VRay Sun, Sky and Physical Camera video tut + Bonus Script!

[RSI]

Hi Lele, I'm using your workflow from a long time now, and I like it, the light distribution look more natural so thank you. But I have some problems with interiors too.
Can you take a look at my post:
http://www.chaosgroup.com/forums/vbu...ad.php?t=44372
And tell me if you think about a solution?
I can send you the scene if you want.

Thanks

[^Lele^]

Sure thing.
Sampling in the dark areas is harded, as the difference between pixel intensities, before gamma is applied, is very low.
My first suggestion would be to lower the AA threshold (use DMC AA, and change the threshold there), so to make vray sample better in those conditions.
Vray, unless you turn sub-pixel mapping on, will first render, and then apply the gamma.
So the second suggestion would be to turn sub-pixel mapping on, and see if it cures it without changing threshold.
That should result in vray applying the gamma before AAsing the samples.

Let me know how it goes

Oh, i didn't notice you had no gamma applied in the color mapping.
If that's the case, set gamma to something like 2.2 and check "dont' affect color (adaptation only)".
That will sample the image as if gamma 2.2 was applied (hence "stretching" the difference between pixels in the dark areas), and make a MUCH better job of it where it's darker.

[RSI]

Thanks Lele, i will try it tonigh!
or tomorrow depending of my girlfriend rules...

[^Lele^]

Lucky you you have one.
On a similar note: do you set AA that mad high on purpose, so to spend more time with her?
Adaptive subdivision at 3-7 is something that would give me nightmares.
That's asking VRay to render the image 9 to 49 times bigger, and then interpolate.
Sure as hell it's gonna be clean...
Make sure you switch to DMC AA, if you want to use "high" numbers.
For images like those, with DMC AA, i'd go for a 2-12 and render likely a few times faster than it does now.

[DzineTech]

Lele, I've been experimenting with your theory and scripts over the last week and I've got a few issues which I hope you might be able to clarify for me. I've been testing out your exposimeter which I thought was a tool which would analyse my scene and expose my phys cam ISO so that no pixel would be >1 when a white override material was applied. As the scene was an exterior and I used the appropriate preset, ticked the white balance option and the script exposed the scene reducing the ISO to a new value. When I did a render with the override mtl still on I was still getting a fair amount of pixels which could be clamped. I found that the lowered ISO value was close to the value I ended up using so its good for getting a "ball-park figure" Was I doing anything wrong or was the exposimeter not intended for such use?

Secondly, I've been playing with your phys_mats script which is a great time saver. I've been wanting to use your script in a quad-menu but I dont seem to be able to do so. I've tried amending the script by giving it a name and adding it to the category that the rest of your scripts are found but it gives me errors. Can you tell me what needs to be done to achieve this?

I'm not sure but I think I've got a slight problem with the script. I have a vraymtl which has a tile-map in the diffuse slot. The Tile-setup has a bitmap texture so by default has an output rollout however your script seems to miss this and puts the tile-map in an output map instead. This isn't ideal because it causes problems with the UVW mapping of my multi-subobject material for some reason. Can this be resolved?

[^Lele^]

The exposimeter in itself doesn't guarantee that no pixel will end up being below 1.
That WOULD be the case IF you had an evenly lit white plane in front of the camera.
That's why, however, you have the exposimeter areas to play with.
If you show me an image, i'll likely be able to tell you what settings to try out.
As far as the script goes, just add this line at the top, and a matching closed bracket at the end, like so:

macroscript vrayMatsChanger category:"Lele's Vray Tools"
(
/*script here*/
)

After running it, you'll find it with the rest of the scripts.

[DzineTech]

Lele, thanks for the code, script activation works as expected.

Getting back to the render theory...

I was running tests yesterday on my exterior scene where I used a 0.6 rgb multiplier but I wasn't happy with the image as I felt it was too dark, especially the sky. I tried lowering the rgb multiplier further to 0.3 hoping that rexposing the scene would brighten the sky but it didn't.

I feel like I going round in circles trying to get this to give me the results I want but no luck so far. My workflow is:

1) Place camera in scene and put a white vray material in the override slot. The material has a vraycolour map in the diffuse slot and is 254,254,254 RGB and 0.6 RGB multiplier.
2) Ensure all materials in scene have this same 0.6 value via you physmat script.
3) Expose scene via lowering ISO values till all pixels rendered are <1.0 float. Doing this manually, not with the exposimeter.
4) Turn off override and render normally.

when I complete 3) I can see the vraysky is looking darker and has less saturation than what I would like. I would like to avoid using the colour map on the sky as sunsets look false. Is there somewhere in the above workflow that I have gone wrong, or could it be that the vraysky no longer works with this method in SP3, or perhaps camera exposure has since changed?

Thanks

[^Lele^]

The sun and sky HAVE changed since when the tutorial was written, yes.
Keep the method as a mean to achieve faster GI renders (due to less light bouncing around) and to manually compensate for the sky brightness.
It would need some further, fresher testing, but i believe the top albedo (for white stuff ) one should attempt to get feasible results with the physcam, sun and sky (ie. matching a real world picture), should exceed 0.8 for snow, and 0.6 for white paint.


As a side note, exposing does NOT change the scene SATURATION (sky included), rather, only its brightness.

[STUDIO_ARCHITECTS]

Hey Lele
Can I still find these videos somewehere....all the links are down?

Hope you can help
Cheers

[^Lele^]

the VRayElite one seems still to work, here.
Let me know if it's not for you.

[R_Cyph]

Hey all,

Its been a while since I've chimed in on this thread. Does this tutorial still apply? Have the VrayMTL been changed or updated in 2.0 compensate for Sun/Sky or very bright values

[^Lele^]

just a heads' up:

while there are no hosts anymore, there is STILL something lurking on the web:
magnetxt=urn:btih:8b19387f101265e32cb3ba55d7a024190ae3e7 3d&dn=physcam%20tut&tr=http%3A%2F%2Finferno.demono id.me%3A3406%2Fannounce

[wxyz]

Couldn't get the link to work. I'm still running Max 2010 just to use this script.

[^Lele^]

it's a magnet link: use a bittorrent client (the installer will make the system react to those).
In case the installer doesn't, just "add new torrent" and copy/paste the whole link.
You can then choose to download just the 3kb script if you so please.

[wxyz]

Thank you for your generosity