"Principled v2" feedback/discussion thread

Forgive my ignorance here, I saw that there’s a build for the new Sheen BSDF, but when will a 4.0 build be available with the full PV2, meaning with all the updated shader components (energy conservation, new sheen model, etc.)?

A 4.0 build with all the relevant Principled v2 features will be available when all the features are merged.

We don’t know how long that will take since it requires Lukas Stockner (or someone else) to update the old Principled v2 code to Blender 4.0, make further changes to fix issues (Principled v2 didn’t have proper MIS if I remembered correctly), then submit it for review where it needs to be reviewed by people then merged into the 4.0 branch.


Hey even though the principled V2 has not been updated to 4.0, is it possible to download the 3.4 alpha branch now to try out and test the node since it is unknown when the node will get a new branch?

From my understanding, the old Principled v2 branch isn’t being built by the Blender foundation build bot any more and thus isn’t on their website anymore. As such the main way to obtain that build for yourself is to build it yourself, or to find a copy of the old build somewhere (possibly from another user).

1 Like

Hi there

You can reach out to me on Instagram @Anthe.cr3 and i can send you the original zip File of the 3.5 Alpha Build that has the Principled BSDF v2 in it.

Been using it (among the previous 3.4 build) for over half a year now.

1 Like

Hey I saw that transmission roughness was removed. I understand it was hard to maintain and has a bunch of issues, not being able to work with GGX multiscatter being only one of them. But do we currently with it removed lose functionality?

This is 3.6 with transmission to 1, roughness at 0, and transmission roughness at 0.8

Also 3.6 with transmission to 1, roughness at 0.8 and, clearcoat at 1 to compensate (sorta)

I’m not sure how to achieve the top result anymore, where the surface appears to be very shiny, is it possible? If it’s currently not possible will this functionality be added later?

Also if it’s still possible please tell me because I’m a silly billy :slight_smile:



Set the clearcoat to something like 4

I noticed the latest builds of 4.0 that energy conservation is now in place, and the IOR is controlling reflections. Is there any info about how the Specular channel is now tied into this? I’m seeing that specular seems to be acting as a scalar function to F0. Based on the behavior it seems that the default Spec 0.5 corresponds to the default expression of the fresnel curve, but I’m unsure and would be good to hear the specifics of the new behavior.

1 Like

According to the OSL file for Principled BSDF, here is how Specular option interacts with the specular aspect of the diffuse/subsurface scattering material types:

    f0 =F0_from_ior(IOR);

    m_cdlum = luminance(BaseColor);

    /* If cm_dlum > 0, then `m_ctint = BaseColor / m_cdlum`, other wise `m_ctint = color(1.0)` */
    m_ctint = m_cdlum > 0.0 ? BaseColor / m_cdlum : color(1.0); 

    /* Mix between `color(1.0)` and `m_ctint` based on the `SpecularTint` value (an input on the node) */
    specTint = mix(color(1.0), m_ctint, SpecularTint);

    /* `Specular` is the Specular input on the node */
    f0 = (f0 * specTint * 2.0 * Specular); 

Based on this code, it seems Specular is just a F0 intensity slider. And 0.5 is a “standard F0”. So your investigation seems to be correct.


I’m just curious, Lukas ( @lukasstockner97 ) mentioned that nested dialectrics was something being worked on. Is this something planned for the 4.0 release?

1 Like

Nested Dielectrics is listed as a “further development” goal in the Principled v2 task. https://projects.blender.org/blender/blender/issues/99447

Based on the timings listed on the other changes, this implies it won’t be added in 4.0.

Note: Nested Dieletrics is not something that will be added to Principled v2. It will instead be added as a feature to Cycles that various shaders can make use of (E.G. Glass BSDF, Principled v2, etc)


Oh, that’s good news. The use case for nested dielectrics is super specific but when you do need it, the workarounds are extremely stiff and annoying to set up.

1 Like

Great thank you. So reading that page, if the item is checked that means it’s currently implemented and functioning in the daily 4.0 alpha build?

From my experience it doesn’t seem to be.

@Christopher_Tyler The ticked items in the “changes” section at the top should be done. The ticked items further down in the " Things that need to be fixed" are probably done.

@2905710881, can you please detail some of the things that have been ticked but isn’t working for you?

1 Like

Can you please elaborate. What exactly is the issue you’re showing here?

I remember that Principled v2, which I used to use, had a Principled v2 option

The idea of having Principled v2 be selectable as a different “microfacet distribution” is no longer the intended design for Principled v2. And as such, that option was never added to main.

Instead, the Principled BSDF is simply being updated, with parts being removed, reworked, updated, and added, until it has all the features that was desired from Principled v2.

So right now when you select GGX/Multiscatter GGX, you are actually using the currently in progress Principled v2.