I noticed when I rendered a pic in P7 (from a P6 scene I made with a background image applied) the image export is missing it's alpha channel.  It works just fine in P6, but P7, no alpha.

Doug

That's odd - I'm rendering a scene built in 6 (that P6 wouldn't render) and it has a background image including the alpha channel.  Of course, I opened it in P7 and saved it immediately so that P7 would recognize everything.  Maybe you could try that?

does your P7 RENDER have an alpha?

Yes - and everything is working fine.

I havne't had any problems with alph channels either. But then I always save as Tif. What format did you use, Sturk?

12/19/06

Victoria_Lee, TrekkieGrrrl:

Can you export at higher than 72 dpi in any file format? I can't. (:-{(

LMK

LMK,

I export all of my images in .bmp and .jpg formats at 4800 dpi

Native PSD format.

Doug

12/19/06

Sturkwurk:

I am not nearly clever enough to know how to use the alpha channel, but everything I export from Poser 7 comes out 72 dpi, no matter at what dpi I render the scene. When I open the image in another application and check the properties it always comes out 72 dpi. Is there some setting somewhere that I am missing. Poser 6 on the same computer does not do this.

LMK

Alpha channels have nothing to do with resolutoin.  If you have a more advanced photo editor, you can see channels (usually a red, green, blue channel and an alpha - Alpha are great to use for making image masks)
pngs (sometimes)
psd
tif
formats all can have an alpha channel.  Poser 7 is not creating one like it should be if there's a background picture - Poser 6 makes them just fine.  (I havent tried tiff yet - but that's a work around I may have to do for now)

Doug

I haven't tested psd, but I've had no trouble with Alpha channels and my tifs (to reiterate what has already been said, I guess.)

When I first got P6 a few months ago I got some really messed up Alpha channels on a few renders.  I complained a blue streak at Contentparadise, then suddenly I didn't have the problem in anymore renders.  I keep expecting to see it again.  Ever since I left P5 it's been like sleeping with one eye open.  Sure, on the surface these new versions look better, but I don't trust them yet. lol.

I tried Poser 6 with a background image and I got an alpha channel around the subject in the front of the background image. Didn't know that could be done.  In Poser 7 I opened the same file and I get an alpha channel that is a solid block the size of the image which I believe if the same behavior of earlier versions of Poser, except version 6. I don't normally use background images because I couldn't get an object out of the image with the alpha channel, so I never even tried that in Poser 6. I'm saving in psd format which is my usual.

lkendall, In the Render Dimensions settings, you can change the default 72 dpi setting if you select "Render to exact resolution".

I was wondering about this alpha channel problem, so I did some meager testing using the default factory scene rendered with the default Firefly settings. Now remember, this topic is regarding alpha channels from P7 renders with background images. Initially, the PSD and TIF alpha channels were showing up when rendering w/o background images. But that's not the issue. I made some renders WITH background images and no alphas! I deleted the background image, and subsequent renders also had NO alpha channel, whether they had BG images or not. I quit P7 and restarted, rendered, and alpha channels worked again. I tried the "Paste onto Background" feature, rendered, and the alpha was fine. I deleted the "Paste onto Background" image, and tried another via File>Import>Background Picture. Once again, rendering with AND without BG images, no alphas. I closed the file, and made a New file, rendered the factory default, and alphas were back. There definitely seems to be a problem with P7 befouling alphas thanks to BG images, but I can't pinpoint why. Any thoughts? Edit: Mac G5 Dual 2.5 GHz OSX 10.4.8 8GB RAM

Sturkwork, there is deffinately a bug and it is in the tif settings aswell.

The test I had done before was with no background.  But when I choose a background image, the Alpha is solid, no deliniation.

I just did a little test and saved in both tif and psd and the alpha was the same in photoshop in either case.

Damn!

Well, time to report it.

Glad to see some confirmations!

looks like a bug to be fixed.

Doug

Any news about this bug?

I like to render over photographs and the working alpha channel is a great tool when doing postwork.

I've been out of the loop for a while, so apologies if this is a dead horse!

They seemed to have called it a feature and somethigng that is desired if I remember right. There is some kind of odd work around but it was posted at the contant paradise forums and I didn't pay it to much attention because it kind of irked me.

Quote - Alpha channels have nothing to do with resolutoin.  If you have a more advanced photo editor, you can see channels (usually a red, green, blue channel and an alpha - Alpha are great to use for making image masks)
pngs (sometimes)
psd
tif
formats all can have an alpha channel.  Poser 7 is not creating one like it should be if there's a background picture - Poser 6 makes them just fine.  (I havent tried tiff yet - but that's a work around I may have to do for now)

Doug

Actually P6 was doing them incorrectly. An alpha channel is an associated image where there is a value for each pixel of 0 where there is no image coverage, 1 where the coverage is full, and fractional values where the coverage is partial. In P6, background images were treated essentially as background colors, so the alpha channel ignored them. In P7, they are treated correctly (or at least consistently with other applications), as actual parts of the image. P6 didn't handle alphas correctly. Imagine a half-transparent glass ball rendered without a background. The alpha would have values approaching 1 along the edges of the ball (as seen by the camera), and 0 toward the middle where there is less glass thickness. If I composite the ball with a red background, the ball appears red (with lighter red edges), if against a blue background, it appears blue. 

In P6, if you render the ball against a blue background, the alpha channel will be 1 where the b all is and 0 everywhere else, and no matter what background you composite the ball against, the ball will be blue.

Essentially, the P6 alpha channel is just a mat selection of the non-background portions of the scene.

Quote - Any news about this bug?

I like to render over photographs and the working alpha channel is a great tool when doing postwork.

I've been out of the loop for a while, so apologies if this is a dead horse!

As I discussed in the above, it isn't a bug. What I would recommend is to use the background for composition, and then perform two renders, one without the background (just make it transparent), and one with just the background, and then composite them. It's a bit of a pain compared to what the workflow is in P6, but it has the following advantages:

If you decide to change the background (make it black and white, use a different background etc.) the clear parts of the objects in the render will show the new background, not the old. Also, there won't be a halo effect around the edges of semi-transparent objects such as hair. (Before, if you rendered dark hair against a light background, and then composited it against a dark background, the hair would have a light halo around the edges where it had partial transparency, and the image would have picked up some of the background.

Ahh I see, thanks very much for the reply AnAardvark!

There's just something that baffles me then, maybe I'm missing an entirely obvious feature (which is very likely). When I do render without a background (with just any random background color) and then export it as a .psd, open it in Photoshop and use the alpha channel to select the rendered character, it retains that halo as you call it.

So if I render in Poser with a white background and decide to composite it onto a black background later, there will be that white outline, about 1 pixel wide around the entire figure. I've always struggled with that, but if I understand you correctly, there's a way around it?

Quote - Ahh I see, thanks very much for the reply AnAardvark!

There's just something that baffles me then, maybe I'm missing an entirely obvious feature (which is very likely). When I do render without a background (with just any random background color) and then export it as a .psd, open it in Photoshop and use the alpha channel to select the rendered character, it retains that halo as you call it.

So if I render in Poser with a white background and decide to composite it onto a black background later, there will be that white outline, about 1 pixel wide around the entire figure. I've always struggled with that, but if I understand you correctly, there's a way around it?

I'm not sure. I haven't had that problem in P7. I usually render using ray-tracing. It's possible that your render settings may be a problem, especially if you are using the option which does pos-trender smoothing. (I can't remember off-hand what it is called.)  Which version of Poser are you using? I think that prior to P6 you are stuck with the halo, even if you are using just a background color.

I'm using P7 as well. I almost always render with ray-tracing and smooth polygons on.

I'm rendering some test images right now to illustrate my problem.

Could it be the post filter you're thinking about? I always leave that at the default (box, 1). I made a test, setting it to 3, which made the white halo/outline more obvious, but as you can't set it to 0 or turn it off otherwise (that I can see), I don't know...

The test below shows my predicament. It's been rendered in P7 with a white background color, then exported as a .psd, brought into Photoshop (CS2), where I selected the alpha layer (holding CTRL down and selecting it, then going back in the layers mode and copying the selection from the Background layer onto a new layer and then inserting a black layer in between to show what happens).

Is my method of selecting the alpha layer where I mess up? Maybe I'm doing that step wrong.

Anyways, here's the image:

Thanks again for the time!

(Sorry for hijacking the thread Sturkwurk, I'll start a new thread soon, but it seemed relevant somehow hehe).

The Halo problem is exactly why I liked having the alpha channel and background image option.

In P5 I would render over my selected background image, but I would also get the Alpha info without the image being there.  This allowed me to mask out my foreground subjects and add things to the background or to adjust colours and such without effecting the foreground and vica-versa.

Since I rendered over what was mainly going to be in the background I could negate the halo effect in most situations.

Oh well, if this isn't a bug, but instead a "desired effect", then I just have to get used to a new workflow.  Which I have been employing anyway for the most part.

Quote - The Halo problem is exactly why I liked having the alpha channel and background image option.

In P5 I would render over my selected background image, but I would also get the Alpha info without the image being there.  This allowed me to mask out my foreground subjects and add things to the background or to adjust colours and such without effecting the foreground and vica-versa.

Since I rendered over what was mainly going to be in the background I could negate the halo effect in most situations.

Oh well, if this isn't a bug, but instead a "desired effect", then I just have to get used to a new workflow.  Which I have been employing anyway for the most part.

Also worked that way in Poser 4 too!

But with the new workflow hmmmm first render the foreground figures with NO LIGHTS and NO BACKGROUND.  Save that image as a PSD - you can use the MASK from the alpha in your FINAL image!!  Just drag that alpha into the other doc!

Doug

Quote - The Halo problem is exactly why I liked having the alpha channel and background image option.

Same here! But as you say, will just have to find another way of doing it then.

Quote - But with the new workflow hmmmm first render the foreground figures with NO LIGHTS and NO BACKGROUND.  Save that image as a PSD - you can use the MASK from the alpha in your FINAL image!!  Just drag that alpha into the other doc!

I'll see how this works out, thanks!

Anybody notice the problem's been fixed?  I just did a poser 7 render with a background image and I got a great alpha channel just like I used to in Poser 6.

Doug

I went to just rendering over Black, then saving as a .png to get perfect transparency around hair and such. That seems to work quite well, especially if you change your mind as to what kind of background to use later on.

Quote - I noticed when I rendered a pic in P7 (from a P6 scene I made with a background image applied) the image export is missing it's alpha channel.  It works just fine in P6, but P7, no alpha.

Doug

There are several threads both at CP and DAZ regarding alpha channels and rendering over background.  PSD and TIFF used to give you an alpha channel when rendering over background.  However, in P7, EF "fixed" this.  According to UliK, all versions prior to P7 handled this "incorrectly".  P7 now handles this "correctly".  Or so say the EF Render Police. 

Here's the CP thread with the EF answer:

http://www.contentparadise.com/forums/showthread.php?t=4131&highlight=alpha+channel

And the explanation from the EF website:

http://www.e-frontier.com/article/articleview/2137/1/858/