Iray Spot Lights Bug or not?

Szark

I can't show you the scene I am working on as it is work.

 

However I have 25 Spot Light set up, 12 at ground level, well just above really. The rest are up on an upper level.

 

All the spots have the same settings, same emitter shape and size etc etc. 

 

When all lights are on the lower spots start to get interference from the upper lights to the point where a few of the lower ones have a lower intensity.

All the Upper lights work perfectly when all lights are on.

When I remove, turn off or lower (to the same level or below the lower set of lights) the upper lights, the lower set works as it should.

I have checked everything over the last day and a half and finally found it to be any spot a lot higher than some causes it for me. This is in Interactive and Final Render mode. 

Iray render engine Dome and Scene, Scene only etc. I have tried just about everything I can think of to eliminate me or the meshes and mats.

Tobor

I don't know what "Final Render" mode is, but there's a limit to the number of light sources in Interactive mode. According to the docs there's a limit of 16 light units, and you''ve exceeded that.

http://www.migenius.com/doc/realityserver/latest/resources/general/iray/manual/index.html#/concept/limitations_interactive.html

There doesn't seem to be a similar light unit limitation with Photoreal, but there are other limitations, which could be at issue depending on your scene:

http://www.migenius.com/doc/realityserver/latest/resources/general/iray/manual/index.html#/concept/limitations_photoreal.html

Apart from that, the problem could be a bug in Iray, or a scene collection issue in D|S. If you continue to have the problem you might want to send a bug report to Daz.

Szark

Thanks Tobor

Final Render Mode...ie doing a proper Photoreal render. Interesting that the limit in Interactive more is 16 as I have 25 and only 6 have issues and if that was the case I would see all them working in a final render. 

Tobor

Though a shot in the dark, you might see if the scene works by inserting just one spot and instance it as many times as you need. If you try that please let us know whether or not it works. Playing with the Speed/Memory geometry instancing setting in the Iray render panel might have an affect here, too.

If you're brave, you might try creating a row of spotlights on a single emissive plane using an IES profile. This should work in theory. The idea is that you can take a profile for a single spot, and duplicate its nodes for as many lights as you need. When applied to a plane of the proper size, you should be able to get (for example) a series of 12 spots. 

IES profiles are text files, and their construction is documented in a number of places. Here's one that came up first on a Web search:

https://docs.unrealengine.com/latest/INT/Engine/Rendering/LightingAndShadows/IESLightProfiles/index.html

The discussion is for the Unreal Engine, but the idea works the same in Iray. I recall seeing an IES profile generator somewhere, but I can't find it now.

 

 

Tobor

Hmmm.... On second thought, a single profile of multiple lights doesn't look possible. Though the profile specs allow for declaring the number of lights, everything I'm seeing is limited to just one light. I was hoping it would be possible to define an offset so a single profile would replicate multiple lights sources, which is the case of an lamp made with multiple LEDs. Oh, well.

Since geometry meshes naturally support instancing, this might be a way to fool Iray into thinking there's just a single light source. How this works would likely depend on the Speed/Memory setting. Here's the technical details on what goes on when you change this setting:

http://www.migenius.com/doc/realityserver/latest/resources/general/iray/manual/index.html#/concept/instancing.html

"Off" is the same as D|S Speed setting; "On" is Memory. Be aware the Memory setting can greatly increase rendering time. In theory, what should work here is that all your instanced meshes will not be duplicated in the scene database, hopefully reducing the light sources from many to 1. That's the theory anyway!

 

Szark

Love the idea of Instancing mesh lights...I might just give that a go. 

 

This is a bug IMHO though I can't tell if it is me, my PC or DS. I can use point lights above spot and it works, I can also use spots above points and it works. It is something about spots that causes the problem. 

 

I have worked around the issue for now but I can't believe I am the only one that has found this bug.

Tobor

You could make up a simple scene with just a shaded plane in the back and 25 spots aimed at it, and others could test it to see if it can be replicated. If you report it as a bug Daz may ask for that anyway. 

There's a definite limit to the number of lights in Interactive mode, though what happens when you reach this limit isn't disclosed in the documentation. So if you have that many lights in your scene, there's no point in test rendering in Interactive, as you're then in who-knows-what land. 

Do keep in mind the documentation I pointed to is a little old, and I'm not aware of anything publicly available that's newer. So some of the things noted as limitations may no longer be, and vice versa. Example: There's a limitation listed for Photoreal dealing with volume scattering coefficient. The version of Iray in 4.9 and later no longer treats that as a scalar, but I'm not sure. This might have been one of the things they changed that also affected other aspects of materials that used volumes, such as SSS skin shaders.  In any case, it often pays to check these pages to make sure you're not trying to get Iray to do something it wasn't intended to do.

Szark

I am used to Open GL limitations and Priority settings so that isn't the issue but it shouldn't ender out with that limitation. I replaced every spot with Points and every light worked perfectly so after spending a whole day trying to figure out the issue I came to the conclusion that this is a bug. 

 

It is also interesting to note that turning off different upper spots, the lower ones that were affected would change depending on which spot I turned off. 

 

Documentation maybe old but I do learn from it so thanks again Tobor for the help.