4.20 Flag a surface as a ghostlight
Granville
Posts: 696
Here is a quote from the 4.20 announcement page https://blog.daz3d.com/daz-studio-4-20-volumetric-clouds-smoke-and-fire-effects/
A fully supported ghost light solution. Ghost lights used to be dependent on bugs in Iray and would stop working when those bugs got fixed. However, this release provides ways to create lights and flag them to have fully supported ghost lights that will keep working even as Iray is updated.
Question: How do you flag a surface as a ghostlight? I can't find it in the surfaces tab. Any Idea?
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In that weeks-old statement, Daz touts "A fully supported ghost light solution". I have never seen any official Daz statement on what that "fully supported ghost light solution" is, or how to actually use it. I've only seen several different user-suggested things in the forum. Some people say divide the luminance by opacity. Some say we have to add a new parameter to the mesh to make it invisible to primary rays. Some say we have to add and enable Iray Matte. Some say we have to use refraction. Some say we need varying combinations of these things. When someone proposes a solution, someone else points out flaws in that solution. Daz just says nothing about how to use it.
Edit for spelling typos
Sooo, does that mean when they post these anouncements, they are just vaporware?
To me it means they spend a lot of effort adding things to Daz Studio that they never tell us how to use. Sometimes Richard Haseltine will post a link to something in the change log, but it is often difficult for average users to make any sense out of. The change log is certainly not any kind of step by step tutorial. You can find it here if you are so daring.
I think ibn this case it isn't beinfg claimed to be identical, but that what is there is now a feature and not an exploit - the matte and Visible to Primary Rays options from the advanced Iray node properties.
The version of "Create Advanced Iray Node Properties.dse" that I have in my Content Library Default Resources product, does not create the Iray Visible to Primary Rays property. I already installed the latest DIM update to Default Resources for DAZ Studio 4.20+ dated 2/17/2022. Where is the the version that creates the Iray Visible to Primary Rays property?
I don't think they updated the script for the latest Iray. It doesn't add the volume priority properties either.
Sorry, I keep getting muddled between what has been in the chnage log and what has been issued. You can see how to write a proeprty creation-script here http://docs.daz3d.com/doku.php/public/software/dazstudio/4/change_log_4_20_0_2#4_15_1_95 and indeed we have at least one such script from a user
I was under the impression that updates were planned, which is part of the reason I keep getting muddled. Of course "under the impression" isn't a guarantee of anything.
Request #406009 submitted to ask them to update Create Advanced Iray Node Properties to add the two new properties.
You can often see behind the curtain.
My "feature request" is probably an even lesser guarantee than your "under the impression".
I am told that there is an update planned which will, among other things, ad the new properties.
You can, of course, just add the properties listed in the chnage log without a script (which I think you have been doing) - however, this has shown up a bug in the Create New Property dialogue that prevents editing the of the Max value for Inet properties - it can still be done by creating the proerpty, then using the gear icon on the slider to open Parameter Settings. The bug has been fixed in an internal build.
Thanks for the news update!
Yes, I have been adding the property manually, but that is a pain to do on each object that needs it. I noticed the problem with entering a numeric value for the max limit. That value can also be changed with the slider in the new property dialog itself, without waiting to edit the property after it is created.
Back to the title of this discussion. So the blog is announcing something that's not in release yet. It will be implemented in a future beta, perhaps.
Then why DAZ doesn't fix the blog it's kinda misleading this way. To use kind words.
The features are there and working, it's only the script that makes it more convenient that is yet to come.
Richard stated it succinctly. I'm more long winded. This is the state of the Daz Studio 4.20 ghost light situation, as I understand it.
The BLOG statements about DS 4.20 providing a supported ghost light solution are literally accurate. The issue is that they didn't address the questions of "What is the supported ghost light solution?" and "How do I implement that solution?".
"What is the supported ghost light solution?": Richard Haseltine clarified that the new supported ghost light solution consists of using two advanced Iray properties called "Enable Iray Matte" and "Iray Visible to Primary Rays". Enable Iray Matte must be set to On and Iray Visible to Primary Rays must be set to Off. Setting these properties is what the BLOG refers to as flagging the lights. The lights to be flagged are mesh lights (geometry with emission turned on). All of this is implemented in DS 4.20. But how do you find it in Ds 4.20? That takes us to the next question.
"How do I implement that solution?": Daz Default Resources provides a script called Create Advanced Iray Node Properties. Select your mesh light in the scene and run the script. That will create the Enable Iray Matte property. You will fin it in the Parameters pane under Display>Rendering>Iray. It defaults to Off. Set it to On. Unfortunately, as of DS 4.20.0.11 Public Beta, Daz has not updated that script to create the other required property, Iray Visible to Primary Rays. To create that property, you can find a script by forum user jag11 in the forum Beta thread, or create it yourself based on comments in the Daz Change Log. Then you will find that property in the same place, Display>Rendering>Iray and set it to Off. Richard said that Daz plans to update the Create Advanced Iray Node Properties script in the future so it creates both required properties.
Well if "visible to primary rays" requires an external script to make it work then the blog is misleading, as I said before. One would expect the solution to be available in the release version, that isn't. Or they should explain it very clearly in the blog, possibly with a link to the required external script. The common user will never hunt the forum to get a feature it is stated to be there from the start.
Honestly, often and it's more often than what I find it normal, DAZ and the moderators, including Richard that I do respect immensely fot his nice work, are defensive to not credible limits when it comes to admit a failure in the DAZ actions. It is just a shame that more and more essential things are resolved by users and PAs instead of being resolved by DAZ.
But thank you @barbult for the nice explanation.
The features are available, the script (which is, in its present form, included with Default Resources) is to make life easier.
Now that DS 4.20 general release update is out, I expected the Create Advanced Iray Node Properties script to have been updated to create the Visible to Primary Rays parameter. Sadly that hasn't happened. So implementing the "supported ghost light solution" is still a DIY project as described above.
Not only that, but "visible to primary rays" alone is not enough to create a ghost light, you also have to fiddle with the other material parameters. And it will not behave as a ghost light as before anyway, but something similar. So, it's not back compatible. Specifically, to mimic the old ghost lights, one needs to hide the camera and shadow and reflection rays from emission, but not from the opacity map. This 4.20 can't do.
Personally I still believe the blog post is deceiving to the users. The 4.20 solution does not "fully support" ghost lights, nor it is enough to "flag" the light. Other than you have to be an iray expert to flag the light, because the daz script doesn't work. So the common user will never be able to do that.
https://blog.daz3d.com/daz-studio-4-20-volumetric-clouds-smoke-and-fire-effects/
We implemented the old ghost lights into diffeomorphic though, so all the scenes previous to 4.20 will work fine in blender.
https://bitbucket.org/Diffeomorphic/import_daz/issues/974/ghost-lights
Fully supported as in theya re using official features of Iray and so, bugs aside, should continue to work in a predictable manner. Not that I wouldn't have vastly preferred a Bollean toggle for multiplying Luminosity by Opacity.