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I'm wrapping up an original concept car I made for practice and struggling with this glass shader on the windshield (shading is one of my weaknesses). I'm using this setup (the ramp isn't necessary to reproduce the effect): enter image description here As you can see below, it produces an infinitely repeating pattern of whatever it is reflecting—restricted by the number of max glossy bounces. Curiously, it does the same thing in UE5 even when I use a basic glass shader. enter image description here I'm interested in finding a solution, but even more interested in understanding why this is happening so I can use that knowledge to be a better artist. Thanks in advance for any help! <3

Using v3.3.0, but I expect this is repeatable with any version.

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    $\begingroup$ Does your windshield model have a thickness, have you modeled everything in scale, and do you have anything inside the car to actually see through the windshield? $\endgroup$
    – L0Lock
    Nov 11, 2022 at 1:00
  • $\begingroup$ @L0Lock Yeah, everything is modeled to scale. Glass has realistic thickness. Scales are applied. All that good stuff. This is repeatable with two fresh primitives and the shader setup pictured in my post. $\endgroup$
    – Max Williams
    Nov 11, 2022 at 2:34
  • $\begingroup$ I'm not sure to understand the problem. I can't understand the render screenshot as well. Can you indicate me where exactly I should look at to see those infinite reflections? $\endgroup$
    – mqbaka mqbaka
    Nov 11, 2022 at 8:58
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    $\begingroup$ You shouldn't mix transparency and transmission. Exchange the glass shader with a glossy shader and adjust your colorramp to the new situation. $\endgroup$
    – Frederik Steinmetz
    Nov 11, 2022 at 10:04
  • $\begingroup$ @FrederikSteinmetz That was it! Thank you so much. Is this because the glass shader already has a glossy shader inside of it or something? So it's just kind of duplicating the same effect? $\endgroup$
    – Max Williams
    Nov 11, 2022 at 15:26

1 Answer 1

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It seems due to the combination of glass and transparent and Fresnel.

If you change one of these 3, it looks better. See for example below a combination of Transparent and Glossy, or the use of a Layer weight instead of a Fresnel.

enter image description here enter image description here enter image description here

EDIT : changing the thickness also works enter image description here

and adding a light path node allows to control the number of reflections. enter image description here

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  • $\begingroup$ That appears to do the trick! Idk why I didn't think of that. Shaders clearly aren't my specialty haha. Thanks! I'm looking at it more now and it looks sooo much better. Wow. Cheers. $\endgroup$
    – Max Williams
    Nov 11, 2022 at 15:24
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    $\begingroup$ Actually, that doesn't seem to have resolved the issue. It still happens. It's just less noticeable. If I just use a glass node, that works just fine. If anyone can tell me what's going on here, I'd really appreciate it. I think I'll just stick to the glass node. $\endgroup$
    – Max Williams
    Nov 11, 2022 at 17:40
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    $\begingroup$ It seems that infinite reflections are a normal behaviour in thick glass. Nevertheless the reflection should be darker and darker one after another. See the physical explanation here : physicsmax.com/wp-content/uploads/2014/08/1359.jpg I also added another way to fix it : by reducing the glass thickness. Therefore the successive reflections are les noticeable. $\endgroup$
    – Jag JB
    Nov 11, 2022 at 23:09
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    $\begingroup$ With a lightpath node setup, the number of reflections can be adjusted if too many are not desired. I edited the answer accordingly. $\endgroup$
    – Jag JB
    Nov 11, 2022 at 23:19
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    $\begingroup$ Ah! Okay. That makes sense. Thanks for the explanation, link, and updated answer <3 $\endgroup$
    – Max Williams
    Nov 29, 2022 at 19:50

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