shadow color/transparency

monson67 · September 29, 2016, 06:44:46 AM

Regarding the shadows looking like they have JPG artifacts (I know they're not - I get what you meant), I've experienced this as well. Though, it's difficult to know if you and I are talking about the same thing without seeing examples of what you're dealing with.

Anyhow, I'm still very new to KeyShot, but I think that my problem was that my objects were intersecting with the ground plane. When I moved them up so that they were just barely hovering above the ground plane, that seemed to help. Then again, I was rendering shadows separately from the actual object using the emissive material trick, so the artifacting may have only been in areas that were going to be covered up by the object later on in Photoshop. I can't remember for sure. Either way, it's something you may want to try.

Rex · September 29, 2016, 09:27:28 AM

Yes, would be good to see an example of the shadow artifacting you are experiencing.

andy.engelkemier · September 29, 2016, 10:30:42 AM

So I've tried every combination I could think of in my current file. Quality 1, Quality 5, no sharp shadows, low/high quality GI, Lower/Higher Samples.
I can't get this to happen in the file I'm working on today. I'm Pretty sure that I also can't get this to go away when I get it, trying the same things, and even using a ground plane instead of shadows.
So I will take extra care next time I get it. It's looking more like an error now since I am unable to repeat it. I have since updated that file, and it renders fine.

I've blanked out the product. I didn't render it as an emissive material or anything. I just masked it off in photoshop because I shouldn't be sharing that product. I figured the silhouette of just the caster area is probably fine though.
I just realized also that I May have been trying to save some time and rendered it out on black. I don't have time to try any more experiments though. So I'm wondering if it's only sampling RGB and not sampling alpha, which would be a nice option if that's what's happening.
Switching your background to black eliminates "glowing" shadows.

Rex · October 04, 2016, 10:00:44 AM

Hey Andy,

Are you using Advanced Control render output? Try unchecking "Global Illumination Cache" next time this comes up.

Thanks

andy.engelkemier · October 04, 2016, 10:18:13 AM

You might be on to something. I haven't had it since, so it's very likely that it's somehow cache related. I'll come back to this if it comes back and post results.

Speedster · October 04, 2016, 03:23:17 PM

If you are rendering out to a TIFF or .png with alpha checked, always use a black background. This avoids "white stuff" from coming through your shadows. This may not be the issue you are having, but it's a good trick to remember.
Bill G

andy.engelkemier · October 13, 2016, 01:15:06 PM

Huzzah! I figured it out.
A small portion of the model was under the ground plane by Just a hair. I moved it up .0237 (then I rounded up to .025) and it was fine.

The odd thing though, the first few "frames" of it clearing up looked fine. Then after a few seconds those areas just look terrible, and stay that way.
Once I moved it all above the ground plane it was fine.

So I guess just make sure none of your model is below ground plane.

monson67 · October 13, 2016, 01:42:44 PM

Quote from: monson67 on September 29, 2016, 06:44:46 AM
...I think that my problem was that my objects were intersecting with the ground plane. When I moved them up so that they were just barely hovering above the ground plane, that seemed to help.

andy.engelkemier · October 13, 2016, 02:12:01 PM

Yes, I know you mentioned that. It was modeled above in rhino. So it must just be a tolerance issue or something. .037 shouldn't be an issue.
I misread your post the first time also. I was thinking you were talking about a coinciding issue. The artifacts have nothing to do with the part of the model that went through the ground plane. It's just that a part goes through at all. That's what surprised me.
So bad news if you have a power chord going straight down or something like that.

Rex · October 19, 2016, 11:16:18 AM

Hi Andy,

Actually the issue is related to poor aliasing when using advanced control render output mode. You can either increase the anti aliasing value or use maximum samples.

andy.engelkemier · October 19, 2016, 11:27:31 AM

That could be, but I'm not so certain that it's only related to that.
In the viewport, it looks fine for a few seconds. Once it clears up a bit, the "artifacts" suddenly pop up. I hadn't pulled up the heads up display to see if it's always the same number of frames, but I have a feeling it is.
So it happens in both real-time And the advanced render mode.