Hi there,

I have this character I'm working on. I took a swing at Arnold (for Softimage) and it's great.
I thought I'd do a Mantra rendering in parallel as well, but as you can see I had no luck.
My guess is I'm not turning the right knobs.

If you want to see more Arnold rendering while I progress with texturing go here [si-community.com].

Mantra






Arnold

Look great. I am learning Mantra myself because of the contest.
I would be more than happy to try and ‘turn the right knobs’ as an exercise if you care to share.

More than happy for you to just share a piece of the geometry for testing purposes.

redaborchardt, thanks.
The problem is that the VD maps are quite big and I'd have to use a file sharing site and that comes with needless (at this point) complications.
For now I'll work on what I need to do to finish this and if in the meantime nobody else sheds some light on this, I'll look into methods for sharing these big files.

Of course, if you insist on getting these files and you come with a solution for me to send you the files effortlessly (like not creating an account on a file sharing site), I'll gladly toss these in your direction.

to hunt down your problem, can you make a sphere, sculpt on it a bit, then make your VD map (low res) and post them here?

Here you go arctor.
Doing this test actually helped because as I was setting up the settings in the displacement tab of the Mantra surface shader, I forgot to change from ‘displacement along normal’ to ‘vector displacement’ and voila, it worked!
But, I soon realized it's not on “vector” and it's not like I care what is says there, but redoing this on the head, Mantra's displacement generation is lacking a lot more in terms of details compared to the Arnold one. Pretty sure it has to do with not being generated as vector but along normal.
The same goes for the sphere - normal works, vector doesn't. At least, on my side.

the attachment is too big. limit 5 mb

Can you do a quick render to see what I am aiming for?

Below is what I get using a standard Mantra Surface node. Looks about right given the texture. What do you think?

McNistor
Here you go arctor.
Doing this test actually helped because as I was setting up the settings in the displacement tab of the Mantra surface shader, I forgot to change from ‘displacement along normal’ to ‘vector displacement’ and voila, it worked!
But, I soon realized it's not on “vector” and it's not like I care what is says there, but redoing this on the head, Mantra's displacement generation is lacking a lot more in terms of details compared to the Arnold one. Pretty sure it has to do with not being generated as vector but along normal.
The same goes for the sphere - normal works, vector doesn't. At least, on my side.

Yes, I am getting the same. I missed your reply.

Well? Is it us or is it the Mantra surface shader?

We are having some issues with Vector Displacement in Mantra. I'm looking into it now.
Renders works perfectly in Softimage with Arnold, but looks shockingly bad in Mantra.

Same thing here…Displace along normal works, but lacks detail that Arnold clearly shows. Vector Displacement does not work in tangent space which we need because of deformation on the object.

Will post my findings here if you don't mind McNistor.

No, please do post here.

Cool character by the way.


Here is my examples. Using the principle shader which also does not work.

Last one is Arnold. Note the lovely overhang skin on the back legs.

Thanks for these Werner. It seems that VD is broken in Houdini.

Your example displacement texture is encoded XZY. Have you tried swizzling the texture output going into the displace vop?

No, I did not.
Thanks jsmack, I'll try this when I'll get back on this.

After researching vector displacement, I have found that every paint app encodes the map differently, and some, (ZBrush), support dozens of permutations of the encoding to try to support all the different ways a renderer could interpret the map. This issue seems like one that would be hard to try to account for with a shader interface. Fortunately, Mantra is flexible enough to allow one to ‘roll your own’ decoding, and reverse engineer almost any map using UV tangent or world space.

see:
http://docs.pixologic.com/user-guide/3d-modeling/exporting-your-model/vector-displacement-maps/ [docs.pixologic.com]
https://support.solidangle.com/display/AFHUG/Vector+Displacement [support.solidangle.com]

It is probably worth a bug/rfe to add alternate encoding support to the built-in shaders that handle displacement.

Actually Mantra is very capable to render vector displacement. The problem is that there is no common norm how to export vector displacement maps. Each app has it's own export type with RGB channels swapped ( like jsmack said ) or inversed. ZBrush has an option for that, which unfortunately is just a cryptic single integer. It's under Preferences > ImportExport > Tangent FlipAndSwitch. For Houdini / Mantra you need to set it to 42.

Here's how you need to prep the textures before they go into the displace vop:

From Mudbox:
-R -B G

From Zbrush:
( with default FlipAndSwitch 1 )
-B G R
( with FlipAndSwitch 42 )
R G B

I did those test a whole while ago, but I dont think much changed. No idea about 3DCoat though, because it didn't have vector displacement exports at that time.

If you're lacking micro detail, then you can check “Add Bump To Ray Traced Displacement”

Thank you Mariusz for this piece of valuable info.
When I'll need to extract other VD maps from Zb for Mantra I'll make sure to use your settings. For this one I'll implement jsmack's suggestion since it doesn't require another map extraction process.

It can also be worthwhile to increase the Shading Quality on your object. The default of 1 doesn't always do displacement maps justice. And nice looking work McNistor.

Thanks man, I'm yearning to do better
I've payed no attention to shading, lighting and render settings in that Mantra render as the initial displacement result threw a big wrench in my “produce Mantra eye-candy” gears.
When I'll have something I deem worth showing from Arnold I'll get back on this and try to match it.