Vray bump brdf material issue

[corentin_provost]

Hello everyone,
I'm encountering an issue with the Node Bump BRDF in V-Ray for Houdini. When I add a normal map, it only seems to work correctly if the mesh is a V-Ray proxy. However, if I apply it to a regular mesh or a Houdini cache, the normal map gets ignored or doesn't render properly. I'm using the latest nightly build with Houdini 20.0.563.

The worst part is that I've already managed to render images with the behavior I was hoping for, but the result seems completely random and just doesn't work anymore.

Unfortunately, I can't use the `.vrmesh` format as a workaround because I rely on point attributes as masks in the shader, and `.vrmesh` doesn't support these attributes. Has anyone else experienced this problem or found a solution?

Thanks in advance!

Coco

[tobiasroesli]

Hey, I don't have a Houdini in front of me but maybe you need packed geometry for that. I never work with vrproxy's but I guess they're packed geometry like alembic.

For me the best workflow in Houdini is to work with packed alembic's. it is very fast because its natively supported from vray. For example if you have a houdini bgeo file it first hast to convert it into a alembic internelly which takes a lot of time with bigger geometry's. If you stick to packed alembics you almost starts to render after you hit the render button .

For your case just try a packed sop in front of the material sop. or an alembic rop and alembic file node in front of the material sop.


Cheers

[corentin_provost]

Hi Tobias, thanks for your fast answer. The idea seems pretty cool, I actually tried this morning and my normal map was working correctly but I had some displace artifacts I did not have before so I let it go and decided to finaly post here.
Anyway there is one thing I did not try yet, it's to try using a vrscene directly rather than a vrmesh or an abc.

But deeply I think there might be a global problem in houdini to blend or add normal maps, I was not able to chain normal maps in houdini like I usually do with other renderers.

This might 100% be my fault as I may forget something obvious but for now it seems complicated to chain normal maps.

One thing I forget to mention, I am using a triplanar for my added normal map, I know it's not always the better solution but once again It's randomly working...

Cheers

[tobiasroesli]

Hey, Triplanar isn't supported with GPU yet, as far as I know. Only Bitmap.

[corentin_provost]

Full CPU here, not taking any risk with GPU yet ^^

After further investigation, looks like the blendBumpNormal I have in my setup doesn't produce any result, should I keep my bump settings in my material to normal (tangent) if the upstream node is a blend bump normal ? And once again, the node itself seems to work properly if applied to a vrmesh...

[Dubbie99]

I have never had any luck getting the blend bump normal to work in Vray4Houdini

[tobiasroesli]

Me too, but I use mostly GPU rendering and Triplanar and so I have to stick to bumbmaps and if I need to blend them I simply use a layer node

corentin_provost I can't help you with that But I would guess so... Still strange with this vrmesh. Have you tried if there is something with packed and unpacked geometry which could influence that?

[corentin_provost]

Hi guys, thx for your compassion eheh, but yeah I am trying like hell to get something kinda basics. Worst is really is this "proxy" thing, I'd like to know if proxies are computing some informations like normal / tangent / uvs, that let the bump blender work.

[Gosho.Genchev]

Hey corentin_provost ,

I did a quick test on my end, and the setup (Bump Blend into Triplanar into Bump Material) appears to work on my end. I've attached a screenshot and my Houdini file.

If possible, could you send us a HIP file to troubleshoot the problem with your scene? Dubbie99 , the scene may be interesting to you as well - the Blend BumpNormal texture should work just fine.




Best regards!

[corentin_provost]

Hey hello Gosho ! Thanks for your reply, nice to see your node setup on this, I did not know I could do something like this and I will give it a try.
I can not really give you a hip right now but I will certainly try to do as soon as I got time to reproduce the bug.

Sure thing is that this normal / bump blend thing is not working with a native houdini object, but as soons as it's packed / or read from disc with a .abc or .vrmesh it works. I would like to know more about the vrproxy exporter, if it does internaly some cleaning operations for example.

Other weird thing, but this might me 100% my fault, can I use a bump mtl after a blend mtl ? I have a blend material breaking if I use a blend mtl after. Maybe they need to stay at the end of the chain.

I'll give you a scene ASAP

Cheers
Coco

[Dubbie99]

thanks for the Demo scene Gosho.Genchev -I'll check it out. I had pretty much given up on that node ever working.