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01-06-2014, 10:40 PM   #1
JustMcCollum
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Wine Glass rendering issues in Mental Ray?
Hello. I'm trying to render a wine glass in Maya that I plan on exploding using Pulldownit and Realflow.

I modeled the wine glass by using a picture of a real wine glass on an image plane and revolving a NURBS curve into a polygon-made glass.

I've been using Maya for 4 years now, and I still can't figure out what's going on. I own Maya 2011 and this is a snapshot of the problem with my wine glass..



I have tried using both the dialectic and Mia_Material_X mental ray materials, but the image above is using the Mia_Material_X with the "Thick Glass" preset, with some modifications.

The issue is the inside of the glass and the wine inside the glass appears to be too distant, you know what I mean?

But look at the X-Ray of my wine glass...



It is the average thickness of a wine glass and the wine inside is very close to the edge like it should be.

I also have the scene scaled to the right size, which is important with lighting and mental ray. The size of my wine glass is 18.62 cm in height, which is equivalent to a 9-inch tall wine glass. I am using Image-based lighting, because I have gotten some pretty realistic results from my other projects in the past using it.

Here are the settings for my Mia_Material_X.



If I select "Thin Walled" under Advanced Refraction or select the "Thin Glass" preset, this is what I get...



The glass becomes WAY too transparent, it loses pretty much all the reflections, and it doesn't give me the shadows and highlights of the thick glass preset, which I liked. BUT you can see that's how the wine inside should be placed. Even with the "Thin Walled" setting enabled, I tried playing around with "Max Distance" and the reflection and refraction settings, and nothing changes the way I want it to.

This is it with a dielectric material...



What could be the source of the problem, causing the inside of the glass to be smaller and distant?

I don't think it's the geometry itself, because I modeled it exactly as the reference image I used. Does it have to do with the image-based lighting? Is it something in the mental ray settings? The material itself?

Any help would be greatly appreciated. I fiddled around with this all day and I can't figure out what the problem is!

What should I do? Thank you.

Last edited by JustMcCollum; 01-06-2014 at 11:19 PM.
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01-06-2014, 11:41 PM   #2
JustMcCollum
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NEVERMIND! I figured out what the problem is! It's the Image-Based Lighting HDRI Map I've been using! The way the lights are being casted in the HDRI file is bouncing off the geometry, makes the inside look more distant. But playing around with other HDRI Maps, I've gotten a lot better results! Thank you anyways!
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02-06-2014, 12:39 AM   #3
Gen
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It looks like the normals on the geometry are facing the wrong way to be honest. I think the glass is modeled to be pretty thin, perhaps too thin to be realistic.
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02-06-2014, 12:59 PM   #4
JustMcCollum
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Quote:
It looks like the normals on the geometry are facing the wrong way to be honest. I think the glass is modeled to be pretty thin, perhaps too thin to be realistic.
Thank you for your critique, and you're right, the walls of the inner glass were too thin. But I pulled them in a little bit, and created a glass material using a Blinn shader. To me, it looks so much better now! But my new issue now is maintaining the reflections, but getting rid of the reflections of the stem and the foot off the bottom of the bowl of the glass.



What do you think?

Last edited by JustMcCollum; 02-06-2014 at 01:04 PM.
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03-06-2014, 01:03 AM   #5
Gen
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Actually I think the reflection is normal. If anything, the air gap issue should be addressed. You can go the route detailed in the help docs or you can try Puppet's dielectric interface shader from his shader pack.

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