There seems to be a bug with shadow rendering and distances from origin

[Invertex]

Depending on subtool distance from origin it greatly affects shadow rendering for all subtools in the scene, not just the one far from origin. Even just having a sphere 10 units away from origin and your main model will result in the shadow rendering creating weird streaking on the model where shadows aren’t really happening.

Simple way to reproduce this, load the DemoHead.ZPR, do a render, shadows look clean.
Append a sphere, move it up 10 units. Render the head again, a bunch of weird surface streaking starts to happen in the lit areas. Deleting the sphere allows it to render properly again.

Example, DemoHead rendered all default settings:

Now rendered again with sphere appended and moved up around 10 units.

Increasing rays drastically has seemingly no effect on it either.

[Spyndel]

Assuming BPR render because of tag, but there are two different shadow rendering engines inside of ZB, so be very specific when describing steps. Cant duplicate scenario exactly, but try adjusting the Render > BPR shadow> Angle. Lower values create a solid, crisp shadow…higher values create fragmented shadow of the type on display in your example. Higher values require increased levels of Render> BPR shadow > Blur to look natural. Rays also important, but costly in performance. Find suitable balance between all values.

[Invertex]

Assuming BPR render because of tag, but there are two different shadow rendering engines inside of ZB, so be very specific when describing steps. Cant duplicate scenario exactly, but try adjusting the Render > BPR shadow> Angle. Lower values create a solid, crisp shadow…higher values create fragmented shadow of the type on display in your example. Higher values require increased levels of Render> BPR shadow > Blur to look natural. Rays also important, but costly in performance. Find suitable balance between all values.

Yes, hitting the BPR button, not touching any settings. Load up the DemoHead project, append regular ZBrush polysphere, and move that sphere up until you hit a value of -10 below your manipulator. Then hit the BPR render button.

This isn’t an increased angle issue, I didn’t mention any change to default settings, and default settings are an angle of 0.

[Spyndel]

I’m sorry. Your instructions do not allow me to replicate the issue. Moving an appended polyshpere with gizmo to -10 units above the demohead results in a sphere very far above the demohead, and not useful for rendering evaluation. Either I’m misunderstanding what you say, or there’s another variable in play.

[Invertex]

I’m sorry. Your instructions do not allow me to replicate the issue. Moving an appended polyshpere with gizmo to -10 units above the demohead results in a sphere very far above the demohead, and not useful for rendering evaluation. Either I’m misunderstanding what you say, or there’s another variable in play.

I gave example images with a description when I made this post. You render the head again like in the second image example I gave, which is the situation after moving the sphere up, and rendering the head…

This isn’t just a personal issue, this is an issue I was helping a friend with trying to determine why their shadows were screwing up in their render, even after importing just a clean OBJ of their model. After much playing around with and comparing settings it had turned out the issue was simply the model being 10-20 units higher than ZBrush scene origin, resulting in terrible surface artifacts from the shadow pass (this isn’t about the actual dark shadowed areas at all, nor the crispness of it). You can do this instead of appending the sphere too, just move the DemoHead up by 15 units or more and get a fairly zoomed in view like in my screenshot, then do a BPR render. You will notice weird painterly lines appearing all over the mesh like in my final image.

[Spyndel]

As you like. “Weirdly painterly shadows” are pretty common in Zbrush rendering. It’s only a bug if it behaved differently in previous version under the same scenario. Ill say again, increase blur settings, and/or tweak shadow angle.

Sorry I couldn’t be more help, and good luck.

[nebular]

isn’t the 2nd render not BPR only Best render?

[Invertex]

isn’t the 2nd render not BPR only Best render?

Nope, hit BPR button each time, literally only difference in second screenshot is that I moved a sphere in the scene 10 units above that head, absolutely nothing else touched.

I’ve been using ZBrush for over a decade now and never really encountered this issue much until a friend just ran into it, took quite a bit of troubleshooting to finally figure out it was something so weird and simple as this.

As you like. “Weirdly painterly shadows” are pretty common in Zbrush rendering. It’s only a bug if it behaved differently in previous version under the same scenario. Ill say again, increase blur settings, and/or tweak shadow angle.

Sorry I couldn’t be more help, and good luck.

I’m quite aware ZBrush has its quirks and I love it regardless, but I’m not talking about “weirdly painterly shadows” in the sense you seem to be implying, like I said, ignore the actual shadowed areas… look at the bright areas of the mesh, compare those bright areas to the first image.
This seems like fixable behavior that I believe should be brought attention to. Just because the issue has been around for multiple versions (I confirmed this in 4R8 as well just now), does not mean something is not a bug, just an unfixed bug. Thus my posting of this thread was less about “how to work around it” feedback and more so hopes of getting developer word on this as to whether it’s on their radar of things to potentially improve/fix or not, as this is clearly a fault in the raytracing approach/setup used by the shadow pass.

[nebular]

I tried to recreate it but I didn’t found any issues. The bpr alwyas seem right for me.

[Nicolas_Marin]

i have the same problem

you found any solution for this bug >?

[zaidoigres]

Hi, I know it’s an old thread but this was driving me nuts and the post by INVERTEX helped me out. So, maybe this image will help clarify the issue. You can reproduce it on a fresh new session, just by loading up the demohead tool and moving it far away from the scene origin, then zooming in and doing a BPR render.