Ghost Lights are back in the new Beta 4.21.1.26.

Instructions:

https://www.daz3d.com/forums/discussion/609556/creating-a-ghost-light-daz-studio-4-21-1-25%C2%A0

Working link:

https://www.daz3d.com/forums/discussion/609556/creating-a-ghost-light-daz-studio-4-21-1-25%C2%A0

Oh hell yeah!

Thing is, I changed all my ghost light light luminosity values to be one million times higher to get the same effect after the last update and now I will have to change them back when the ghost lights in beta become live... oh well...

The existing lights won't change, for good or ill, due to the new system. It is using a totally different approach.

As Richard has said, there is a different way to to get them to work, you'll need to read the forum page and download the scripts at the link I posted. Of course you can carry on with huge luminence values if you so wish.

I'll just go with my gigantic luminance values for now

This guy has written about it:

https://levicki.net/articles/2022/12/25/Ghostlight_support_in_Daz_Studio_421126_and_above.php

He has also written a script (it's in the Downloads section) to turn a simple geometry node (i.e. a 2D plane, etc) or an existing render emitter (i.e. built-in light source) into a ghostlight with one click.

Bear in mind that the ghostlight functionality is experimental (read: buggy) at the moment so any weirdness should not be blamed on the script which works just fine but on the Daz Studio and Iray.

Cobbler3D posted at 3:11 AM Mon, 26 December 2022 - #4452512

Oh hell yeah!

Thing is, I changed all my ghost light light luminosity values to be one million times higher to get the same effect after the last update and now I will have to change them back when the ghost lights in beta become live... oh well...

With this latest Iray change they can again be fully invisible without using opacity trick at all, and without having to use insane luminosity values. You can even have them be visible on some glossy surfaces but not on others (Ghost Light Factor property can be set on both light emitting and receiving surfaces).

Can anyone confirm whether or not that the latest DS (as of this writing 4.24) supports invisible emissives (ghost lights) as supported in DS version 4.16.0.3 or earlier? For example, in 4.16.0.3, if I set emissive Cutout Opacity=0.000001, then I get transparent geometry that still emits the same as it I set the opacity to 1.0. I use this type of invisible emissive on virtually all of my renders and I have been very reluctant to upgrade DS for two reasons: 1. I don't want residual shadows from emissives plusI don't want reflective surfaces to reflect the geometry,  2. I hope to re-use my existing project files (they go back to the first days of Iray in DS) seamlessly with the current version of DS.  

Thanks for any information you can provide.

Can anyone confirm whether or not that the latest DS (as of this writing 4.24) supports invisible emissives (ghost lights) as supported in DS version 4.16.0.3 or earlier? For example, in 4.16.0.3, if I set emissive Cutout Opacity=0.000001, then I get transparent geometry that still emits the same as it I set the opacity to 1.0. I use this type of invisible emissive on virtually all of my renders and I have been very reluctant to upgrade DS for two reasons: 1. I don't want residual shadows from emissives plusI don't want reflective surfaces to reflect the geometry,  2. I hope to re-use my existing project files (they go back to the first days of Iray in DS) seamlessly with the current version of DS.  

Thanks for any information you can provide.

That was a bug, nVidia fixed it and it will not revert. We now have the alternative system using advanced node properties which was introduced to restore a form of ghost light, and that still works.

So, Richard, I assume you mean that it was originally a library defect (going back at least to the beginning of Iray in DS), and nVidia refuses to implement a change that would accommodate those who were using that as a feature.  I need to upgrade and would appreciate advise as to the the quickest and most efficient method for converting transparent emissives that use the Cutout Opacity=0.000001 method. I use one to light faces (an approach I purchased from a vendor here on Renderosity).  It sits right in front of character head in most every scene. 

Initially, after the DS version following 4.16.0.3, my testing showed a flaw in the conversion method offered then.  The object was visible on reflective surfaces (e.g. any shot that included character head in a mirror). Has this been addressed?

Fortunately, I have, for the most part, opted to change the size (for some reason) of the object instead of changing the opacity, so, if I can zero in on creating a 1-2 click preset method, I might be able to convert with a minimum of disruption to my work flow. Thank you for any help you can provide.

Making the source invisible in relfections is where the Ghost Light factor comes in - set it to 1 to hide reflections in very shiny surfaces, higher values for rougher surfaces. https://www.daz3d.com/forums/discussion/609556/creating-a-ghost-light-daz-studio-4-21-1-26