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Thread: The most difficult surface to simulate...

  1. #1
    Pancakes! IMI's Avatar
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    The most difficult surface to simulate...

    The most difficult surface to simulate...

    I say it's glass (with skin being a very close second).

    <rant>

    I couldn't add up all the time I've spent messing about in LW over the past few years trying to get good, passable glass. There have been a few times I thought I had it pretty good - you know, after staring at my screen for an hour or so, continually tweaking in the surface editor, moving the light, changing the refraction and reflection, caustics, double-sided, non-double-sided....bump and let's not even get into how the teeniest bit off the specularity is can turn your glass into plastic...

    And then when I finally think it looks good - these mental images of a million glass visual memories distorted by what my brain is telling me looks "right" on my screen, I get up and go into the kitchen...

    And there, on the countertop, left to irtself all day from the morning, 12 hours previous, is a *real* glass which at one point had orange juice in it. The sunlight through the window is causing real caustics as it passes through not only the glass, but the ever-so-thin film of dried orange juice. And it has smears on it; fingerprints; imperfections within it. Looking at it at just the right angle, there is a faint hint of the spectrum of light.

    In spite of the fact that it needs to be washed, it really is a beautiful thing.

    I return to my 'puter room and look at the glass on my screen, and it most definitely is *not* a beautiful thing; it's 'flaws' are overdone, it looks like it was never even touched by anyone, let alone used for anything, and there is no spectrum... it's just.not.right.

    Why must glass torment me so?!?! I know it can be done - I've seen it done, and done exceedingly well!
    </rant>

    I suspect this is why there are so few glass monsters and spaceships in CG.
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  2. #2
    Valiant NewTeKnight Matt's Avatar
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    Skin is definately a holy grail of CG, because as humans we are so familiar with it and can detect the slightest differences from reality. In fact any surface with sub-surface properties, wax, porcelain to name a few others are difficult to acheive.

    Out of the manmade materials, a good carbon fibre surface is pretty difficult, and I've never managed to achieve a decent spark texture finish on metal (think of the specular finish on a silver iPod here) anti-aliasing always seems to smooth it out if you're not careful. Glass is reasonably simple I would say, as is shiney chrome. The trick with both of these is what the material reflects.
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  3. #3
    naaaah, just slap dielectric on there

    hardest for me : industrial metals. (aluminium tanks, rusty frosted steel,...)
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    CORE 5718 mattclary's Avatar
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    Glass is pretty easy IMO. I definitely think it would have to be skin.

  5. #5
    Registered User Andyjaggy's Avatar
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    Car paint. Especially the metallic paint where you can see the little flecks of sparkles in it.

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    Valiant NewTeKnight Matt's Avatar
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    Although I seen example node flows, a car paint material shader would be awesome, especially if it was faaaaast! How about it NT?
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    Super Member Captain Obvious's Avatar
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    Glass is a piece of cake. Then again, I never render glass where I would need caustics, so... Heck, most of the time I don't even use refractions on it, and it still looks great.

    The worst materials to simulate are the ones with small details, like sparkles or small bumps or something, when viewed from a distance. The client goes "this surface is supposed to be sparkly!" and I go "it is, but since we're seeing it from half a kilometer away, the sparkles kind of blend together" and the client goes "make it sparkly!"

    Gah.
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  8. #8
    Pancakes! IMI's Avatar
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    Well I must be missing something then, because glass has always given me trouble.

    Dielectric, I haven't messed with much, as I'm just beginning to come to grips with the node editor.
    But I'm not talking about refraction, reflection and specularity - I was meaning more about the fact that your average glass that's seen any kind of use at all is littered with imperfections: smudges, tiny cracks, maybe air bubbles within.
    Rarely in real life do you see perfectly clear, clean glass.

    Here's another question though: If you had a prism and wanted to do a render where the light shining through it was casting a spectrum on a white surface, how would you go about it?
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  9. #9
    \\ is sparkling // Iain's Avatar
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    When I was tinkering with 9.2 beta, I tried to get a prism to disperse light properly using a luminous polgon with the dielectric material but I just couldn't get anywhere.

    There's a render in the Maxwell manual which shows this setup but I don't know if it's fudged (probably not).

    For me, realistic fabrics are difficult.
    Glass, as the Cap'n said, is easy if you're not going for those close up caustic overload shots VRay spits out.
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  10. #10
    Super Member Captain Obvious's Avatar
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    Quote Originally Posted by IMI
    But I'm not talking about refraction, reflection and specularity - I was meaning more about the fact that your average glass that's seen any kind of use at all is littered with imperfections: smudges, tiny cracks, maybe air bubbles within.
    Rarely in real life do you see perfectly clear, clean glass.
    Ahh, yes, that is quite hard, isn't it? Bubbles are easy enough (just model them), but getting realistic-looking smudges, cracks and scratches can be quite the challenge. I normally deal with glass from a hundred meters away on the side of a big building, so it's completely different.
    Are my spline guides showing?

  11. #11
    Valiant NewTeKnight Matt's Avatar
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    Quote Originally Posted by Captain Obvious
    The worst materials to simulate are the ones with small details, like sparkles or small bumps or something, when viewed from a distance. The client goes "this surface is supposed to be sparkly!" and I go "it is, but since we're seeing it from half a kilometer away, the sparkles kind of blend together" and the client goes "make it sparkly!" Gah.
    Copy cat, that's what I said!

    It's AA that wipes it out!
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  12. #12
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    Exactly what happens with my brushed steel surfaces. Nightmare trying to light it to make it look realistic and the AA wipes out any effect unless in extreme close up.

  13. #13
    Glass isn't that hard - you can even get 90% of the way to beaten glass with some good grunge maps.

    Skin's pretty hard. Skin for full heads/bodies is even harder because it's so dependent on convincing textures, which will generally be very model-specific. I haven't even tried - organics aren't my strong suit. At least, not yet.

    Car paint is pretty easy to do for distant shots. For close-ups it gets harder, but I think it's in the realm of LW's abilities. Just tonight, having seen this thread, I made a pretty decent metal flake surface, using IWF2 Nodal. (Download here.)

    Now, you know what's hard? Volumetric anisotropic surfaces like tiger's eye, or various decorative plastics I've seen. I've even seen it in certain gel substances like hand soaps. I'd like to see those done in LW!
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  14. #14
    Accursed 5 minute edit limit: slightly updated the metal flake material to include specularity.
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  15. #15
    Registered User Andyjaggy's Avatar
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    Looks like a cool material. I just recently discovered the IFW textures. Really cool stuff. I like the kitty

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