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I was trying to define the intensity distribution of a light source by an IES texture. Since I need to account for the aperture size, I model the source by a rectangular plane and apply an emission shader to it. The "strength" is then modulated by the IES texture.

I found several threads on stackexchange that at least touch the problem. The exact methods can often not be applied any more, since the UI changed with releases. Most of all, I could not find any definitive description on how to rotate a mesh light source that has an IES texture attached to it. I guess that the "vector" input of the emission shader needs to be adjusted - but this is not really explained in the documentation.

Does anyone have a working example with a recent (4.x) Blender release that shows how to rotate a mesh light together with its IES texture?

Best, Lars.

(Fixed some typos that the answers refer to)

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    $\begingroup$ Do you have an minimal example file (you can provide one here: blend-exchange.com and include the link in the question) I don't see why you can't just rotate the mesh? And the Emission Shader has no vector "inout", what are you referring to? $\endgroup$
    – taiyo
    Commented Jun 13 at 15:28
  • $\begingroup$ @taiyo That's just a typo, the "vector inout" is the "vector input" (o and p are next to each other on the keyboard, not so hard to guess 😉). But there's no example needed: the question clearly says he's using a mesh light, IES textures are for light objects, not mesh objects. $\endgroup$
    – Gordon Brinkmann
    Commented Jun 13 at 16:58
  • $\begingroup$ @GordonBrinkmann haha omg, i really was into "in out" so i didn't think of that xD And yea, the setup instructions were also crystal clear, so i was super curious how he did that "mesh IES light". $\endgroup$
    – taiyo
    Commented Jun 13 at 18:22

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IES texture works assigned to light objects, like Point type (not mesh objects) ... there I don't have an issue to just rotate the light object so texture is rotated accordingly in 4.1

If you need to rotate texture (instead object) manipulace Normal value ...

enter image description here enter image description here

For more info try check ref. Manual or here result of quick search ...

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  • $\begingroup$ Thank you all for the answers. I found out that there is a problem is related to using the GPU (here on a Macbook Pro with Apple M1), that gives me a black surface when I apply an IES to the emission shader. Switching to CPU renders the emission. Interestingly, this gives me a plausible result first - but when I rotate the surface around its axis by 180 degrees, I get only artefacts. $\endgroup$
    – larsg
    Commented Jun 13 at 17:50
  • $\begingroup$ All this is hard to reproduce - switching back to GPU gives me a result, too, now. I guess I need to setup a minimalistic scene to further test. Rotation, GPU / CPU $\endgroup$
    – larsg
    Commented Jun 13 at 18:24
  • $\begingroup$ I would suggest to you -share your simplified blend file (as described by taiyo) so we can check your setup and test it on other machines, but yes from your screens it looks like an Apples M1 issue (I'm working on Apples Intel), but without your file it will be always a guessing. $\endgroup$
    – vklidu
    Commented Jun 13 at 19:24

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