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Need an object to ignore IOR
Posted: 24 October 2015 04:00 PM   [ Ignore ]  
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Joined  2007-04-24

I have a snow globe I’m working on. The only challenge I have left is that the logo inside the globe is being refracted in a very weird way and I would actually like it to someone not be affected by the IOR. Is there any way to tell an object to NOT be affected by IOR while it’s sitting inside of a glass ball?

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Posted: 24 October 2015 06:21 PM   [ Ignore ]   [ # 1 ]  
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Hi Sean Cusson,

Would you mind to share a scene file with the Sphere and a dummy object inside.

I’m not really certain which value you have in mind, it is not limited to one only.

To my knowledge there is no exclusion only of this, but I need to see what you have to suggest anything.

How would it look like if the “snow” is refracted differently than the sign, which might interact (dynamic/Rigig Body) with each other?

All the best


IOR= Index Of Refraction

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Posted: 25 October 2015 12:13 AM   [ Ignore ]   [ # 2 ]  
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Here is my work-a-round ;o)

I can’t find a way to have objects in the same “glass/water-sphere” and some are refracted more than others. Imagine for a moment this option were given, three parts in a glass sphere would have no, a strong positive and one a strong negative value, that sounds to me like “Scotty— beam us three up”, only to arrive as a Kraken on board, with six arms and six legs, etc. In other words, the mix would be difficult to separate or even to adjust. ;o) Sorry about the weird example.

The simplest idea would be to take the object apart and render in sessions. Half-spheres front, logo, half-sphere back, masks, object buffer, comp etc. Well, sounds like a lot work and perhaps a little change and the whole thing needs to be done again. So: nope.
I thought as well of a sphere with a sphere hole in the middle which contains a little bit smaller sphere for the logo. Since I have no data about the logo size, I can’t really test this. The logic would be to work in the smaller sphere in a different way than on the outside. Again, not tested with the right size

My suggestion might be kind of complex on first sight, but is pretty simple once you read one time through.

The sphere should reflect in many ways, inside and outside, for that I have used the Sphere.mirror. Simple and with nearly no or little refraction. (yes, little—read on…)

The next sphere (called Sphere) has a ‘flat nose”, adjustable with the Correction Deformer, and here with the Falloff>Offset>Y [second value, currently at 118cm]. This flat nose looks always to the camera and does not reflect, but the refraction is lower in the center, where the nose is the most flat. So, the logo/icon is less distorted, but everything else, especially the “ring” around the logo is. This Sphere has a material with NO reflection, but with refraction, adjust to your liking.

You can move the camera, and all looks fine. Who can really say that the snow-particles are less refracted in the middle area? However, I dialed in a little bit of refraction here to soften the trasition and have a good feel anyway.  Keep the snow in the inner sphere, but perhaps you test both options.

The orange figure is the placeholder for the logo, the pale bluish cage used here as an indicator for the refraction.
I hope that will work for you.

All the best


https://www.amazon.com/clouddrive/share/49BdlaFvsHUYbGDFwagutUJ6iv4DMAWu6tZPcuUWWf?ref_=cd_ph_share_link_copy

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
https://www.youtube.com/user/DrSassiLA/playlists

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Posted: 25 October 2015 06:21 PM   [ Ignore ]   [ # 3 ]  
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Perhaps easier to use is the blend of Normal Maps. Compare the two images. I have “baked” a normal [Object] map with a sphere intact, and one with the sphere flat on one pole cap.

Blending the top one in or out changes the normal direction without a need to change the geometry at all for the final scene. For the baking, again, this is a work that needs to be done.

I have not repaired the pol-caps here, I would suggest to use a Hexahedron and UV mode each time. I left the bad pol-caps in, to showcase the problem, the star like artifact in the center is the result.)

I limited the Normal maps to 2K, but I would rather suggest to go higher and 2:1 aspect ratio [equirectangular], and the bake sphere must have the same geometry/ point-polygon based as the final one.

As it is a rather large file, even in 2k square (normal should be 32/bit float—> OpenEXR, never “.hdr” !!!) to work precisely, here is a download link: ~50MB
https://www.amazon.com/clouddrive/share/hak2TJxkrrjvCt91OiIAV1tkeG5nrgXh7uvOMKOjiWZ?ref_=cd_ph_share_link_copy

Enjoy

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
https://www.youtube.com/user/DrSassiLA/playlists

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