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Unable to change IES intensity scale after setting it once


i think i encountered a bug in the editor. I'm using Spotlights as static IES light sources. So far, so good. I mimicked the example from the realistic rendering scene and used the complex.ies file as profile. Afterwards i ticked "Use IES Intensity" and set the scale to "0.2". After the bake-process, i wanted to alter the scale a bit, but noticed, that i couldn't. The "Use IES Intensity"-checkbox is grey (disabled, checked for true), the scale remains at 0.2, the usual intensity value is also grey and disabled. I can't even change the IES-profile-texture to something else. Seems like the whole settings froze.

Is that expected/known behavior or a bug? Am i missing a point?

Best regards


Some additional information to the bug:

Editor-Version 4.2.1-2101290 (installed via Launcher, not self-compiled)

I'll look into how exactly to reproduce it later today.

Product Version: Not Selected
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asked Jul 01 '14 at 03:41 PM in Bug Reports

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avatar image Lovecraft_K ♦♦ STAFF Jul 01 '14 at 09:31 PM

Hi LeFxFlo -

Thank you for your report. I will begin investigation into this issue as soon as possible. If I am unable to reproduce the problem, or I need more information, I or another staff member will follow up with some additional questions for you. Otherwise, I will post an ‘Answer’ once I have logged the issue in our bug database or we have a solution for it.

In the meantime, please be sure to review our suggestions for how to report a bug, and feel free to edit your post if you have additional information to provide: https://answers.unrealengine.com/questions/12363/how-do-i-report-a-bug.html

Thank you.

Eric Ketchum

avatar image LeFxFlo Jul 02 '14 at 02:27 PM

I noticed something, after continuing to work in the scene:

I can "re-enable" the instensity scale and the ies-texture, when i set the light to stationary or movable. Then i can change the values to something, that feels appropriate and switch back to static for baking (which locks the values once again). This works, is just a bit complicated and emphasizes my thought, that this must be a bug.

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Hi LeFxFlo -

I was able to reproduce this only by switching the light to Static which will not allow alteration to a Light Profile. Check to see if that is the case with you and then Change the Light Type from Static to Stationary or Movable and you should have control of your Light Profiles again.

Thank You

Eric Ketchum

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answered Jul 02 '14 at 02:37 PM

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Lovecraft_K ♦♦ STAFF
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avatar image LeFxFlo Jul 03 '14 at 08:49 AM

Same for me.... When the light is static, the options are frozen. When light is movable or stationary, things are working. Is that considered to be standard behavior?

avatar image Lovecraft_K ♦♦ STAFF Jul 03 '14 at 01:53 PM

Yes, this is working as intended. The IES Light Profiler works in a similar way as Lighting Functions, but uses pure math instead of an actual texture sample.

Thank You

Eric Ketchum

avatar image LeFxFlo Jul 03 '14 at 03:20 PM

Hi Eric, thanks for clearing this up.

But why does it freeze the settings when it is set to static? I mean...it's a bit inconclusive to me, that i have to switch my lights to stationary/mobile everytime i want to change the ies profile settings prior to building the scene.

I - personally - find this to be not very intuitive...but that could be just me ;)

avatar image whooosh Jul 25 '16 at 11:55 PM

Something similar is happening in 4.12.5.


  1. Create a light

  2. Make it Stationary

  3. Input an IES texture

  4. Use IES Intensity = TRUE

  5. Change to STATIC

  6. Regular light intensity is greyed out.

  7. No way to edit ANY light intensity at this point.


  1. Switch back to Stationary

  2. Use IES Intensity = False

  3. Switch to Static

  4. Regular light Intensity is now editable.

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