Glass Bump Issue - How to fix?

[Suthriel]

@Tim_Hobson

If you want to use Refraction with Ray Tracing for translucent materials, use the Specular value to drive the refraction amount.

I’ve got an example comparison in the docs here: https://docs.unrealengine.com/en-US/…dditionalnotes

I have to say, i am really confused by this statement, because i was always under the impression, that specular is the amount of light, that gets reflected with (almost) the same angle, that it hits the surface, and refraction determines the angle, at which light/a ray travels trough a transparent medium. And that angle changes, if both have a different IOR (f.e air = 1.0, water = 1.33).
So you might check that again, because it´s true, that both reflection and refraction are calculated with IOR, but they have completely different effects, and the specular should not affect refraction aka light bending (that´s what we are currently after).
And i wonder, why should we even bother with a specular value, if we using the metallic workflow, where only metallic ( for zero = non-metallic mats like plastic, and 1 = metallic like copper and iron etc) and roughness matter, as far as i know, and specular is left untouched.

https://upload.wikimedia.org/wikipedia/commons/b/bd/Lambert2.gif

Source: Diffuse reflection - Wikipedia

https://physicsabout.com/wp-content/uploads/2018/06/reflection-and-refraction-of-light-min.png

However, after that hint about specular and IOR, i found this in one of the Blender Forums:

The official Blender documentation provides a method to get the “Specular” value for the PBR-material reflections if the “IOR” value is known. To get the “Specular” value from the “IOR” value, we can use the following equation:

https://b3d.interplanety.org/wp-content/upload_content/2019/08/03-3.jpg

It is not difficult to create it with nodes

https://b3d.interplanety.org/wp-content/upload_content/2019/08/01-7.jpg

It should be noted that this equation is valid only for dielectric materials. For its proper work you must specify real IOR values, for example:

• water IOR = 1.33
• glass IOR = 1.50
• diamond IOR = 2.417

https://b3d.interplanety.org/en/get-…ions-from-ior/

Also, this here might be interesting for someone:

http://guerillarender.com/forum/viewtopic.php?id=767

http://i.imgur.com/7EgLI4Q.jpg

http://i.imgur.com/rR05wJE.jpg

http://i.imgur.com/WzA25GG.jpg

And this site too: https://refractiveindex.info/

Especially it´s Reflectance calculator ^.^

@BernhardRieder : To clear up some confusion, IOR values can be over 1, but the inputs in those materials usually just accept values from 0 to 1, representing 0% to 100%. So usually we have to calculate from the IOR or whatever else you have in mind and translate this to a zero to 100% value or gradient. That calculation is in our case usually done by the Fresnel node, which already outputs a greyscale value/gradient between black and white, zero and 100% or 0 and 1.

Edit: something really makes no sense here, raster and raytracer react differently to IOR-Refraction and specular values, check the rasterized material preview and whats happening in the RTX scene in the background. Did someone at Epic got confused abouth refraction and reflection and hooked something to the wrong input in the Raytracer?

Refraction Reflection

And i still miss the always mentioned Absorption for RTX How can we access absorption?