Displacement - 32bit capping negative values

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Displacement - 32bit capping negative values

Postby stir » Thu Jan 10, 2019 1:02 pm

stir Thu Jan 10, 2019 1:02 pm
Hi.

Why is the displacement capping the negative values in the 32bit displacement?
What am i doing wrong?

Octane_Cap_32bit.jpg


The displacement is a 32bit exr. I have dobbelchecked that there is values innside After effects, and there is negative values in the black and positive in the white, like a normal 32bit displacement.
So there must be something i do wrong innside Octane.

-I create a material
-Displacement node in the displacement slot
-RGBimage in the texture slot
-Set the midlevel to 0 ( from what i understand is midlevel should be 0 for 32bit and 0.5 for 16bit)


I also tried changing gamme and change channel type from Auto to 32bit innside the RGBimage node.
No luck.
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Re: Displacement - 32bit capping negative values

Postby paride4331 » Thu Jan 10, 2019 2:31 pm

paride4331 Thu Jan 10, 2019 2:31 pm
Hi Stir,
you should to set mid level to 0,5 (0 black - 1 white)
Grayscale image instead of RGB image.
I think your issue depend on normals in your object, try to flip them, you should solve your issue.
Regards
Paride
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Re: Displacement - 32bit capping negative values

Postby stir » Thu Jan 10, 2019 7:09 pm

stir Thu Jan 10, 2019 7:09 pm
Hi Paride, Thanks for the reply.

Sadly, that ain't solving it.
RGB or Greyscale doesnt seem to do anything.
And changing the midlevel just inflates or deflate the mesh like a balloon.

I also did a second pass and made sure the normals were pointing correctly. Also did a reset Xform to be sure.

So i think the bottom line is, that octane dont work with negative values.
Because like you say (0 = Black and 1 = White).... what is blacker then black then?
So when there is places on my displacement map that is between the range of lets say -0.1 and -0.23 they will all cap flat to 0 because Octane consider 0 and below as 0.

Im going to try research if it possible to squeez the values from the 32Bit displacement (minvalue -1.2 maxvalue 2.3) in to the 0-1 value range that octane work with.
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Re: Displacement - 32bit capping negative values

Postby paride4331 » Fri Jan 11, 2019 8:40 am

paride4331 Fri Jan 11, 2019 8:40 am
Hi stir,
I still think it depends on geometry, could you try to apply your displacement map to a simple plane?
Does it work?
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Re: Displacement - 32bit capping negative values

Postby Maskeline » Sat Jan 12, 2019 6:45 pm

Maskeline Sat Jan 12, 2019 6:45 pm
I have the same problem
I am using the octane with maya, and the negative values of a displacement leave them in o (flat). The same thing happens with values that pass 1.
I'm doing it on a plane. It can not be for normal
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Re: Displacement - 32bit capping negative values

Postby paride4331 » Mon Jan 14, 2019 10:51 am

paride4331 Mon Jan 14, 2019 10:51 am
Hi Maskeline,
could you share your scene (in PM) to check the issue you reported?
Regards
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Re: Displacement - 32bit capping negative values

Postby stir » Tue Jan 15, 2019 4:33 pm

stir Tue Jan 15, 2019 4:33 pm
This is a good read.
Some of it is Vray specific.

https://www.cggallery.com/tutorials/displacement/

But the theory behind 32bit and positive and negative values is still relevant.
I belive you would not be able to replicate what he does on that webpage in Octane with a 32bit displacement.

The workaround is to use 16bit displacement instead, and to be fair, 16bit displacement is perfectly fine and is more flexible when it comes to modify the map itself.
BUT.... 32bit displacement is known to have more accuracy.

It would be nice to keep this talk going until we are on the same page.
Because it seems Paride still means we are suppose to be able to do this.

And i would love to be wrong about this ! :D

Cheers
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Re: Displacement - 32bit capping negative values

Postby SergKlyosov » Wed Jan 16, 2019 5:54 pm

SergKlyosov Wed Jan 16, 2019 5:54 pm
Hi Stir,

In that article which you showed above - author is using single channel map, it consists only from Red channel the rest of a channels are black.

I've been facing similar maps from Quixel megascans and for some reason octane doesn't recognize them.
How to properly use this kind of maps, where is only one red channel exists?

Paride, maybe you can give us an answer

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Re: Displacement - 32bit capping negative values

Postby stir » Wed Jan 16, 2019 7:30 pm

stir Wed Jan 16, 2019 7:30 pm
Yes

The RED channel workflow is handy, keeps the file sizes to a minimum.

But like you, i also noticed Octane doesn't recognize these maps.

So what i do is, in some software you can tell it to populate all the channels. Like in Zbrush you can tell it to use all 3 channel, i dont know about Quixel.
If you dont have the option you need to copy the red channel in to the remaining channels using a composition software. (nuke,ae and so on)


Would indeed be interesting to know Paride/Octanes view on this.
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Re: Displacement - 32bit capping negative values

Postby paride4331 » Thu Jan 17, 2019 9:03 am

paride4331 Thu Jan 17, 2019 9:03 am
Hi guys,
you can obtaine a correct texture into Octane but at the end you have to use a baking node so to speed up the process would be converting to grayscale in photoshop.
something as in this case: https://render.otoy.com/forum/viewtopic.php?f=30&t=56508&p=289968&hilit=+megascan#p289968
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