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?
How many light samples are you using? You could also try increasing Camera (AA) samples.
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
5 light samples
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.
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?
Hope I got that right! Please set me straight if I'm still mixed up.