[tom]

As Mihai said, we've tried to prevent users produce incorrect pair of images because it was a common mistake but when we let this happen, then the users post images telling they have edge artifacts in compositing. If any of you have a working example of the feature you're asking for, please feel free to demonstrate with the images.

[b-kandor]

Thanks for the video tom - very useful!

Kandor

[leoA4D]

That is a good discussion but, we need to summarize for the one "thick-as-a-brick" user (me):

At this time, the following methods of rendering the RGB and alpha (and material id and object id) channels are recommended:
The more correct procedure: render each channel separately.
The less correct procedure: render all channels together.

Is this right?

Thanks for the patience.

[tom]

Is this right?

No, what you say is wrong. Go through this thread once again.

[b-kandor]

That is a good discussion but, we need to summarize for the one "thick-as-a-brick" user (me):

At this time, the following methods of rendering the RGB and alpha (and material id and object id) channels are recommended:
The more correct procedure: render each channel separately.
The less correct procedure: render all channels together.

Is this right?

Thanks for the patience.

I think the point is - if you want to composite in the background then you check alpha at the same time you render, that way the sky will be multiplied black so that (as tom's video) shows you get correct antialiasing between your scene and your background. Plus it's faster doing them together anyhow.

[leoA4D]

Thanks, b-kandor. That is what I have been doing with the new Mac update.

This is why I am finding this difficult:

"The first render, render only the color image, no alpha. The second render, check only alpha, and uncheck the main render. This way it takes the same time as if you had rendered everything in one go." -Mihai

"...and yes, the interleaved mode is rendering faster than you render them apart. Sorry for the confusion." -Tom

"Just to be absolutely clear, if you will have this option (to render sky and alpha at the same time), don't expect your alphas to crop out the image as you expect. You are basically asking for an option which will provide an incorrect alpha cutout, which will make edges appear where the sky color blends with the edges of an object." -Mihai (my underlining)

[b-kandor]

Thanks, b-kandor. That is what I have been doing with the new Mac update.

This is why I am finding this difficult:

"The first render, render only the color image, no alpha. The second render, check only alpha, and uncheck the main render. This way it takes the same time as if you had rendered everything in one go." -Mihai

"...and yes, the interleaved mode is rendering faster than you render them apart. Sorry for the confusion." -Tom

tom was correcting the first statement by Mihai

"Just to be absolutely clear, if you will have this option (to render sky and alpha at the same time), don't expect your alphas to crop out the image as you expect. You are basically asking for an option which will provide an incorrect alpha cutout, which will make edges appear where the sky color blends with the edges of an object." -Mihai (my underlining)

Right, Mihai is saying "if the option existed (that people were asking for) of simultaneously rendering the image with sky and generating the alpha map, then that alpha map would not function correctly because the sky color would be blended to the object colors and the alpha mask wouldn't be able to crop it out correctly.

So basically, everything is perfectly fine, render with alpha simultaneously and composite using the method tom shows in his video.

[Mihai]

Leo, I was wrong in the first post, there were optimisations done afterwards so that the render and alpha rendered together render faster. When you render alpha+render together, the sky is rendered black, to avoid problems later with the objects containing colors from the sky at the AA edges, or even heavier problems when you have dof blurred edges.

[leoA4D]

All is good. Thanks guys.

BTW, good video Tom (corrected, my bad). Something similar here: http://www.maxwellrender.com/forum/view ... ight=alpha, Michaelplogue's page 2 Q&D tutorial.

[Jozvex]

but i think this should be an option for people that need both the alpha and the sky's color for post-work (even with this draw-back).

A fast way to do that (if you want to adjust the sky colour in post for example) would be to render a separate sky image, with no geometry in it. That should clear up really fast.

[joie]

I want the old method back, it can be the wrong method, but is not anything photoshop "defringe" tool can´t remove..., as easy as that.

Instead, we have to wait the postprocessing stage to see a near finished image..., that´s not good for me.

[deadalvs]

The first render, render only the color image, no alpha. The second render, check only alpha, and uncheck the main render. This way it takes the same time as if you had rendered everything in one go.

i had not thought of unchecking the color pass. such small things rock my world !

thanks, Mihai !

[rivoli]

What will be the prcedure to compsite series of images in other postprocessing software (After Effects/Premiere, Flame/Smoke etc) without Photoshop's "remove black matte" option?

this is exactly what the whole idea of rendering against a black background it's all about. as tom and mihai have said: it'll give correct results in any compositing software.
you don't need any ps specific tool to comp an image over a background (actually ps really sucks when you start dealing with alphas and mattes). any compositing package will perfectly work with rgbs and alphas out of maxwell.
premiere it's not one of them though

[tom]

Rivoli is right and today even PS and Premiere has additional matte support for compositing. We did not invent anything new, just our previous approach was incomplete. The following article will be a good guide for everyone to learn more about alphas/compositing, why and how...

http://www.itbusinessnet.com/articles/v ... d=135386-0

The problem is that not all of us are using Photoshop. Matte without removing black edges is unacceptable right now.

Doesn't matter, PS is one of the weakest in this area. I made the video tutorial using PS because it's the most common and it works. I know many but don't know any other compositing software which doesn't support the most basic feature "removal of black matte". Which software do you use for compositing not supporting this?

2. What about half transparent objects (glass matte is completely opaque now)?

Alpha supports transparencies. You should render a transparent object against environment space (could be sky, none, image based...) to see transparency in alpha.

[leoA4D]

Alpha supports transparencies. You should render a transparent object against environment space (could be sky, none, image based...) to see transparency in alpha.

Good timing on this info. I have an exterior glass rail and am rendering it now. I need to confirm I am doing the right thing:

/ I rendered the RGB, Alpha and Object Id channels with the glass hidden.
/ I am rendering the glass visible with everything else hidden from camera, both the RGB and Alpha Render Channels checked to make the AGS glass transparent and Physical Sky is selected. That much I hope is correct.
/ Lastly, and I have not done this before, I will be using the RGB and Alpha channel renderings in the compositing with the layers without the glass.

And a question, do I need to run the glass only (RGB) render as long, +/-, as the original render (without glass)? Just trying to judge since the glass is difficult to assess when the background is black.

If I am not doing this right, please provide some details of how to get it back on the rails.

Thanks.