xnormal vray workflow?

[super gnu]

this is something ive never really dabbled with but i now need to.

ive got an 8million poly 3d scan of a person and i need to decimate it and apply a normal map based on the fullres version.

ive been advised to use xnormal which i have downloaded.

so far i have:

loaded fullres mesh and decimated versions as obj into xnormal, chosen file name and resolution (8k) , left all other settings at default.

hit render, and it has spit out a reasonable looking normal map (well its the right colours at least )

brought low res mesh into max and applied vray material. added vraynormalmap in bump slot and vrayhdri map in the normal slot of that. loaded xnormal generated map into hdri loader..

when i render i get a vague suggestion of detail but its very feeble and in no way gives that "is it the full res mesh im looking at?!" effect ive seen with normal maps..

i also have no idea how to display the effect in the viewport as ive seen demonstrated.. that is a minor thing tho.

edit: Seems its a vray /material issue as i tested a normal map that was provided with a sample model, and i get the same weak effect. ive tried increasing multiplier and bump strength from 30 default, but it just ruins the model shading.

[Ihno]

For nomal maps the problem is often gamma:
https://forums.chaosgroup.com/forum/...s-gamma-or-not
Bump strength should be 100.

[super gnu]

bump strength should be 100?! when i turn it up that high my mesh looks practically inside out. i tried every combination of gamma settings and even tried disabling the colour management of max entirely. however i *didnt* try fiddling with gamma when bump was at 100.. maybe i had wrong gamma when i tried that.


thanks for the pointer, ill check it out.

[Ihno]

What file format are you saving? Xnormal writes exrs in linear space.
8Bit's like tga are srgb.

bump strength should be 100?!

I think so, normal maps are basically angle information. Its kind of a by-pixel-surface angle offset.
(Apologise for the superficial knowledge to every one who really understants whats going on. )
So, theoretically there should be only one right angle (the one from the high poly surface).
I think that map amount as well as the multiplier in the VrayNormalMap node kind of blends the effect in.

IMO normal maps that are supposed to simulate mid-frequency details aren't working very well when used in a ray tracer. (at least not up close)
I think this is because there is no geometry for the light, there isn't a curved surface for the Light/GI to create the right kind of gradient. For me that completely screws the effect.
In the reflections it works pretty well but the lighting kind of breaks it.

As well as bump maps they can work very well on high frequency details.

In real time engines normal maps which are covering bigger differences between high and lowpoy are working much better since everything is fake and there is no GI (at least nothing nearly as detailed).
You bake AO maps based on the highpoly so the fake GI is also looking highpolyish.

PS: Mid frequency also won't work too well on everything stereo related. f.e. VR.

Edit:
One thing to add.
The lowpoly surface you're using sould be exactly the same as used for baking.
I usually use obj for exporting to xNormal. So I dont know if there is something to be careful about in the FBX exporter in that regard. But you don't want it to mess up (optimize) the normals or anything else.
You'd have to reimport the lowpoly model then.

[super gnu]

yep.. it was, as you said. i had tried bump mltiplier of 100, and i had tried fiddling with gamma, but i hadnt tried doing both at the same time. using hdri loader for normal map set to gamma 1, and 100 for the multiplier sorted it right out.

regarding what you said re mid-frequency details and shadows... ive often wondered about that with regards to vray.

unless my memory is flaky (it is) back in the day when finalrender was the big thing.. they introduced "bump shadows" which deformed the shadows cast on an object based on the bumped normals.. i wonder why i never saw such a feature in vray , even (blimey) 15 years later.. iirc it worked well.

having said that i can find no mention of it anywhere now.. maybe i dreamed it.