render settings overscan no being applied to multi channel EXR

[seandunderdale]

I have a beauty that renders fine with overscan turned on with 10% dded on equal margins. I render these as png and everything is fine. I render a utility pass which has cryptomatte etc as a multi channel exr and it does not render with overscan added.

V-Ray 5 for Maya, update 2.2 (v5.20.02, revision 31195 from Jan 7 2022) and Maya 2022.3

[hermit.crab]

That nightly build was removed (most likely unstable). It seems to work fine in the latest one.

[seandunderdale]

ok cool. Good to know.

[seandunderdale]

Im using V-Ray 6 for Maya, update 1

(v6.10.00, revision 32127 from Jun 10 2023) in Maya 2023.3 and this is still a problem. I use overscan with EXR and its ignored.

Attached files...one is the render with 100% overscan in VFB. The other is the saved file opened in PS. As stated before, overscan works when I render to PNG, but not to EXR.

[SonyBoy]

This may not be the issue, but overscanned pixels are ignored by some applications including (as I recall) Photoshop. After Effects reads them but gives no indication they are there, while Nuke will give you a bounding box to indicate they're present. I was very confused by this at first, but kinda makes sense for compositing purposes (which is normally why you render overscan).

[seandunderdale]

I wasnt getting the extra pixels visible in Nuke or Photoshop. I cant imagine why overscan pixels should be treated any different to the normal rendererd area pixels?...but this also doesnt explain why PNG works fine, and EXR does not....in my tests anyway. If PNG overscan pixels work in photoshop and Nuke, what is happening to the EXR?

You are right about the bounding box in Nuke, but I need the extra rendered bleed in my actual render. Extra bounding box is of no use to me.

[SonyBoy]

I thought the same thing at first, but it does make sense to have the base resolution encoded correctly into the image this way, with the overscan being treated as "extra" around the edges. This way when a comper drops in a sequence, it will be correctly aligned with the original framing/composition. I assume what you're doing is something different and you want those pixels to be included in the base resolution. Unfortunately that's not how Vray handles it. However, the pixels should be there so I'm not sure about the PNG versus EXR thing. I would try batch rendering instead of using the VFB -- I seem to recall running into problems trying to do it that way, but it was a while ago.

[SonyBoy]

Also, I assume you are using the overscan settings in the camera override of the render settings to do this? There is a hack that can be used instead by setting an attr. on the camera to a value other than 1 (so, e.g. if you want overscan of 10 percent you'd set it to 1.1). Unfortunately I can't recall which attribute it is (perhaps camera scale... on the shape node, not the transform) but I know this can work, and more than likely the image will be interpreted at full rez by other programs.

[SonyBoy]

* This won't work if you're using a Vray physical camera.

[hermit.crab]

I wasnt getting the extra pixels visible in Nuke or Photoshop. I cant imagine why overscan pixels should be treated any different to the normal rendererd area pixels?...but this also doesnt explain why PNG works fine, and EXR does not....in my tests anyway. If PNG overscan pixels work in photoshop and Nuke, what is happening to the EXR?

You are right about the bounding box in Nuke, but I need the extra rendered bleed in my actual render. Extra bounding box is of no use to me.

Not sure how you're opening the .exr in PS, but if you're using the EXR-IO plugin, prior to opening you should tick the "Ignore display window" option to see the overscan.

[seandunderdale]

cool! ok that fixes photoshop. Do you know how to do the same for Nuke? Also, how come these pixels get treated any differently anyway?

[seandunderdale]

Also, I assume you are using the overscan settings in the camera override of the render settings to do this? There is a hack that can be used instead by setting an attr. on the camera to a value other than 1 (so, e.g. if you want overscan of 10 percent you'd set it to 1.1). Unfortunately I can't recall which attribute it is (perhaps camera scale... on the shape node, not the transform) but I know this can work, and more than likely the image will be interpreted at full rez by other programs.

This is how I used to do my overscans / add render bleed, but it adds it uniformly on all sides. the beauty of the Vray solution was, we would ALWAYS get a client comment late in the project that they would "love to see 20% extra on the left" or they need 15% top and bottom. We dont want to change the camera, we dont want to touch the camera or its settings...it was signed off months ago, and handing over with camera offsets confuses artists who pick up a freelancers shot from the year before. The Vray overscan allows total control to add bleed in the way the client understands, so its perfect. I just couldnt work out why it was working for PNG and not EXR.

Now it seems we have a fix for EXR in PS. I did have EXR-IO installed, just hadnt played with any settings in this case. I can see the bounding box in Nuke has changed, so clearly there is some data being shown, I just need to get that to appear in the viewer.

Also, I have tested both batch rendering and VFB rendering. (not manually saving exrs from VFB which wont do for animations) Both of my tests have PNG working out of the box, and EXR not.

[hermit.crab]

cool! ok that fixes photoshop. Do you know how to do the same for Nuke?

Right-click in the Viewer's black space and check the "Show overscan" option.

Also, how come these pixels get treated any differently anyway?

Not sure what you mean here, but usually the overscan is used to resolve issues with post-processing effects on the edges (such as motion blur), where you need information beyond the frame to get correct results. Otherwise, in .exr, overscan bbox is written as metadata, while in .pngs the resolution is directly added.

[seandunderdale]

ok that clears it up, thankyou. I feel like your last post should be added to the help docs, if that info isnt there. I couldnt see anything...

"Also, how come these pixels get treated any differently anyway?"

What I meant was, and you do address it in your post, is overscan rendered pixels are treated differently, or theyre tagged differently, both by Vray and by compositing apps, so when you bring them in, they dont get read as part of the main render, unless you do an extra step (tick boxes in EXR-IO f.e). I did not know this, so was confused why they didnt automatically show up in the EXR beauty, but do in a PNG. When something behaves like that, it comes across as a bug.