Ground Projection: Corona vs. V-Ray

[JonasNöll]

Hi, I tried the Corona Demo recently and must say that I'm quite impressed on how easy certain basic tasks work.

Especially I can not achieve a correct or nice looking ground projection with V-Ray. The environment always looks distorted and warped while in Corona it looks pretty natural. Of course there are artifacts, but overall mapping the HDRI looks quite convincing in 95% of the cases while in V-Ray it looks in 99% of cased distorted and warped. Is there anything that I am missing? Corona has an additional parameter for the camera height which are not present in V-Ray.
Same issues with the OSL-HDRI-Env for 3dsMax 2021 but afaik the code is the same as in V-Ray.

Any idea on how to improve this or am I doing something wrong? In Corona it's pretty nice to try out different HDRIs with your model but in V-Ray it's always a so distorted and unnatural that it requires the use of backplates.
Thx

[nikoleta.garkova]

I did a (very) simple scene to compare, doesn't seem to produce any differences in regards to distortion in either case. Would you be able to attach the tests you did here or send them over to support@chaogroup.com so we can better see the settings used in both scenarios? Thanks.

[JonasNöll]

Hi, thank you, I will mail them over in a second!

[JonasNöll]

Btw. any reason why you zoomed in 200% in the Corona rendering and had to crop camera view in order to get the same picture like in V-Ray? Shouldn't they be 640*480 px and 1:1 with no Zooming/Cropping to compare?

Edit: Nevermind, you seemed also to crop into the V-Ray rendering 200% Do they look the same if you don't crop into the center but show the whole camera view? If I would crop my sample pictures in the center then they would also look comparable. Could you pls post the whole camera picture?

[nikoleta.garkova]

Hi Jonas, there you go: 1086005.zip

[JonasNöll]

Hi, thank you!
Interesting they match exactly. I sent you my scene. I can't get the same effect for both with V-Ray always being distorted.

V-Ray worklow: Creat Domelight -> VrayBitmap in Domelight -> Set to Spherical -> Enable Ground Projection -> Play with Radius
Corona workflow: Corona Bitmap in Env -> Set to Dome -> Play with Radius and Camera height

Anything that you are doing differently from me?
Thx

[Yuhgelin]

I also must be missing something because I have never had this working as expected....very curious to know why not.

[JonasNöll]

I also must be missing something because I have never had this working as expected....very curious to know why not.

Yes, let's hope there will be an update on this

[kosso_olli]

V-Ray worklow: Creat Domelight -> VrayBitmap in Domelight -> Set to Spherical -> Enable Ground Projection -> Play with Radius

There hardly is any room to play with the radius parameter: This has to be close to the height of the camera center taking the HDRi (camera plus tripod). For our capturing device, this is something between 100cm and 120cm. Apart from that, there is not much you can do in regards of projection, except for shifting the center using the coordinates.
I requested some more options more then three years ago and regularly bumped the topic, but I never heard anything of it. For us, a simple size multiplier would be more than welcome.

https://forums.chaosgroup.com/forum/...rrectly-scaled

[JonasNöll]

Oh good, so I'm not the only one with this issue. Thanks for the link, that's exactly the same issue that I am facing. It's just frustrating because Corona seems to handle it so much better without any weird distortions and for some shots it's absolutely enough to use the HDRI in the environment and the model is looking like really being placed in the environment. In V-Ray it is always a so crazy distorted that its basically not usable for anything. Corona has the camera height as an option, so probably this is doing the trick.
It is very strange that nikoleta.garkova can get an identical look and I am hoping that she can share her settings or examine my scene or let me know if there is something that I am doing wrong or if this behavior is expected

[nikoleta.garkova]

Hi all, and thanks JonasNöll for providing the files - I am testing your scenes and will let you know shortly, looks like we will need to do some improvements on the Ground projection options though. Thanks for the patience.

[kosso_olli]

It is very strange that nikoleta.garkova can get an identical look and I am hoping that she can share her settings or examine my scene or let me know if there is something that I am doing wrong or if this behavior is expected

It also depends a lot on the environment. It is working very good with large open spaces (parking lots, helipads etc.) in V-Ray, too. But Corona and Vred both have additional features to make it work in other scenarios.

[nikoleta.garkova]

Thanks all for the input. After going through the scene and settings that Jonas sent - there is, indeed, a difference in the distortion levels. I've logged an improvement request in our internal system (number ID: VMAX-10347) for devs analysis.

[JonasNöll]

Alrighty, great so see that it will be worked on! Thx!

[vlado]

V-Ray tries to preserve the way the dome light looks above the horizon so that the illumination doesn't change; it is still infinitely far away and doesn't have an actual radius. This is different from Corona where the dome light becomes actually a hemi-spherical light.

Best regards,
Vlado