Antialiasing Issue for progressive vs bucket

[wessam]

Hi,
on GPU RTX
when I compare progressive vs bucket renders it is visible that the edges are not correct for the progressive method, and it is more visible when I render selected objects and try to compose the render over and existing image, this was happening for years on different workstations and I finally decided to ask
please advice.

[Muhammed_Hamed]

Hey Wessam,

Progressive is the recommended way to use V-Ray GPU, on a simple scene I cannot reproduce the antialising issue you mentioned
Do you have a screenshot or scene? we need to reproduce this on our end

Best,
Muhammed

[Joelaff]

I wonder if the OP is referring to the rough edges often seen (esp with progressive) on renders with Render Mask set. ??

[wessam]

@Joelaff

I wonder if the OP is referring to the rough edges often seen (esp with progressive) on renders with Render Mask set. ??

yes, exactly

[Joelaff]

Not sure if there is a way to avoid. I usually don’t use progressive. In fact, I hardly use progressive for anything.

It does put a warning in the log (with some interesting spelling):

Warning : Render subsets and progressive sampling lead to artefacts along object edges.
​

[Joelaff]

You can make a matte in post (from a previous render’s alpha perhaps) and expand the matte to render more than you need, then shrink and feather it when you composite. That is what I have done when I needed to render individual objects. But normally we just end up re-rendering the entire frame.

[fixeighted]

@Joelaff

Not sure if there is a way to avoid. I usually don’t use progressive. In fact, I hardly use progressive for anything.

It does put a warning in the log (with some interesting spelling):

Warning : Render subsets and progressive sampling lead to artefacts along object edges.
​

Did you mean in the spelling of ‘artefacts’ ?

That’s totally fine, as it’s just the UK version.

It’s the ‘lead’ that is incorrect, as it should be ‘leads’.

Just saying

[Joelaff]

Chiefly British :o I did not recognize that was one of the British Flavours.

Given the subject is plural I would say “lead” is correct, rather than “leads.”

EDIT: But I suppose the meaning implies, “Render subsets with progressive sampling leads to artefacts along object edges,” which would indeed be singular, and make “leads” correct, as well as be more clear.

EDIT REDUX: What the heck am I talking about? “Subsets” is still plural either way. So “lead” it is. Carry on.

[wessam]

@Joelaff

You can make a matte in post (from a previous render’s alpha perhaps) and expand the matte to render more than you need, then shrink and feather it when you composite. That is what I have done when I needed to render individual objects. But normally we just end up re-rendering the entire frame.

Thanks, though that’s a work around bur still not perfect, specially with high resolution renders and super picky clients

[wessam]

@Muhammed_Hamed

Hey Wessam,

Progressive is the recommended way to use V-Ray GPU, on a simple scene I cannot reproduce the antialising issue you mentioned
Do you have a screenshot or scene? we need to reproduce this on our end

Best,
Muhammed

Thanks, tbh it’s amazing how it is in the log like the previous post, and you guys are not able to reproduce. The issue been there for years, I want to help you with the investigation but I am on a tight deadline currently.

[fixeighted]

@Joelaff

Chiefly British :o I did not recognize that was one of the British Flavours.

Given the subject is plural I would say “lead” is correct, rather than “leads.”

EDIT: But I suppose the meaning implies, “Render subsets with progressive sampling leads to artefacts along object edges,” which would indeed be singular, and make “leads” correct, as well as be more clear.

EDIT REDUX: What the heck am I talking about? “Subsets” is still plural either way. So “lead” it is. Carry on.

I thought that ‘render subsets’ was the parameter/option label, so singular, but apparently not.

Given the statement implies that the two things, used together, produce artefacts, then leads is still correct I think, instictively (I’ll check with my tame linguist later), but a simple
solution would be to use ‘will lead to’ or a variation thereof

I do love a bit of pedantry in the morning

Sorry OP…didn’t mean to hijack

[wessam]

@Muhammed_Hamed ​
please check the screenshots attached,
Again the issue is worst when making a masked render, (like render selected)

[wessam]

Hi,
this remains a significant issue that needs to be fixed guys! it is amazing to be aware of an issue and it can easily be reproduced.

at the same time throughout your ecosystem, you always recommend progressive render like for cloud render, and yes, it is better and faster than bucket in most cases if not all.

[wessam]

a sample scene to check that reproduce the issue
https://drive.google.com/drive/folders/16RCSr-DWi8eI6lF\_n0kLTm-JrP\_zeCU\_?usp=sharing

[Muhammed_Hamed]

We will see what could be done about this ASAP
For now we have been busy with V-Ray 7, I will get back to you shortly

Best,
Muhammed

[Joelaff]

Keep in mind that rendering selected objects is never going to be technically correct, as you will be comping it on top of an existing copy of the object. So the edges will get more dense. Ideally you render the separate elements separately such that they can be comped over in post. Then it’s OK to replace the “layer.”

It’s like a colorist trying to color already comped footage by using masks. It will never be correct. It may look acceptable, but it is not the technically correct way to do things, as it produces incorrect edges. It leads to fake looking comps with bad edges, and even though it’s the colorist messing it up the VFX artists get blamed :o

[wessam]

@Joelaff

Keep in mind that rendering selected objects is never going to be technically correct, as you will be comping it on top of an existing copy of the object. So the edges will get more dense. Ideally you render the separate elements separately such that they can be comped over in post. Then it’s OK to replace the “layer.”

It like a colorist trying to color already comped footage by using masks. It will never be correct. It may look acceptable, but it is not the technically correct way to do things, as it produces incorrect edges. It leads to fake looking comps with bad edges, and even though it’s the colorist messing it up the VFX artists get blamed :o

Thanks, but I have several different scenarios where rendering selected object are perfectly technically correct.

[wessam]

@Muhammed_Hamed

We will see what could be done about this ASAP
For now we have been busy with V-Ray 7, I will get back to you shortly

Best,
Muhammed

Thanks Muhammed,
releasing V-Ray 7 makes it more important to be shipped fixed. waiting your feedback.

[Joelaff]

@wessam

Thanks, but I have several different scenarios where rendering selected object are perfectly technically correct.

I am interested in hearing more? Do you have them on alpha and then comp them over a clean BG? In that case, sure.

My point is that if you have your plants rendered already on top of some background all in one image, and then you select them and render them with a render mask-- then when you comp them over an already combined image you will get double edges, which is not correct. Of course if you break stuff into layers then it works fine. We do that with scene states, though, rather than render masks.