Black Eyes in iRay

karl

[Firstly, forgive the grainy quality of these images! My PC is old so DS switches to CPU rendering. As such iRay preview doesn't really work, and I preview by doing a render, then stopping it after 5 mins when I have an idea of how it looks. So these images are all just a few iterations, but I didn't want to wait hours just to have clearer images to make a point. Okay, preamble over!]

Last night I was doing a character render, and thought the eyes looked weird. I zoomed in and cropped. That's image 1. The black eyes made me think I may have applied some alien or robot eyes by accident to the character, so I'd need to change them and redo everything. But I did a bit or reading and realised it is a known issue, so decided to follow the instructions and see what helped. By the way, my Render Settings: Optimization -> Max Path Length was on the default of -1, so it isn't related to that.

Image 2 is where I zoomed in and made the light a bit brighter so I could then try different things. Yep, definitely black in the eyes.

For image 3 I changed a single setting:

Optimization>Instancing Optimization
I set it to Speed, rather than Auto. Apparently it helps with characters far from the environment centre, cuts back on black eyes known bug.

It is better, but not perfect. The black has receded, and rather than looking demonic he now just has a black ring in his eyes. At a distance it might not even be noticeable. Or I could maybe fix it in post. Still, it's annoying if you are trying to get an image just right.

Having read other pages I was pretty sure the issue was caused by my character being some distance from the starting point. So I parented everything to the character, then in the Parameters tab reset all the coordinates to 0,0,0 so that he is back in the centre (along with the world around him, lights, camera, corridor, so hopefully everything is still in the right place). That fixed it, as you can see in image 4.

Apparently if the character is far from the centre where Daz starts, then a bug in iRay means the whites of their eyes can end up black. In this case it was a big scene I set up with planet and spaceship, then I moved the character to the right place in the scene. I never realised this bug existed. An extra complication to deal with! Especially as it occurs due to normal use of the DS scenes. Still, I understand it now. Thought I'd share it with you in case you ever run into it in close ups! It's handy to have examples of what the problem is, and how different attempts to fix it affect the final image (someone else could do this with nicely rendered eyes for better examples).

I got the help did a lot of reading and watching to try and work this out, so these are worth looking at if you run into this issue:

https://www.daz3d.com/forums/discussion/65991/black-eyes

https://forum.daz3d.com/forums/discussion/496016/black-eyes-location-problem-current-state-of-things

https://forum.daz3d.com/forums/discussion/188721/sclera-black-in-iray

https://www.renderosity.com/rr/mod/forumpro/?thread_id=2918517

Happy rendering!

margrave

Having read other pages I was pretty sure the issue was caused by my character being some distance from the starting point. So I parented everything to the character, then in the Parameters tab reset all the coordinates to 0,0,0 so that he is back in the centre (along with the world around him, lights, camera, corridor, so hopefully everything is still in the right place). That fixed it, as you can see in image 4.

Doing this is pointless, because Iray already centers everything when you change the Instance Optimization. If Speed doesn't solve it, then Memory should, and vice versa.

karl

margrave said:

Doing this is pointless, because Iray already centers everything when you change the Instance Optimization. If Speed doesn't solve it, then Memory should, and vice versa.

Interesting, none of the other guides I read suggested that. So changing Optimization>Instancing Optimization sets everything to 0,0,0? If so, why do we need to change that obscure setting, why doesn't iRay just do 0,0,0 anyway? Regardless, if I change it to Speed then back to Auto, it would be the same as parenting items and changing the parameters to 0,0,0?

As a test I gave it a go.

The default Auto = problem black eyes.

Changing it to Speed was better, but left black rings. (So isn't as good as the parenting/0,0,0 fix.)

Changing it to Memory seemed to fix it, and gave the same result as the parenting/0,0,0 fix, but a lot easier.

Which begs the question, why isn't this setting, which seems really important, discussed more? The Daz help guides I saw didn't seem to cover it, and third party guides either skip over it, or recommend choosing Speed, but this suggests that for me I should always choose Memory. It seems like an important piece of advice for people on low-power systems!

Anyway, thanks for the suggestion. Are there any negative implications to me always setting that as Memory?

margrave

Memory and Speed are very misleading. "Memory" means instancing is enabled, which saves memory. "Speed" means instancing is disabled, which is faster. Disabling instancing means every instance in a scene will get its own copy of the geometry. If you have a scene with 8192 grass instances, your computer will probably burst into flames.

So, if you know a scene doesn't have any instances, you can get a slight speed boost with Speed. Otherwise, set it to Memory.

Here's a thread I made citing the specific part of the Iray docs that discuss the issue:

https://www.daz3d.com/forums/discussion/506431/the-black-eyes-bug-explained

karl

Really interesting and useful, many thanks. I'll use the "Memory" option by default in future. I did an all-night render for a book cover last night using that setting (attached), and the eyes were fine.

One thing I am unclear on - if setting it to Speed or Memory reset the camera to 0,0,0, why doesn't the default of Auto do the same thing? (Presumably Auto picks whichever seems most relevant?)

margrave

karl said:

Really interesting and useful, many thanks. I'll use the "Memory" option by default in future. I did an all-night render for a book cover last night using that setting (attached), and the eyes were fine.

One thing I am unclear on - if setting it to Speed or Memory reset the camera to 0,0,0, why doesn't the default of Auto do the same thing? (Presumably Auto picks whichever seems most relevant?)

Not sure. I think there's a bug in Daz's implementation. Somebody else speculated that the mere act of changing the Instance Optimization forces Iray to recenter the scene, rather than what it's set to, but I don't know for sure.