refraction issues with mia_x_passes material

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  09 September 2009
refraction issues with mia_x_passes material

guys i am rendering a bottle half full of water.

The reflections and refractions in the top part of the bottle where there is no liquid is fine however where the water is the refraction is incorrect. In real life the refraction is reversed, the image appearing back to front or upside down depending on viewing angle, yet i am not able to recreate this in maya?

I have tried adjusting the refractions and reflection levels in the render globals, tried adjusting all the settings inside the shader and now i am at a complete loss.

Any suggestions?
  09 September 2009
Is this a bottle you have modelled based on a photo of the effect? A photo compared to a render might help diagnose the issue.

Not to patronize but the resulting refraction is based on the shape on the 'lens' and the refractive index of the material. Changing the settings in the render globals will have no effect, since this just controls the depth of the raytracing and if you can see something through your refractive object the trace is likely fine.

How many surfaces are there in your bottle? - often people take the inner surface of the bottle, separate it and assign the liquid material. You may also have to play around with the direction of the normals.
  09 September 2009
Hey guys.I've attached a scene,with this effect on,hope it'll be helpful
  09 September 2009
dude that is exactly the result i am aiming for, different refractions based on whether there is air or liquid.

I have set up my bottle already with three materials, one on the outside surface, one on the inside surface for the liquid and one on the liquid top. Normals are based as shown in picture so basically it is based on what is suggested in the maya help.

As you can see from the two renders when it is just the inner surfaces the refraction varies based upon the water and air, yet it is not reversed.

When i add in the outer surfaces, the refraction becomes reversed everywhere despite it only occuring through the liquid in real life, and there is no difference now between the refractive level.

This is what is confusing me.
  09 September 2009
Hmm is the detail on the outer surface a bump map or displacement? I can't think why that effect is happening. How thick in world units is the glass?
  09 September 2009
hey man,

firstly thanks for your help with this.

The detailing is just done with a bump map though it is projected. Doesn't make any difference if it isnt there though.

The distance between the outer surface and inner surface (no matter whether it is vodka or air) is 0.233 units. I've also tried scaling up and scaling down the entire scene, still the same result.

My head is getting sore form banging it on the monitor too much
  09 September 2009
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