Distant Lights Don't Work in Iray in DS 4.9?
luci45
Posts: 2,780
I just bought Warhol Inspired Spot Lighting for Daz Studio Iray Vol 2. The lighting effects are all use a spot light and a distant light. The spot light works but the distant light does nothing! I haven't been using distant lights with Iray but I know they worked in DS 4.8. Anyway I tried another distant light, cranking the luminous flux up to 10000000 and intensity to 100% and still nothing.
I'm using DS 4.9.1.30.
Post edited by luci45 on
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Under render settings-->Environment, set it to "Scene Only" otherwise default environment will overpower lights.
I found that I needed to set Luminous flux on distant light to range of 20K to 50K depending on set used.
I don't have 4.9 (still using 4.8), but the proper setting for a distant light for Iray is about 10. Why this is so:
The light from a distant light is measured as incident on the scene, not from the light source. This is because distant lights are considered infinitely far away, with parallel rays. It makes no sense to measure their light from the source, because there's no falloff or beam spread.
A value of 10 means 10 candles per centimeter square, which corresponds to about the same light falling on the surface of the earth at noon day sun.
If the spot light is working, the distant light should, too, and it will demonstrate that you have the proper environment choice selected (Dome and Scene, Scene Only, etc.).
Have you verified that the distant light has not been turned off? That can be done in either of two places: Scene list (look for the open eye), or the Illumination toggle in the properties panel for the light.
Finally, note that spotlights can be placed inside things like skydomes, but distant lights are always outside these, no matter where you see the set of little three arrows that represent the light. If you have a 3Delight-era skydome in your scene, the distant light will not penetrate it.
I don't have 4.8 up anymore so I can't check flux in that version. In 4.9 the luminous flux is in Lumens. Additionally, I think that Iray lumens are based on meters instead of cm because you have to crank them up so high
Thanks. Strange I restarted DS and now the distant light works. (No, it wan't turned off before) The default intensity on all of these lights is 15% with 15 lumens. This does nothing. At 60% with 15,000 lumens the renders look like the promos for the lights. Strange.
It is OK to have dome on if the environmental intensity isn't real high but Warhol Inspired Spot Lighting for Daz Studio Iray Vol 2 seems to be scene only.
Tobor, I don't know where the 10 fits in and I don't use a skydome with iray. The dome in "Environmental Mode" doesn't block the distant light. I think the numbers are different from DS 4.8 to 4.9. I remember the intensity being really low before.
I put in a support ticket anyway and thanks again for your help.
Correct on the lumens; I had meant to write 10 lumens/cm^2.
The default scene unit for all lighting in D|S is the centimeter, so if they changed this to meter, it would have been an odd things to do, but it would account for the variation in the rendered scene, but doesn't explain why the light wasn't working (see the follow up, it's now working for the OP).
In 4.8, I don't have to crank up the value any higher than 10 to get a very bright light at default Tone Mapping settings. I'd be curious if someone with 4.9 could test it. Just add a single character, one distant light that points down at maybe 30 degrees toward the character, and select Scene Only. Change the Luminous flux of the light to 10, and render at standard tone mapping settings. What happens?
@luci45, there's no point in using the percentage setting with photometric lighting, and using the Intensity dial is the wrong way to set light levels in Iray. It probably won't hurt to leave it if it's working, but in the future for your own settings, keep the intensity of all photometric lighting at 100% and change the luminosity value instead. The photometric settings are provided for Iray lighting for a reason, as they support the proper physics of the lights.
Note I said a 3Delight-era skydome -- they are not the same as the Iray environment dome. Skydomes are physical geometries that will block lighting in Iray. You didn't post an example of your scene, so it was impossible to know what's in it. Skydomes are a common cause of lighting issues in Iray.
I already explained where the 10 comes from and how it works -- that value corresponds to the light incident on the ground at noon from the sun. Use it as a starting point. As your distant light is no doubt passing through a geometry that acts as a scrim or gobo in order to produce the pattern, That would require the light output to be increased, just as it would in the real-world. In any case, glad it's working for you now.
Regarding distant light setting in DS 4.9. Here are 3 of Genesis 3 Female, 1 distant light down 30 degrees, left 30 degrees
The first is Luminous Flux at 10, second is at 1500 (default value) and last at 15000.
Curiousity got me to re-install DS 4.8 on system.
I think I mostly stopped using distant lights after Iray was integrated into DS.
Didn't use them much to begin with. I'm surprised this hasn't come up more often.
But the pictures speak for themselves, both were made with luminous flux set to 10 in respective versions.
Maybe someone would like to file bug report? (1)I am terrible at such (2) really don't care that much.
Thanks for investigating this. I don't recall Daz saying they altered the distant light metric, and don't know why they would, as it's a major breaker of scenes. Maybe it is a bug.
In 4.9, could you do one more test? Render at 100000. That would be 10 times 10000, where the 10000 is difference between calculating between cm^2 and m^2.
A pair at 100,000 luminous flux. I changed backdrop on 4.8 as it blows out
Edited to add
4.9 at 100K compared to 4.8 at 10
Looks like it's been changed to m^2 to me...the 4.9 100K and 4.8 10 look virtually identical from where I'm sitting.
@Medzin, thanks, again!
Yes, it looks like that to me, too. Why they did it, is another thing. It could be a bug -- there's a units setting in the MDL def that defines the scene scale. It defaults to m^2 in Iray; and has to be specifically changed to represent cm (or inches or feet or). So now, we have distant lights that work in meters, but spotlights and point lights that work in centimeters. There's also emissives, where you can choose the scene scale, and you can pick the one you want.
If it's not a bug, the change is unfortunate. I'm never a fan of breaking changes, unless absolutely required.
If points and spots are still cm^2, it sounds like a bug to me...and should have a support ticket opened.
I don't know that they are, but I assume since that would be a much bigger change for people. I would guess that if the dimensions of the area emitters are still stated in centimeters, the total luminous flux value should be as well.
I'm not the best to open a support ticket because I don't have 4.9. I can't install it until after October, when a big project is completed. Any change in behavior would require my redoing months worth of work, so that the renders match.
I'm not good for it, either, because I'm stuck in 32-bit land (although the most recent WINE and 4.9 64 bit is now hanging at starting the CMS instead instantly crashing...).