VRaySun Bug - System units and shadows

[Morne]

Hi all

Not sure if this is a bug or intentionally made like this:

I'm getting different results between my system units as mm and meter. For a while I've been using meter as system units, because my scenes are getting larger and larger. However I'm having issues when doing closeups of areas where there are small objects such as shrubs or grass in that they don't produce any shadows!

So I did some tests:
mm vs m system units. In both cases display units is set to mm. In both scenes, objects are the same sizes and positioned at same world coordinates.

Meter:
In this scene everything is at default. Sun shadow bias default for m is 200mm and photon emit radius is 50000mm. For my small object 3mmX3mmX200mm I get NO SHADOWS. For the bigger object the shadows are a bit fussy at the edges

Change the shadow bias to 0.2mm and I get SHADOWS, but still fussy edges


MM:
In this scene everything is at default. Sun shadow bias default for mm is 0.2mm and photon emit radius is 50mm. For my small object 3mmX3mmX200mm I get SHADOWS. For the bigger and smaller objects the shadows are crisper at the edges

Change the shadow bias to 200mm and I get NO SHADOWS, but still crisper edges


Conclusion?
The results seem similar with same settings, except for the crispness of the shadows. Why would defaults be different between m and mm and thus produce different results? Is this expected or a bug?

[GoncaloP]

Hello Morne,

My guess is that your value of 0.2mm is away to small relative to the distance from the small object and the plane of 100mm. Have you try 2mm instead? That corresponds to the value I use to work with of 0.002m and never notice anything wrong with it.

Gonçalo

[Morne]

NO I'm saying 0.2 is the "correct" default value as I get shadows with big and small objects as expected. That is 0.2mm is default for mm. BUT for some reason when your system units is m, then suddenly the default is 200mm (shifting the decimal 3 places). I think the decimal shift should NOT happen as the defaults should be same regardless of what your system units are. That way it ensures correct scale of things.

Same issue with default of stereoscopic helper. If your system units is m, then it makes the default distance between eyes 6500mm! Which makes me think of a nice pick up line:
"Wow your eyes makes me think of the stars, not so pretty, but so FAR APART!"

See what I mean? Defaults should be same physical distance no matter what system units you using. So distance between eyes should be 65mm default, not 6500mm?!

[GoncaloP]

I see what you mean...

[tashko.zashev]

Hi Morne,

Thanks for pointing this out, it's a very odd situation that we need to consider here in order to make it more comfortable.

However, basically this is not a bug in V-Ray sun and shadow bias parameter.

If bias is too high, shadows can "detach" from an object. If the bias value is too extreme in either direction, shadows might not be rendered at all.

[Morne]

Hi Morne,

Thanks for pointing this out, it's a very odd situation that we need to consider here in order to make it more comfortable.

However, basically this is not a bug in V-Ray sun and shadow bias parameter.

OK this "bug" came up again in this thread:
http://www.chaosgroup.com/forums/vbu...763#post585763

So clearly the issue needs to be adressed sooner than later I hope...

[Svetlozar Draganov]

Thank you for the feedback Morne,

Would it be possible to attach your test scene in order to investigate it ?

[Morne]

Theres nothing to investigate. Steps to reproduce is in post 1 of this thread. Display units always mm.

1. Scene units meter:
Just make a small box 5mm X 5mm and maybe 150mm high. Stick in vrayplane, vraycam, vraysun. Render

2. Scene units mm:
Just make a small box 5mm X 5mm and maybe 150mm high. Stick in vrayplane, vraycam, vraysun. Render

Check VRaySun default values for scene units of mm vs meter when display units is always mm
Same for VRayStereo Helper. Check default values for scene units of mm vs meter when display units is always mm

[Svetlozar Draganov]

Thank you very much for your help.
We managed to reproduce the issue and we made a note about it in our system.
We will let you know when we have update for it.

[Morne]

Hi Team, it's been more than 2 years, any new news yet regarding this one?

[Svetlozar Draganov]

We are sorry to inform you but this issue hasn't been fixed yet.

[Morne]

Seems this is at the bottom of the list?

[Svetlozar Draganov]

Yes, it is considered as a minor issue and it is a bit down on the list.

[Morne]

This is becoming very annoying. The UNITS thing also affect other things like Round Corners in VRayEdgesTex.

If it's set to 1mm in a scene with mm as scene units, but then that object is merged into a scene with meter as scene scale, it changes the round corner to 100mm! Is that a Max thing, or can something be done about it one VRay side? The 6500mm distance between eyes for the Stereo helper is another example

We can't always control where assets come from, but I would expect it to at least look the scene no matter what scene units are used

[Neilg]

It's not a bug, it's across max. In every max tool changing the scene units changes the default values of variables. Using any spinners to change values in edit poly becomes impossible with scene units in metres, and the default values for everything changes.
It's been this way forever, dont add a tool in max that has variables and dive straight into rendering without checking them first?

The way to get around this is to keep the system units the same across all projects you do and just change the display units. If you get models from a different source, convert them to your local scene units first.