Help please! This is very easy in Arnold, but I have to do this in VRay...

[onyxlee]

Hello, guys, I am trying to keep my workflow inside VRay, but I ran into something that I wasted tons of time to do in VRay, but got it done fairly easily in Arnold. Can you enlighten me how to properly set this up in VRay? That will save me tons of time in the post production. Thank you.

So, what I need to do in Arnold is: on a sphere where it's perpendicular to the camera, the IOR is a certain number. Where it's parallel to the camera, the IOR =1.
So the first Arnold texture will give you a value between [0,1], at a spot where it's facing the camera, it's 1. The second node will map this [0,1] to [1,100], then feed to IOR. In the "facing ratio" texture, there are also bias and gain that are extremely important and convenient for the final result.


So, I tried to set this up using only VRay materials. It starts with a falloff (type: perpendicular/parallel), it will generate a value between [0,1]. Then I put a vraycolor there, set its RGB multiplier to a number like 100. then a VRayCompTex will multiply A*B. Then another VRayColor (RGB multiplier =1 ) and VRayCompText add (A+B) will finally bring the value to [1,101], which gives a somewhat similar result.



But the thing is, without bias and gain settings from Arnold, I have to try my best to adjust them in the falloff node and add more VRayCompTex, and the result is far from ideal. So I wonder, is there any useful tool, node, texture that I can utilize so that I can still have everything inside VRay? Arnold is really not my strong suit.

Thank you so much!

[^Lele^]

I'd think a CC node should do the trick.
Can you share the setup you're looking for, and that is too laborious to achieve right now?

[onyxlee]

I'd think a CC node should do the trick.
Can you share the setup you're looking for, and that is too laborious to achieve right now?

Thanks, Lele, what is a CC node short for?

Here is my arnold scene. Thank you so much!

Arnold Variable IOR.zip

[sirio76]

Color Correction

[^Lele^]

We do have a remap texturemap buried into the vraypluginnodetex: see attached.
If you mouseover the various spinners, you'll see a tooltip with their description.
You should only need the first part of the UI (up to and including "output max"), and of that only the leftmost spinners (i.e. no mapping of the values, no touching the blending with the map.).

As a side note: i'm not sure any current commercial renderer can do what you're looking for: the max IoR will be capped at some human-experienceable value, and a Black Hole, if small enough (i.e. not a supermassive one), will have an insane gravitational lensing at the event horizon, with stuff appearing echoed even three or four times over (meaning light was bent around for three or four laps...).
Cfr. this paper, f.e..

The fact that light rays can wind an arbitrary number of times around a black hole before emerging back toward spatial infinity has been well known since the earliest studies of general relativity [...] In practice, a source behind a black hole produces not only the two classical weak-field gravitational lensing images but also an infinite number of strong-field images corresponding to photons with winding numbers running from 1 to infinity

Alas, i'll be curious to see the results!