question

Peter Fagerberg avatar image
Peter Fagerberg asked

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

c4dtoaaovshadow matte
render.jpg (145.5 KiB)
alpha.jpg (62.6 KiB)
shadowmask-aov.jpg (231.2 KiB)
10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Lee Griggs avatar image
Lee Griggs answered

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

10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Peter Fagerberg avatar image
Peter Fagerberg answered

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


samples-eq-1.jpg (109.4 KiB)
samples-eq-5.jpg (43.8 KiB)
10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Peter Horvath avatar image
Peter Horvath answered

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.

10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Peter Fagerberg avatar image
Peter Fagerberg answered

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.

1 comment
10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Yes, that's right.

0 Likes 0 ·

Write an Answer

Hint: Notify or tag a user in this post by typing @username.

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Welcome to the Arnold Answers community.

This is the place for Arnold renderer users everywhere to ask and answer rendering questions, and share knowledge about using Arnold, Arnold plugins, workflows and developing tools with Arnold.

If you are a new user to Arnold Answers, please first check out our FAQ and User Guide for more information.

When posting questions, please be sure to select the appropriate Space for your Arnold plugin and include the plugin version you are using.

Please include images, scene and log files whenever possible as this helps the community answer your questions.

Instructions for generating full verbosity log files are available for MtoA, MaxtoA, C4DtoA, HtoA, KtoA, and Kick.

If you are looking for Arnold Documentation and Support please visit the Arnold Support site.

To try Arnold please visit the Arnold Trial page.

Bottom No panel present for this section.