Is DAZ addressing the Black Sclera when character is far from world origin issue?

RL_Media

Octane, you can also fix the issue in most cases, by adding more zeros to ray epsilon, making it smaller, until it goes away. Or at least that worked back when I was trying out the plugin.

Son of the Raven

Not specifically about the sclera in this shot, but does the problem here come from the same basic reason for the sclera issues, and geoshell issues when away from world center? It might also be worth noting that in a different shot, facing a different direction, completely different pose, but very nearly the same location in the scene did not have this issue.

In this shot, I'm talking about the dark artifacts on her forehead, and there is also a bit at her bikini crotch line.

Not sure if the darkness in her mouth is also an issue or just due to shadow - I need to reload the scene and check it to see if it's an actual rendering failure or not.

 

RayDAnt

Son of the Raven said:

Not specifically about the sclera in this shot, but does the problem here come from the same basic reason for the sclera issues, and geoshell issues when away from world center? It might also be worth noting that in a different shot, facing a different direction, completely different pose, but very nearly the same location in the scene did not have this issue.

In this shot, I'm talking about the dark artifacts on her forehead, and there is also a bit at her bikini crotch line.

Not sure if the darkness in her mouth is also an issue or just due to shadow - I need to reload the scene and check it to see if it's an actual rendering failure or not.

Almost certainly it's the same thing causing the anomalies seen here (assuming you hadn't been playing with the Instancing options dropdown box while using Iray liveview after placing the figures/camera in the scene before starting the final render.) The official name (so much as there is one) for the sclera issue is "Shadow Acne", and it can technically appear on any type of object. Eyes just happen to be where it shows up most readily in typical DS/Iray use.

outrider42

A geoshell is similar to the eye setup when you think about it. Genesis has the eyeball, and just overtop the eyeball is the 'eye moisture'. This eye moisture surface is similar in function to a geoshell, as the geoshell also sits just above the Genesis mesh and often uses transparanecy.

So any situation where the black sclera can happen can effect geoshells, too. It can impact other things as well. These are just the most easily noticed issues. I did some testing and found some other things as well. I believe it was Chromatic SSS, figures that use chromatic sss may get darker as they move away from the world center. Move far enough away, and use "auto" instancing and you can get some pretty horrific results.

It can go from this

To this

This is supposed to be Sanjay 8, not the spawn of Satan. This abomination was accomplished with his default skin settings, placing him at 5000 units from the center, and using the "auto" setting for instancing.

PerttiA

Similar problems have existed for years even in professional software like AutoCad, when dealing with small changes far from world center, it may be something DAZ cannot fix, at least not without cost as increasing precision would make everything heavier.

Just move your characters closer to the world center.

RayDAnt

outrider42 said:

A geoshell is similar to the eye setup when you think about it. Genesis has the eyeball, and just overtop the eyeball is the 'eye moisture'. This eye moisture surface is similar in function to a geoshell, as the geoshell also sits just above the Genesis mesh and often uses transparanecy.

So any situation where the black sclera can happen can effect geoshells, too. It can impact other things as well. These are just the most easily noticed issues. I did some testing and found some other things as well. I believe it was Chromatic SSS, figures that use chromatic sss may get darker as they move away from the world center. Move far enough away, and use "auto" instancing and you can get some pretty horrific results.

It can go from this

To this

This is supposed to be Sanjay 8, not the spawn of Satan. This abomination was accomplished with his default skin settings, placing him at 5000 units from the center, and using the "auto" setting for instancing.

To be clear, having Instancing set to Auto or any other specific value is not what causes this. Making any change to the Instancing dropdown selection has a secondary function of triggering Iray to re-align the mathematical center of the scene (the mathematical center of the scene interally to Iray - Daz's coordinate plane values don't change throughout any of this) to whatever the current camera position is at that specific time. Thereby causing the Shadow Acne to disappear. 

 

PerttiA said:

Similar problems have existed for years even in professional software like AutoCad, when dealing with small changes far from world center, it may be something DAZ cannot fix, at least not without cost as increasing precision would make everything heavier.

 

Yeah, any 3D rendering engine reliant upon floating point numbers for making its internal calculations will run into Shadow Acne problems once you get far enough away from its (0,0,0) location in 3D space.

 

Just move your characters closer to the world center.

DS/Iray offers two ways to deal with Shadow Acne:

1. Move everything closer to world center (like you say) or,
2. Place everything including the camera where you want them, and then switch the Instancing dropdown to a different value before switching it back again (If your scene calls for an extreme camera closeup from a great distance, do the Instancing dropdown change with the camera as close to the subject as possible. Then move the camera to its intended position.)

Son of the Raven

It was on auto for me, either of the other options was a big improvement through the ira preview, but Memory looked at little better, so I'm rendering with that now.

margrave

RayDAnt said:

Almost certainly it's the same thing causing the anomalies seen here (assuming you hadn't been playing with the Instancing options dropdown box while using Iray liveview after placing the figures/camera in the scene before starting the final render.) The official name (so much as there is one) for the sclera issue is "Shadow Acne", and it can technically appear on any type of object. Eyes just happen to be where it shows up most readily in typical DS/Iray use.

The official name is "Z-fighting". As the camera travels away from world origin, Iray loses the floating point precision to sort textures that are almost-overlapping, so the distance narrows until they intersect.

RayDAnt

margrave said:

RayDAnt said:

Almost certainly it's the same thing causing the anomalies seen here (assuming you hadn't been playing with the Instancing options dropdown box while using Iray liveview after placing the figures/camera in the scene before starting the final render.) The official name (so much as there is one) for the sclera issue is "Shadow Acne", and it can technically appear on any type of object. Eyes just happen to be where it shows up most readily in typical DS/Iray use.

The official name is "Z-fighting". As the camera travels away from world origin, Iray loses the floating point precision to sort textures that are almost-overlapping, so the distance narrows until they intersect.

Z-fighting is when loss of floating point precision results in multiple closely positioned surfaces having erroneous points of overlap between them. Shadow Acne is when loss of floating point precision results in a path tracing renderer's light ray reflections getting trapped in individual surfaces (you can read about it in depth here in Chapter 6: A Fast and Robust Method for Avoiding Self-Intersection) resulting in erroneous color/brightness losses. They're both caused by the same thing and can even happen simultaneously. But the actual visual effect they have can be very different.