doesn’t interpret it’s transparent backgrounds properly.

Is there a way that a fully vector illustrator file could be used with a transparent background instead?

[Govinda__]

If you say so… Last thoughts for troubleshooting. Change your sampling to SAT. Put a compositing tag on the object with forced antialiasing of 1×1 and 4×4 at least. Reread the c4d manual section on the antialiasing types (circle, sync, etc.) and why they’re there and in which situation you use them. Most importantly in photoshop copy the layer to a fresh document and resave that with straight alpha. Try it as a Tiff.

I’m sympathetic because I’ve had this problem. Okay, it was once in probably a thousand cinema 4d project files, but I’ve had it. I didn’t have to go to extremes to solve it because choking worked. And no, I don’t agree that the premultiplied photoshop format is rock-solid across all apps. I’d change my mind if I heard of well-sourced arguments otherwise, but until then, if one image format that’s screwed me in the past risks screwing my 12-hour 2,000 frame render and costing me a missed deadline, you know, for my part I’m not inclined to use it. Same goes for jpeg–I haven’t used that format in textures since multiple texture errors in 2004.

[Steve Seeley]

That’s cool, thanks for all your suggestions. I will try SAP sampling and look into the different anti-aliasing modes. I guess the photoshop format has always worked well for me, so I am quick to come to it’s defense… haha. I really appreciate your comments.

Cheers!

[Ronaldo Montalvo]

don’t take offense but i think you might still have something wrong. photoshop files will work fine in c4d with no fringe and no need to choke if done correctly, and i don’t think SAT will make any diff for the alpha problem.

are you sure you’re getting the settings actually selected in the “Layerset . . . Select” tab under the alpha shader properties? if you save the pshop file with no bg (checkered bg shows) and without a separate alpha channel, load the pshop file into both color and alpha of c4d material channels and in the alpha “choose layerset” pane use the first entry: “layers/layers sets” and check ‘generate alpha” then make sure you actually select and hilite the layer 1 (it turns yellow) that appears in the pane below. it should be clean with no-fringe if the phsop layer is clean, works for me at least.

[Govinda__]

Actually when it last happened to me, the file originated as a couple of jpegs (one file rgb and one alpha) that I made into a premultiplied psd. The worst of it was a line at the top of my imageplane that I couldn’t get rid of.

[Lennart Wåhlin]

As mentioned above, It is solely a Photoshop issue. Cinema only uses whats there.
I seldom have problems using Multiplied apha out of PS but when it gets critical
straight alpha must be used. Problem is, PS (CS 1 at least that I run) doesn’t make straight alphas out of the box.

For making multiplied alpha in PS:
Make your art.
Make a selection of the emty area.
Create a new channel(alpha)
Invert selection and cut the alpha layer.
Create a new -black- layer under your art.
Flatten the picture.
Save and use in Cinema.

For Straight alpha in PS.
Go to:
https://formfilms.com -> Downloads
and get the “straight_no_ice” action script.
Run the script directly on your art layer.
(I think it by defalult makes a tiff, but I’ve changed to .psd in the action script myself).

In both cases, select the alfa layer in the alpha channel settings in Cinema.

Cheers
Lennart

[Steve Seeley]

Unfortunately in C4D v9.1 there is no “Layerset . . . Select” tab in the alpha settings. I suspect that the newer version solves this issue, so it’s probably time to upgrade.