Dark Surfaces on Glass Material

# 1 27-10-2013 , 12:01 PM

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Hi, I’m fairly new to maya and I’m having difficulty rendering a transparent object. Many surfaces of the material are very very dark in the render.

I’m modeling a cd jewel case. At the moment I only have the bottom part of the case which is completely transparent. However each time I render the scene many of the surfaces are far too dark, in fact they are almost black. I’ve placed the case on a white surface and am lost for ideas as to how to make the transparency of the object more realistic. In real life the are no black areas on the cd case.

If anyone has any ideas I’d be very grateful!!

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# 2 27-10-2013 , 04:45 PM

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- What kind of shader are you using? And can you show a screenshot of the settings?
- What are your raytrace render settings?
- Is the scene sitting in black 3D space?

- Genny
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# 3 28-10-2013 , 03:15 PM

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Perhap change the material, the light, the geometry. Really there are a number of things that can fix it, but you need to give more info on the scene for any of our advice to be effective. Please supply more information and we can help you a whole lot more. Thankyou for cooperating, and I hope we can fix your issue soon enough. Although with what you have given now the most we can do is throw guesses and ideas at you about what is wrong.

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# 4 29-10-2013 , 10:09 AM

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Ok so apologies, I really had no idea where to start with knowing what information to give, here’s a full breakdown and again if I’ve missed anything important please let me know?

Geometry

The geometry of the scene is very simple, there are two visible objects, the plastic cd case (which I’ve referred to as glass as a glass type object is perfect for what I’m trying to achieve) and a flat plane that the cd case resides on.

The flat plain is a white lambert which colour set to pure white and no reflectivity. The cd case is a phong e with the following attributes:

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Lights

There are three lights in this scene, the main light over your right shoulder (if you are looking through the camera) is a point light aimed at the cd case:

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The second light is intended to light the darker areas on the left and is over your left shoulder, settings are similar although it is less intense and does no cast shadows.

The third light is off to the distance in the far right, only emits specular and does not cast shadows.

Render Settings

I’m using mental ray to render the scene, here are the settings:

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# 5 29-10-2013 , 10:53 AM

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You probably need an environment sphere to give reflections. It could be that it is just reflecting the black space around, as Genny suggested. Create a sphere with some kind of texture and set it to not cast or receive shadows.

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# 6 29-10-2013 , 12:15 PM

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The environment sphere has made a massive difference, seems so obvious to me now that it’s been pointed out that you would need some sort of environment for the scene to work, thanks for the help.

Here’s the scene now, you can see there is a remarkable difference. However, there are still some very dark areas which are unrealistic compared with how the case appears on my desk in front of me. Does anyone have any ideas how this can be improved further?

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# 7 29-10-2013 , 11:53 PM

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You could try increasing the refraction limit in the shader's raytrace settings. Or you could use the mia_materialx, it has presets that can be tweaked. I remember a few versions ago, even the mia material had an issue with this, where after the set amount of traces the surface would go black, now you have the option to use the environment or a custom color.

- Genny
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Dark Surfaces on Glass Material

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