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Rendering with Arnold in CINEMA 4D using the C4DtoA plug-in.
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Strange HDRI appearance on glass material

8 REPLIES 8
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Message 1 of 9
Peter_Matthews
492 Views, 8 Replies

Strange HDRI appearance on glass material

Hi, I am trialling Arnold with C4d having been used to using Vray.... Can anyone shed any light on this, excuse the pun, I am seeing the HDRI image affect a portion of a glass object as per the image below.... the bottom of the object is displaying correctly

I have spent hours trying to solve this!


7054-screen-shot-2020-05-13-at-173116.png

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8 REPLIES 8
Message 2 of 9
lee_griggs
in reply to: Peter_Matthews

  1. How are you lighting the scene? (screengrab your scene).
  2. What else is in the scene?
  3. What is the shader network on your bottle?
  4. What is the grey noise on the bottle? (is that the issue)?
  5. Are your ray depth settings high enough?
  6. Can you upload a simplified scene?
Lee Griggs
Arnold rendering specialist
AUTODESK
Message 3 of 9

Many thanks for the response, @Lee Griggs.

Yes the noise covering the top 2/3 of the bottle is exactly my problem. I have played with all of those setting your suggest at some point but see now change in the render output.

One thing that has come to light is I have just saved the project with assets in readiness to show you and the file is suggestion there is a missing HDRI image '0839 Cloudy Dawn HDRI'. I have tried to locate this in my file and can't see that anywhere. Maybe this would help to know where this is and if it is this that is affecting the render.

I have then stripped everything out of the scene and it still seems to be behaving weirdly. I have attached this here for review.Glass Bottle HDRI Issue.zip

As I said, I am trialling Arnold with the view to move away form Vray and so far been super impressed with the speed and ease, until you feel like a complete amateur with what is probably a simple issue such as this.


Thank for your help in advance


Message 4 of 9
lee_griggs
in reply to: Peter_Matthews

I put the glass bottle in a new scene, assigned a new standard_surface (glass preset) and it renders fine with an Arnold sky. I guess it is something to do with your scene. I would just rebuild it as I did or delete half of the scene to try and identify what is causing it (probably easier to just rebuild from scratch).

7035-1589451610147.png

Lee Griggs
Arnold rendering specialist
AUTODESK
Message 5 of 9

Thanks for that Lee, really appreciate your input.

I'll start to rebuild and they may even answer the question along the way.

Message 6 of 9

I see you have a Background Object in your scene. Note, that transmission is not supported on a background image, because it does not have a defined distance from the camera. Should be fine with an Arnold Sky or skydome light.

Message 7 of 9

Thanks Peter, so where does the backplate sit?

Message 8 of 9

Well, I guess the question is what do you expect to see on the glass. The image has no depth information, so it will be a fake effect anyway. You can attach a Plane to the camera clipping plane with the image using camera projection for instance.

I wonder what controls does Vray have for this case? In older plugin versions we had a checkbox on the Background Object to see the background image through transmission as it was projected from the camera (e.g. no refraction), but it was removed in Arnold 5. I guess you can achieve something similar with the ray_switch shader.

Message 9 of 9

Thanks Peter, I appreciate it will be a fake effect.... What i'd be happy with is just seeing the image through the glass material and trying some HDRI to give some adequate reflections on the material.

I'll try the camera clipping method and see what that results in.

Thanks again....

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