DS 4.20 Reinforced an Imporant Lesson for Me: Never Use Lighting Presets
Nyghtfall3D
Posts: 782
I've been creating 3D art since 2009. One of the first lessons I learned is that good lighting is the most important element of any image because it sets the mood and makes up 80% of your stories, which only you can tell. As such, never use lighting presets. I've gotten a bit lazy during the last couple years and often leave presets alone to take advantage of their ready-to-render marketing.
Last night, I finally bit the bullet, upgraded to 4.20, and discovered at least one of the environments in my content library - Z Shower and Lavatory - uses ghost lights. I learned this when the Iray Draw Mode rendered the environment pitch black for the first time ever, prompting me to explore the Scene tab and find that the Toilet and Shower LED's are part of two large planes spanning both parts of the envrionment across the Ceiling.
I cocked an eyebrow, thought, "Huh. Wow. Okay then," and briefly shook my head.
Looks like I get to resume my old practice of removing presets when starting new projects.
EDIT: Corrected version number in title and post.
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Comments
Somewhere there is big thread on the forums about ghostlights & how to get them working again.
Basically nVidia change the way the Cutout Opticity works, what you need to do is count the number od zero's in the Cutout Opcity and add that number of zero's to the end of the Luminace.
As an example if the Lumins is set to 10,000 and the Cutout Opcity is set to 0.0000000001 then you would add 9 zero's to th end of the Lumins value making it 10,0000000000000. The way ghostlights originally worked was by exploting a bug in the iRay shader system which nVidia has fixed.
The current DS version is 4.20, not 4.2.
I'm familiar with the thread but have never used ghost lights - not delibarately anyway. I never bought KindredArts' kits, and was critical of them of them when they came out. Light sources in the real world can't be made invisible, so the very concept behind ghost lights never made sense to me, either. I was just surprised to learn that something I paid money for does use them. Now I'm wondering how many more enivronments I've bought also use them.
Incidentally, my apprehension behind upgrading to 4.20 centered around other issues users have reported problems with, like adversely effected render times on RTX 3090 cards.
4.20
Right. Sorry. Thanks.
Your mistake was upgrading, not using a light preset. Any light presets you created in previous versions can also be effected.
Instead you could have downloaded the beta and kept your current version. Or backed up your old version. That is the reality since Daz refuses to offer its customers the option to download a previous version.
As for ghost lights, the new Iray changes all mesh lighting, ghost lights are only one part of that. Besides that, I'm not sure I understand the problem with using such a light anyway. You can make light pass through solid brick walls in Daz Studio, how is that physical? You can also make any object invisible...again, how is that logical? It is a 3d program, there obviously will be methods of cheating reality. That is part of the fun of using 3d. If Hollywood can use a green screen with fake effects that do not react realistically (since it is a green screen) then by god I should be able to create a light from an invisible source in my 3d software program. Which you can do anyway with regular point light which is perfectly invisible to the camera.
Are only ghost light products impacted, and how do i identify a ghost light? (Sorry, beginner question)
For my needs, upgrading was a question of when, not if.
I'm not in the habit of using beta versions of software. I back up my PC every week but there's no point in rolling back to 4.15 if the changes in 4.20 are here to stay. Otherwise, 4.15 is the last version I would ever use, and that's not a practical choice for me.
Can you point me to the patch notes that list other changes to mesh lights? I'd like to know how I should adapt my workflow.
Fair points.
A couple of my sets used the ghost-light trick (solid black opacity map) to avoid the light texture itself getting washed out (so you'd see the flames on one mesh but still get lots of light from a connected other mesh).
I'm waiting on a new system to upgrade to 4.20 before I can 'fix' what was broken :(
Any emissive surface that is not wholly opaque will be affected - ghost lights, where the whole surface is very nearly fully transparent, show the most dramatic effect but most flame props (fires, torches, etc.) will use one or more planes with a flame image applied and those will lose the light contribution from the transparent areas. Things like glowing holograms will also be dimmer than before.
Charles said over in the other thread that this method will lead to grainy renders. I tried it and it's true. Not recommended!
Thankyou very much, @Richard Haseltine!
If you are getting grainy renders then you don't have anough light in your scene
I did a test comparing the same scene using ghost lights in a DS version from before the fix and a version from after the fix, adjusting the numbers accordingly. I did not see any difference at all.
But when making emissive lights invisible using Cutout Opacity you don't get specular highlights and that makes a difference.