Comprehensive Detail: Physical Surface for P11


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    Next question: Can this root node do rust on metal? Or ... layers? I'm going to try some things in that area next.


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    One last SSS: Strawberry Jello. Just for a giggle.

    0_1464115964088_Strawberry_Jello.jpg



  • The main purpose of the Physical Surface root is to allow for compatibility with maps out of programs like Quixel Suite and Substance Designer/Painter. Can you use nodes with it? Sure but it's really more focused on supporting maps like Albedo, Metallic, Roughness, etc. without the fuss of having to fiddle with nodes.
    0_1464117718355_1463017743183-compare-resized.png
    0_1464117726595_1463018237280-mat-resized.png

    In the images above the entire bathtub (tub, faucet, plunger, etc) is one material called bathtub. Using Substance Painter, I assign various parts of the object a material or I paint in some extra details etc. Then I export out the maps and plug them in as shown in Poser. That one material, using those four texture maps from Substance painter creates the look of multiple materials on the one object without a bunch of fancy node work to make it so. Handy for people working in games who use Poser or for folks wanting to minimize the material count in a model or just for folks not wanting to deal with nodes.


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    @bagginsbill said in Comprehensive Detail: Physical Surface for P11:

    Another goal (although, IMO not met) is it should be possible to do a multi-material in PBR style using PBR maps alone.

    ^^^^^^

    I have some problems with the fidelity of the reproduction. I see weird behaviors that cause the specularity to do very non-physically based behaviors, so that is why I say "not met".


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    @Teyon : Thank you so much for that clarification. We all need to know these things. This is great.

    @bagginsbill : Here is a challenge. On a separate layer I have a sand texture to roughen a rust texture. I also have clouds transparency map to separate the metal from the rust. How do I apply the bump/displacement ONLY to the designated rust areas? Another point ... How do I make the rust area on the second layer, darker? I urealize it is a secondary texture to the propriatory base layer but I'd like to see it more robust and darker.

    0_1464123662218_Rust_Test.jpg


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    Rust test 2, what do you think?0_1464126958454_Rust_Test2.jpg


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    Hi. Sorry I'm behind - have so much work. You're making progress on the two-layer effect and I can help improve it, but as Teyon showed, the purpose of the Physical Surface node and multi-effect maps is to produce that effect in a single layer.

    It's fine to investigate layers as a tactic for certain effects, and rust could be one of those that makes sense. However, in the context of a thread devoted to the PhysicalSurface node, this is the wrong way to go about it. Not wrong because it doesn't work, but wrong because it is non-responsive to your own question, which basically is "what is this thing for and how would I use it". Teyon showed how you use it. It doesn't involve layers.


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    Here's a demonstration of (one of) the non-physical behaviors I see when using the misnamed PhysicalSurface node. (SuperFly only - I won't bother doing any demo with FireFly unless you need that for some reason)

    Here is a basic scattering material with a mildly blurred specular reflection, a skin-like pink color in the diffuse reflections, and some blood-like subsurface scattering. This isn't exactly like skin, but it isn't exactly unlike it either.

    The left-most pawn material is using my old standby Scatter + Blinn shader, connected to the legacy PoserSurface root node. I consider this to be the best, most physically correct shader that can be done with 5 or less nodes. (It is probably the one I use 99% of the time.)

    The middle pawn material is using only the PhysicalSurface root node for the entire effect.

    (We'll get to the third pawn in a minute).

    alt text

    Look at the sky reflection on the pawn head. On mine, the Fresnel effect is set correctly for a material with minimum reflection at 4% for surface pointing at the camera. The middle (PhysicalSurface) minimal reflection is way more than 4% and this is not physically correct for the material I'm trying to do. There is no way to fix it either.

    Now look at the sun reflection on the pawn shoulder. (The flat ring around the "neck")

    On my Scatter+Blinn, the sun is properly reflecting a very bright white. But on the so-called PhysicalSurface shader, the sun is unnaturally subdued. There is no physical basis for this - the reflections on this shader are wrong both in facing the camera and at a shallow angle to the camera. It does not behave with the proper Fresnel effect (first of all) and it does not let me adjust the effect properly for the material I'm trying to do. It always presents with this over-glazed look that makes everything seem like silicon. Yes you can make the Specular color darker, but then you're subduing ALL reflections, not just those facing the camera, and while you can get what some would claim is a nice effect, it's NOT PHYSICALLY CORRECT. Mine is.

    Now for added confusion, look at the third pawn on the right. This is using exactly the same PhysicalSurface shader as the middle pawn, but with one tiny change. The scattering distance is reduced to near zero.

    Mysteriously, this pawn shoulder displays the full sun reflection like it is supposed to.

    Now - I ask you - why would subscatter attenuation be a legit reason to alter the surface reflection characteristics? (Answer: it would not. This is bogus non-physical behavior.)


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    Here is another render but with the environment blacked out so we only have the sun light.

    You can see that left and middle have scatter while right does not.

    You can also very clearly see how the specularity of the middle shader is very, very wrong.

    alt text

    However, while I'm pointing out flaws, I must mention the mysterious artifact I see in my favorite shader on the left pawn. The bottom corners are "lit" in a very non-physically motivated way. I surmise that there is a bug in the SubsurfaceScatter node that is NOT manifest in the PhysicalSurface.

    Very mysterious, this SuperFly. It's almost as quirky and troublesome as FireFly. It's an improvement, but still not what I expect in this decade. Sigh ...


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    @bagginsbill , Wow, this is fascinating. I always had the impression that the physiscalsurface root was more for non-biological models. (inspite of Charles' example in the SmithMicro blog about SR4). I would love to see more examples on the strenghts and weaknesses of the node here as per the OP. I will however start a new thread on layering. I think there is a lot of potential there.


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    I was working on a tutorial for you regarding rust on metal but now I'm distracted by an apparent bug in the shape of the 3d procedural textures. I see artifacts in your renders, too with my test pawn. What the hack is going on?

    Meanwhile, a sneak peek.

    alt text



  • @bagginsbill said in Comprehensive Detail: Physical Surface for P11:

    I was working on a tutorial for you regarding rust on metal but now I'm distracted by an apparent bug in the shape of the 3d procedural textures. I see artifacts in your renders, too with my test pawn. What the hack is going on?

    Meanwhile, a sneak peek.

    What kind of artifacts?


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    For myself ... I did notice a stretch in the curve of the pawn's shoulder and again at the base. like texture striations.


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    @Boni said in Comprehensive Detail: Physical Surface for P11:

    For myself ... I did notice a stretch in the curve of the pawn's shoulder and again at the base. like texture striations.

    Exactly. Look at my sneak peek. Look closely at the all-silver and the all-rust. Both exhibit weirdness on the shoulder and base. I see similar stretching along the square edges/corners. Pretty much wherever the curvature is rapidly changing, something is wrong.


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    I thought that was user error. I thought I had applied the texture incorrectly. I used global coordinates and that helped a little, but it is still there as well as the "unlit" side showing a lot more shiny than it should as well as smooth.


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    Wow this is getting more and more mysterious. I went back to Poser Pro 2014 and rendered with various procedural 3d texture nodes and everything looked fine.

    In Poser 11 I tracked my current artifact to a Spots node, so I made a shader with JUST a spots node for diffuse color in both PP2014 and PP11 and the PP11 one looked wrong. So then I saved the PP2014 prop to my library and loaded it into PP11 next to the one I made in PP11. They rendered differently!

    Then I copied the shader (select nodes, copy, switch materials, paste) from the PP2014 prop to the PP11 prop. Even though they were constructed identically. They still rendered differently! They also render differently in FireFly, so it's something to do with P11, not with SuperFly.

    Here's a PP11 Superfly render of the spots shader on two pawns. The left pawn was saved by PP2014. The right pawn was saved by PP11.

    alt text

    Again - I copied the shader from left pawn to 2nd pawn. There is no visible difference in the shader. So I'm thinking it's either a geometry bug or a deeply unobvious shader bug.


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    The in-memory prop seems to be corrupted somehow.

    When I load new pawns from library, they do not show artifacts. When I copy those they do not show artifacts.
    When I clone one of these "corrupted" pawns, the copy also shows the artifacts.


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    If I save a corrupted pawn to the library, and then load that, it is still corrupted.


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    So - I do not know how this problem was created, but I now know how to fix it.

    You have to just abandon the prop - it is corrupted.

    I found that the shader is not corrupted. So here's how I fixed it.

    For each corrupted pawn:

    • Save it's material to a temporary file in your library
    • Delete the corrupted pawn prop
    • Load a new pawn from the library
    • Apply the saved material

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    OMG what a dope I've been.

    So I'm happily working on the shader -- no artifacts. Then I notice that the pawn looks sketchy in SuperFly because we don't have polygon smoothing. No problem, turn on one level of subdivision. I had done that before as well.

    Oh --- no --- the artifact is back! The artifact is caused by subdividing the pawn!!!!!!! That sucks.

    So - now we know the cause as well. And I can proceed with the shader work and deal with the subdivision at some other time.