Cineversity

Hi there

I’ve modelled a book in c4d. I want the text to disappear as the scene goes on. To do this I’ve used two materials on the page: the first one is the material for the actual paper. The second is the material for the text with an animated alpha channel created in AE.

To be able to add some effects to the disappearing text in AE I would like to export this materials alpha channel as a separate pass but I haven’t found the way to do it yet.

Any ideas?

Cheers

Steve

Hi Steve,

Since you have two materials, the object will be opaque.

Let me suggest a few ways to do it.

Work with a double page, while the text is on a slightly elevated page (via Displacer). The text has for rendering the same color as the page itself. It will be set darker based on the Object Buffer for the upper page (in Ae). Otherwise, you have no information about the paper texture. (Set the Compositing tag to: cast no shadow for the top page!)
Scene file:
https://www.amazon.com/clouddrive/share/MP9MQve1UM9NnT7sIU1JNgSwVvB1dlHqQqK4WCXuCru

You render just twice, one time with and one without the text. Here one can work even without any Alpha or Object-Buffer. Both results are composited on top of each other, and the transparency setting for the top layer is adjusted, perhaps even with a mask. To render this out, maybe consider the Takes option.

You can render as well an UV-pass out and use the RE:Map plugin from RevisionFX, which allows placing the text later onto the pages (use at least 16bit/channel.)

Let me know if there is anything else, I’m happy to look into it.

My best wishes

Hi and thanks alot for the quick reply!

However the file you linked is not the one you mention with the double page. Could you upload that one so I can have a look at it?

Thanks!

All the best

Steve

Thanks for the reply, Steve.

I have fixed the link, sorry about that, and I have checked the shadow option for the file below:

Scene file
https://www.amazon.com/clouddrive/share/Wo9Lij6fhwvPNH7KWL8qbsfWpYdZuoI7JmqCAwoBMKp
I have used a checkerboard shader instead of text.

Screen capture
https://www.amazon.com/clouddrive/share/bpmFH3FlfNWHD3jtOZ5M5lFPSE95KJFDRRKarl7yk6c

For other workflows:
Other methods, in which you render things out twice, can be done quickly regarding the second pass. Alpha channels as well Object Buffer, have no need for any light or shadow calculations. In return, the second pass will be fast. The Takes system allows to set those up, as mentioned before.

Cheers

Hi Dr Sassi!

I’ve looked at your file and was able to rebuild everything from scratch in a new c4d file. However, I haven’t managed to use this technique in my original file and I haven’t found the problem yet.

I’ve attached a lightweight file (without the png sequence for the text, put a checkerboard alpha-texture in there instead) where you can see what happens when I render.

Thanks for you help once again.

Steve

https://www.dropbox.com/s/kt186x39hmf1daa/book_with_deplacer_for_alpha.zip?dl=0

Hi there

I just found out that it’s the Ambient Occlusion that’s messing up stuff. With is deactivated, the Text renders out as an alpha channel.

Any possibility to get some AO anyways? Render an AO pass with the Text Plane deactivated I guess?

cheers

Steve

Hi Steve,

Thanks for the scene file! I just saw it. Very useful!

Please have a look at the file below. The Text Plane (again I used a proxy here: Alpha>Checkerboard, as in your example as well) has a Compositing Tag. Inside of this tag you have the option to exclude the object from AO calculations.

Scene file 02
https://www.amazon.com/clouddrive/share/RwNOLAGWwiwEK9b63esvbiEp86zYWzn67JWq7Hsy1UT

In the Render-Settings, I have set the AO to evaluate Transparency. Which might not be needed in this case, but I wanted to mention it. I get a clean Object Buffer in your scene with just the Compositing Tag settings.

Here is a short run-down of the options: (one minute screen capture)
https://www.amazon.com/clouddrive/share/FDYZESmpjNLCEfdemPjEZuUghBieAnps1fUTy5I3QfD

All the best

Hi there

I found out what the problem was with the Ambient Occlusion. Turns out I had to flip the normals on the polygons. I’m guessing that the inside was towards the top and making AO render them black. Now it seems to be working the way it should.

I’ll check out you file now and try it with the rendersettings you mentioned.

Thanks once again!

Steve

Thanks for the additional information, Steve.

Edit: Please check your file without AO and perhaps for reference in Standard render. Have a look at how the materials are matching, text and paper.

I haven’t really checked your file, as I got a warning about a missing plugin;  E.g., I see an intersection of the geometry. The normal direction has an influence on the Displacer. Based on the 3rd party parts: I used my own example.

My suggestion, use the Compositing tag, as it excludes the Text plane from the AO calculation (if checked) and that is the best way to deal with it. /edit

Cheers.

Edited

P.S.: Steve, I have checked your input from above, and I can’t confirm the findings. As usual, I have to do it practically, as a scene file works or it doesn’t. This is easily shown with a short screen-capture. I color the text page temporarily with a different color for demo reasons, which is just to create better readability between the paper-page and the text-page.
I have ignored the alert about the missing plugin, I assume it delivers just the information for the Bend parameter. Let me know if that is wrong.
I hope the Reverse Normal demo shows that this wasn’t the cause. Anyway, AO works with Normals, as a normal map can demonstrate easily. But the geometry is key of course.

This afternoon I checked this practically.  Still, I check everything in scene file form, as things might change and I don’t like to answer from memory. I edited my post above, as I had, in fact, replied without directly checking it in Cinema 4D directly. Since you saw it working, I thought fine …, but it was nagging on me, something was not sitting right. What showed up as a solved problem was, in fact, a result of your change, but it pushed the polygon below the other. Not visible any longer, hence no problem anymore.

So here is the screen capture and I hope that chapter is cleared now. (1min)
https://www.amazon.com/clouddrive/share/4GNs5K0xIpybU7ykoBAfDl2XLoxJiUIY2hDCNIYGkLD

As a side note: The AO is a “geo-mechanical” effect, not anything based on the light-emission of any source whatsoever. I know that people love to use it.  Personally, I love AO if it is calculated on GI, etc. the fake one, not so much. It needs to be handled with great care to work positively.

ENJOY