Community
Arnold for Cinema 4D Forum
Rendering with Arnold in CINEMA 4D using the C4DtoA plug-in.
cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

Shadow Matte question - grainy Shadow Mask AOV

5 REPLIES 5
Reply
Message 1 of 6
peter.fagerberg
661 Views, 5 Replies

Shadow Matte question - grainy Shadow Mask AOV

I was wondering if someone could point me to what parameter(s) I need to crank in order to get a decent Shadow Mask AOV with less grain? If I increase the number of light samples the mask just gets brighter but it is still very grainy.

Here's are some images illustrating my problem. The standard alpha looks OK but the Shadow Mask AOV is pretty much useless. What am I missing?

render.jpg

alpha.jpg

shadowmask-aov.jpg

Labels (3)
5 REPLIES 5
Message 2 of 6

How many light samples are you using? You could also try increasing Camera (AA) samples.

Lee Griggs
Arnold rendering specialist
AUTODESK
Message 3 of 6

Update: I think I fixed the grainy problem! There's a filter setting in the AOV and mine was set to Default. However, once I fiddled with it, the setting somehow "reset" and now the graininess is gone! Somehow, it must have become corrupted. It's now at Default and working.

But the problem with the number of light samples and the mask's "exposure" persists. As I increase the number of samples the mask becomes more and more exposed until it is totally washed out. I enclose images with 1 and 5 light samples respectively. Strange isn't it? Shouldn't just quality improve?

1 light sample

samples-eq-1.jpg


5 light samples

samples-eq-5.jpg

Message 4 of 6

There are two different AOVs: shadow_matte and shadow_mask.

shadow_matte is a greyscale AOV containing shadow intensity and it has a gaussian filter applied by default. I think what you need for compositing is this one!

shadow_mask is a float AOV which shows which pixels have any shadow. So it's 1 where shadow_matte > 0, and 0 otherwise. By default is has a closes filter applied, that's why you see it grainy. The result when increasing light samples is expected here because the render is more detailed.

Hope this makes sense.

Message 5 of 6

OMG, you're absolutely right! I got my AOVs mixed up - sorry about that! The Shadow Matte doc had me all confused... To summarize, the use case for the two primary shadow AOVs which can be used for shadow manipulation in post is as follows?

  • The Shadow AOV is only used together with the Shadow Matte shader. It creates a shadow mask for the shadows on the shadow matt object (e.g. a ground object), ideal for adding these specific shadows in post. Also, very useful if your final comp has to contain an alpha channel, e.g. a masked floating object where you still want the shadows.
  • The Shadow Matte AOV really has nothing to do with the Shadow Matte shader. It generates a mask for all the shadows existing in a scene, irrespective if you're using the Shadow Matte shader or not. It's can be used to tweak overall shadows in post.

Hope I got that right! Please set me straight if I'm still mixed up.

Message 6 of 6

Yes, that's right.

Can't find what you're looking for? Ask the community or share your knowledge.

Post to forums  

Autodesk Design & Make Report