Iray preview (mostly) ignoring emissives/ghost lights?

Petrichorian

Hi, all! I'm having an issue when using emissive surfaces in my scenes that I'm hoping someone can help me fix. I often use ghost lights (emissive primitives, usually, but sometimes commercially-sold packages) to fill in the light in specific areas of my scenes. Lately, though, the Iray preview window basically ignores that they exist when showing me my scene with "Scene Only" Environment lighting selected in the render menu. When I do my actual render they work just fine, but it's impossible to set up my scenes because the Iray preview has become useless in this respect. Point lights still work fine in the preview, but not ghost lights. It remains a problem even when I bring up old scenes where the ghost lights worked fine before.

I had to take a break from Daz for the last chunk of 2021, so it's totally possible I'm just forgetting to check something. Did I accidentally turn something off in my settings? Is this a known issue in the newest version of Daz that I missed reading about? I searched the forums, but wasn't able to find anything mentioning it in the first 10+ pages of results.

See the attached image of a plain sphere lit by a ghost light and a point light for clarification on the issue (I left the ghost light mostly visible for reference). The frame on the left of the image shows the final Iray render, with the corresponding Iray preview in the middle. I'm using the latest public release of Daz. 

M-C

Are you using the latest beta verion of Daz Studio by chance?
The latest beta comes with a new version of iray. In this new installment of the render engine Nvidia grants us with the new "feature" of a more realitic lighting approach which leads to ghost lights beeing useless. They simply do not work anymore which is a pita for most users.
But if that´s the culprit it shouldn´t work in your final render as well.

Another - more likely - possibility I can think of is the interactice render mode. Take a look at your draw style settings. If it´s set to interactive, it ignores emissive lights in general as far as I know.

 

Petrichorian

M-C said:

Take a look at your draw style settings. If it´s set to interactive, it ignores emissive lights in general as far as I know. 

That was exactly the issue, thanks! I'm pretty sure I had always kept it set to interactive, but then, I don't remember there being four settings on that Draw Style drop-down, and now there are (Photoreal, Interactive (Biased), Blend Photoreal to Render Settings, and Blend Interactive (Biased) to Render Settings). Neither of the ones that include "Interactive (Biased)" seem to include the ghost lights, while both of the others do.

Either my memory is worse than I thought (and I already thought it was pretty bad), or Daz 4.15/4.16 added new Draw Style options that changed the way plain ol' Interactive worked. My memory seems the likely culprit, though!

In any case, thanks for the help!