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Thread: Checkerboard pattern on Glass and Paint materials

  1. #1
    Senior Member JohnG's Avatar
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    Checkerboard pattern on Glass and Paint materials

    I've installed the hot fix for 2012.5 but the checkerboard pattern is still an issue with the glass and paint materials although not with the plastic as far as I can see.
    I wasn't able to watch the webinar on Thursday because of work so maybe this issue was mentioned, I've posted some renders below to illustrate the problem.

    What's strange is that the pattern almost disappears but then reappears as the render progresses


    Glass_Test_500.jpg

    Glass_Test_1000.jpg

    Glass_Test_1500.jpg

  2. #2
    Senior Member haknslash's Avatar
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    Same here
    Kenny Wilson
    900D ASUS Maximus VI Extreme 4770k 3x GTX 780 Ti's AX1200i 32GB RAM H100i a lot of SP120 fans
    Bunkspeed Shot Pro 2014

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    Senior Member andy's Avatar
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    Actually, if you watch it in real-time (not background render) you'll see the checkerboard appear and go away many many times. This happens in Max as well. But I think Max is still on iRay 2.1
    As far as I know, that's normal iRay behavior. I was Going to show an article from the iRay dev blog, but I frequently have troubles with that site for some reason. Anyway, I know they've said something about it in the past.

    Edit: It's loading now. Unfortunately the "fix" isn't great.
    dev blog direct link

    It's improved, but still happens. It seems the way to avoid it is to add some noise. It can be subtle, but that also means you will require some extra texture mapping on what would normally be a smooth surface.
    Last edited by andy; 08-20-2012 at 05:53 PM.

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    Senior Member JohnG's Avatar
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    This is definitely not normal iRay behaviour Andy. This is something that has appeared in the last update, previously glass always cleared very quickly with no checkerboard pattern. Looking at renders done in previous versions I don't see any of these artifacts.

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    Senior Member blitz's Avatar
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    I found those checkerboard patterns to take a long time to clear when using physical lights even in iray 2.x. I also noticed it would appear, dissappear and reappear repeatedly as they do now with iray 3.0. The checkerboard pattern became less and less prominent as time progressed. However I do believe John is right in that they are more visible now and this might be due to the lack or change of image filtering in bunkspeed 2012.5.
    Last edited by blitz; 08-20-2012 at 06:11 PM.

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    Senior Member andy's Avatar
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    Since I've always seen that at some point in my scenes I found it normal. I know it's usually worse with transparent and glossy surfaces, which is why you may not see it in plastic material. It's difficult to tell how bad it is with only 3 screen grabs.

    I tested it out with solid glass, I created the material and didn't use a preset, on a default sphere with roughness 15 and thickness 100 with the color on the whiter end of things. The environment is the default and I just took the default camera, changed it to square and framed the sphere.
    The pattern shows up at about 100 frames and becomes continually more defined until probably 500. It's hard to know where it starts getting better, but at 750 it's Definitely noticeable. And similar to yours, by 1000 it's pretty much gone. There's still some tiny ones left in the brighter areas, but it'd be usable.
    The difference is with my test I just passed 1600 and it hasn't gotten any worse. There are some small zippers left that don't seem to be changing at all though. After 2500 I'm giving up and saying it's got to be related to a specific material. My image isn't changing anymore.

    Post up your settings and I'll copy them and give it another try.

  7. #7
    Senior Member JohnG's Avatar
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    Just to be clear (no pun intended) I'm not saying I've never seen this type of checkerboard pattern in previous versions, I have, (usually on matte or glossy surfaces) I've just never seen it like this on glass and the fact that it reappears as the render progresses is weird, I don't think I've seen that before.

    I remember reading that tip about adding a noise map to help disguise the pattern. It would probably be a good idea on a matte or textured surface but not so good on glass.

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    Senior Member JohnG's Avatar
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    Quote Originally Posted by andy View Post

    Post up your settings and I'll copy them and give it another try.

    I just created a sphere primitive in Move and applied the standard solid glass material from the library and used the default environment.

    The reason I know something has changed is because the project I was working on before I applied the 2012.5 update was a series of renders of a DVD case, I was using the window glass material on the outer sleeve of the DVD case with a texture underneath. I had a nice reflection across the top right corner of the DVD case from an emissive, it looked fine and rendered very quickly.
    Then when I applied the update I get this very obvious patterning across the glass surface and had to let it render much longer to get it too clear.

  9. #9
    Senior Member andy's Avatar
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    You'd be surprised. I've done it there before as well. If you need a value of 212 for your glass, just create your noise with that color as a base. You'd only use about 2% noise. And at that transparency it won't be visible. The trick is to make sure the texture, on your object, is small enough that it is the same size as the noise in your image, or smaller. Unless you're doing 40 hour renders, there should be at least a small amount of variation. People just don't seem to like the word noise.
    I actually end up creating noise intentionally when I plan on printing. If you don't do that, you'll see banding. Noise eliminates banding. So there's definitely a happy place in the middle. You need noise, but you don't want to see it. It's the same thing in this case.

  10. #10
    Senior Member andy's Avatar
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    Ah, default glass. Actually I wasn't getting Any. I let it go to 2000 and zippering never showed up. Does it still happen if you don't use a preset material?
    I tend to not use preset materials because I don't know how they are defined. In other software I've used in the past, vray was the worst, we actually had crashes from reusing materials. My coworker didn't believe me so I recreated the exact same materials with brand new materials and applied them to the same objects. I then removed the old materials from the scene. No more crash.

    After that I stopped using presets, or if I used a preset, then had any issue, I created a new material completely. I'm not saying that is the case, but it's worth a try.

    If you used hypershot back in the day, you might remember a few materials that could be created by bunkspeed that you couldn't modify, and couldn't create? I wonder if there are hidden settings we don't have access too, but can be changed. Those settings might be changed in newer versions of the software, but most companies won't go back and update all the materials they've ever created with the newer shader model. Maybe Bunkspeed will comment on that to see if it's the case.

    The other thing you mentioned was emissives. Remember those have changed as well. Also, with larger lights, even emissive ones, you get less zippering. What happens if you move your light much further from your product and make it larger to match?

    Unfortunately, as the renderer changes, some of the things that make it more efficient, or higher quality, etc, will actually break our old scenes. Open up an old hypershot file. Shot is a completely different software now, so yeah, it looks different. As we get updates to iRay, a little of that may happen. So we might have to move lights around, and adjust material colors to match.

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