Differences in glossiness from 32 bit source and caustics from vray 2.3 to 3.0

[mmadail]

Hi there,

At work we have just updated to vray 3.

We have a scene that we rendered when we were using vray 2.3, that has a coin with a painted 32bit TIFF bump and glossiness map. We also had caustics set from a normal spotlight source.

Now we had to revisit this old scene and we were surprised to see that there are huge differences in the way the glossiness is being interpreted. Although it is the same exact map, now instead of having some glossy reflections, it's like i've pushed the glossiness almost to 1, where it would be like .8 or so.

Also, the caustics are completely gone despite everything is turned on as before, nothing was touched.

Any ideas why is this difference? And it looks like vray 3 is actually darker than before.

Please see this image comparision.


Render on the left is the correct version, as you can see on the right, glossiness is completely wrong, there are no caustics on the floor, and the overal black is darker on the coin than it should. Map is the same for both renders, and turning off colorcorrect makes no difference, it's still wrong.

So far, i've managed to find out that this is a difference from vray 2.3 from then on. Version 2.4 produces the same different result.

Thanks in advance!

[tashko.zashev]

Hi,

A lot of things have been changed since the V-Ray 2.3 version was released, but this render difference is quite big.
Would it be possible to send us your file to support@chaosgroup.com for investigation?

[madail]

Hi there Tashko,

Thanks for your reply.

Well, i've been testing several things for a few hours and i think i found some answers. This is what i've tested

-open same scene on max 2014 - vray 3
-open on max 2014 - max 2.4
-open on max 2013 - max 2.3

This difference occured in both vray 2.4 and 3, and in max 2014.

After reading some stuff regarding gamma changes, i found out that in max 2014 the gamma settings changed quite a bit, and there is no longer an option to change input and output gamma for bitmaps, so i wondered if the problem was not in vray, but rather in how max was importing maps, so i reloaded my map, and instead of setting it to automatic gamma, i changed it to inverse gamma of 0.45454, and i managed to replicate the same "correct" result that i had with max 2013-vray 2.3..

So in fact the problem was that max changed the default input gamma for bitmaps...

The only thing that really changed in vray was the caustics. As you saw in my image, the new render did not show any caustics effect, but it still calculated the map, so i tried bumping the light multiplier a lot and i managed to get caustics again. So i think that is the only change. You now have to set a really high multiplier to see the effect, where in vray 2.3 you didn't.

In the end i was able to replicate 99% of the result in max 2014-vray 3, so i think all is good

Thank you!

[tashko.zashev]

Thank you for the update. Yes, the 3ds Max auto gamma mode was introduced in version 2014, which often lead to issues when render older scenes. However, I'm glad to hear that you are now able to replicate the render result from 2.3.

About the caustics difference, I'm going to run a quick tests to check if there is an issue with the caustics multiplier.

[madail]

Hi again,

Very well then, please let me know how it goes.

[tashko.zashev]

There are no caustics difference in my simple test scene - V-Ray 2.3/Max 2013 and V-Ray 3/Max 2015.
Here is a screenshot :


Make sure that your VFB gamma settings are identical in both versions.
Is it possible to see your scene file?

[madail]

Hi Tashko,

Thanks for trying it.

I can't see your attachment nor post my scene file because i haven't got permissions for it..

[tashko.zashev]

Hi Madail,

I've uploaded the screenshot here: https://db.tt/QbQ9q4UD

I can't see your attachment nor post my scene file because i haven't got permissions for it..

Only our customers can view attachments and post files.
Please send us your dongle serial number to support@chaosgroup.com and we will check whether your forum account need to be updated.

Thank you.

[madail]

Hi again, and thanks!

Yes i know about that limitation.
At home i don't have a licensed vray... only in our company, which we updated to v3. I'll have to check with my boss for that

Thanks for your help!