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I've used several Glass setups in the past. Since Version 4.1 none of them seem to work for my Windows. The Object always throws a complete shadow, even when the glass is mixed with a transparent shadow (light path). Any Ideas?

With window With window

Window hidden Hidden window

Same scene in Blender 3.6 Blender 3.6

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    $\begingroup$ since you nearly showed us no technical information/settings you made, i would recommend providing your blend file so we can check it out. $\endgroup$
    – Chris
    Commented Apr 10 at 12:26
  • $\begingroup$ I have added a blend file without sofa and hdri (too big) $\endgroup$
    – Dario
    Commented Apr 10 at 12:58
  • $\begingroup$ Apart from other problems (see the answer by @JagJB below), the setup you show in the screenshot will make the window transparent for the camera, but not the light source. So you should swap the inputs in the Mix Shader. $\endgroup$
    – Gordon Brinkmann
    Commented Apr 10 at 14:37

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Checking your file, I noticed that the 'Transparent shadow' option was not ticked in the material property.

Additionnally, you can add the node setup below to have more transparency in shadows:

enter image description here

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    $\begingroup$ Wow... I used that window for years now and never hat a problem. Maybe Blender 4.1 changes this tickbox?! Thanks anyways!!! $\endgroup$
    – Dario
    Commented Apr 10 at 14:39
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    $\begingroup$ @Dario & Jag JB: I would not use the Is Camera Ray light path here. If you do, the window becomes invisible for the camera. Not a big problem in this example scene with the empty white room, but when you the sofa back in there you will not see any reflection in the window. Using Is Shadow Ray is sufficient for the setup. $\endgroup$
    – Gordon Brinkmann
    Commented Apr 10 at 14:45
  • $\begingroup$ I wouldn't use it either personnally but assumed that Dario wanted a transparent window for the camera. If not, of course, remove that node. $\endgroup$
    – Jag JB
    Commented Apr 10 at 14:47
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    $\begingroup$ @JagJB Yeah, all fine, no offense. That was just additional information mainly for Dario because I assumed he might not be aware of that. Without throwing shadows or reflections, the simplest way would be to just delete the window 😉 $\endgroup$
    – Gordon Brinkmann
    Commented Apr 10 at 15:58
  • $\begingroup$ No offense taken ;) $\endgroup$
    – Jag JB
    Commented Apr 11 at 9:27
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Another possibility instead of using the custom made "Chocofur Glass Basic" nodegroup:

If you create a new material using a simple Principled BSDF there with a Transmission > Weight set to 1, light comes through the window:

basic glass

But admittedly it was always problematic that simple glass materials like using only the Glass BSDF or the Principled BSDF with Transmission enabled is scattering the light a lot so that even small light sources do not produce really sharp shadows.

As a workaround to change that you can use a Light Path node, invert the output of the Is Shadow Ray socket and plug it into the Alpha input of the Principled BSDF, for a Glass BSDF you would have to mix it with a Transparent BSDF (but inverting the output would not be necessary as you could simply swap the inputs in a Mix Shader).

is shadow ray

This setup not only sharpens the shadows but also lets more light inside. So depending on your lights/environments you might have to reduce the strength of light sources or the exposure.

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