So, when I increase IOR it causes objects on the other side of the glass to magnify. When I used to use 3ds max/Vray, you’d have two IORs (one for reflection, one for refraction).
I want a higher Index of reflextion to enhance window reflections. In max, you’d then up your IOReflection to whatever you want and then change IORefraction to 1.0 to stop the weird warping effect.
Any ideas how to control this in Blender?
Answer… you have to add a solidify modifier to the glass. Mine was just a 2d plane.
This is a much better setup for architectural glass used in windows. Works for single faced glass, and provides (fake) “fresnel” shadows, without any issues coming from refraction which is part of normal glass:
I’ve seen @CarlG’s node setup used before to cheat to get around some of the limitations of the physically-accurate Cycles and Glass BSDF implementation.
But, changing the IOR in the Principled Shader or Glass BSDF, is equivalent to telling the renderer that you are no longer using regular glass that would be found in a window and it is now something exotic like crystalline iodine, gallium, or silicon.
If you want a brighter reflection, you will probably have to increase the brightness of your interior lights.
If you want to stick with a physically-accurate glass IOR value, you may get better convergence by using Light Portals: https://docs.blender.org/manual/en/latest/render/cycles/light_settings.html#light-portals
FresnelVsPower is so close it doesn’t have any implications to reflection values at all:
I just meant that the approximation is just that - it doesn’t include refraction. If physical accuracy is important, @wonderland78 could still use the Glass BSDF with accurate reflection and refraction and the render could still probably benefit from using Light Portals. I’m not sure where the where the requirement for the openings to be small comes from. The manual says:
Area lights can also function as light portals to help sample the environment light, and significantly reduce noise in interior scenes. Note that rendering with portals is usually slower, but as it converges more quickly, less samples are required.
Light portals work by enabling the Portal option, and placing areas lights in windows, door openings, and any place where light will enter the interior.
I suppose there has to be a tipping point where the use of Light Portals is no longer beneficial - else there would be a recommendation to use them all the time. I mean, in the manual, the very next sentence says:
In outdoor scenes most rays do not bounce much and just fly off into the sky and therefore, light portals are not helpful for outdoor scenes.
There is no refraction you want on a single plane as he initially used; the refraction you get will be infinite (causing the bending artifact he mentions) that can be avoided using geometry/incoming normal (only for the refraction part, not the glossy part, so you have to set it up manually to get this access).
On a solid panel of glass, there will be refraction, but because the two faces are close together and parallel you won’t notice it at all in a static shot and very hard to spot in a moving shot. This is true for windows which are surrounded by a window frame and wall.
If you can see the edge of the glass (not fully framed, like an indoor glass fence) I would go full glass and volume absorption (for the edge tint due total internal reflection) and setup the shadow handling independently. This because now the refraction can be visible, as it shifts the appearance in the glass from the background surrounding it.
The difference between thin glass with geometry/incoming based normal and and transparency based with real (more complex to setup) fresnel is none.
The difference between thin glass with geometry/incoming based normal and and transparency based with approximated fresnel is not observable.
The difference between solid glass and transparency based glass is that the secondary (internal) reflection in transparency glass is farther apart and not reduced in strength.
Transparency based with approximated fresnel for framed wall windows, single pane.
Transparency based with approximated fresnel for framed internal doors, double pane.
Real glass/absorption with fresnel shadow handling for internal non framed fences, double pane.
Light portals guide the rays to find the environment light. When a ray bounces of a wall, instead of going to some random location and maybe find the environment, the light portal tells the ray “try this direction” and you’ll find light. You’d use it on any small opening, regardless if you have a glassed window or just an opening.
The downside of using refraction is that refraction is opaque to light rays and cause a solid shadow if not relying on caustics. And the white transparent shadow “fix” many use is not strictly correct, it should utilize fresnel as well, which is further complicated by how fresnel is normal dependent (for total internal reflection) and need solid geometry to work (to terminate the refraction).
The glass shader needs two switches;
Architectural - which replaces caustics based shadows with fresnel transparency based.
Single Sided - tells the shader to use incoming normal for the refraction part. Both sides become “front”.
And possibly separate roughness.
