Making lights work in Iray renders
winddancer6440
Posts: 49
Well I love the Iray renders but am having a bear of a problem understanding the lighting system and putting in lights ane making them work the way I intend.
They either have little or no effect or i come up with a black screen. As far as what I am using, asus 99 with amd 8350 8 core 4ghz cpu, 32 gb ram, nvidia 9750 cudacore 4gb graphics card. so I have plenty of computing and graphics power.
Lights are my undoing, they either show as burning , to much light or blackend to little light. Uber lights don't convert well i have noticed. standard lights do not react as intended. so I need some instruction on how the settings work if anyone can help.
Thanks
Jim Morrison
Daz 3D is part of 
Connect
DAZ Productions, Inc.
224 S 200 W, Suite #250
Salt Lake City, UT 84101
Licensing Agreement | Terms of Service | Privacy Policy | EULA
© 2024 Daz Productions Inc. All Rights Reserved.
Comments
A simple way to tackle lighting in Iray...pay attention to your camera settings/tone mapping. The default settings are for a bright, sunny day...the default HDRi on the Iray dome. Changing away from the dome to scene lighting means you need to adjust things like exposure.
Are you using photometric lights (point, spot, distant), emissive surfaces or HDRIs to light your scene. If you are using the default photometric lights at the default tonemapping settings - you'll need to boost the lumen units by a large margin.
In DS 4.8 you actually have to set your photometric light down to 1500.00-->15.0 when using it in conjunction with HDRI environment lighting, however, in DS 4.9.054 you do have to blast the P-lights to 1500---->15000.
Takezo, I don't follow what you are saying here. Also, there should be no difference in Photometric lights or their usage between the the two versions. I'm pretty sure that there were no changes that affect lights in the beta... though I may be wrong; but I am not lighting any differently in the beta.
In 4.8, photometric lights don't necessarily need any change from default, nor do the tone mapping to get a reasonably lighted scene. Attached is G3F w/ 1 photometric spot @ default 1500, default tone mapping, default hdri
Here, let me give you a visual.
This is from DS 4.8 Using default distant light via photometrics. 1500.0/6500.0...And from DS 4.8 Using decreased distant light via photometrics. 10.0/4500.0
Next is from DS 4.9 Using default distant light via photometrics. 1500.0/6500.0... And from DS 4.9 Using default distant light via photometrics. 45000.0/4500.0
Agreed, the distant light in 4.8 needs to be scaled down by a large margin. Points and spots appear to be the reverse for me.
Yes, but to be fair to daz, most big-boy 3D apps use the same for their photometric lights in the same way as DS 4.9, so Daz is going in the right direction in aligning themselves in the same way as the pro-3d progs in order to maintain an equilibrium in work flows between themselves.
Ahh...now I see. I don't recall seeing "distant" light anywhere in the discussion up until that point (except someone asking if they were using spot/distant/point).
The original statement included all photometric lights.
A distantlight is hard to determine using luminous flux.. luminous flux is the light strenght of a light source...and a distance light is like a infinit "chain" of light sources... there is no light loss...
So in DAZ4.8 we had actually the light output of a 100w indescent bulb (1500lm infinit) directly and everywhere on our objects... that was WAY to bright..(there is also no spread angel on a distance light.... the light paths are all parallel..(no loss!)
in 4.9 it looks as they corrected this (mistake) and use something like the illuminance lux (lux on a surface) with a view angel of 360 and 1m distance as the constant light flow calculated from lm.(our input)...
A example would be input 10000lm (with 360view angel and 1m distance = 798 illuminance lux... this is about the "brightness" like in a office or supermarket...i cant say if they used exactly this formula values but that's how it should be done. for distance lights...and that looks now way better to me in daz 4.9.
For simplification here some basic start values for mixing distance lights with HDRi..
Overcast day = 1000 illuminance lux -> <> 12500lm
Full daylight = 10000 illumincance lux -> <> 125500lm
Twilight = 10 illuminance lux -> >= 125lm
Indeed, on a clear day with no humidity I use 250000lm in order to match the HRI that I'm using, but with your calc/list I can now use the proper settings, and yes, I'm glad daz is going this iRay route!Now only if they can match environmental lighting for ground cast shadows while using HDRI!
No worries, as it's such a drastic change it would be hard to believe it unless it's actually been illustrated...I mean, I was irritated when I first used it, but fully accept it as daz is growing into it's own while adhering to established industry standards! ;^)