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I have been consistently trying and failing to recreate the techniques described in the links to create an IES like textured light effect with Cycles Spotlight lamps using a Color Ramp node.

http://blenderartists.org/forum/showthread.php?264052-IES-Like-Lights-in-Cycles-Architectural-Lighting or

http://www.elysiun.com/forum/showthread.php?264052-IES-Like-Lights-in-Cycles-Architectural-Lighting/page2

According to the images you need the Dot Product between the Normal with Incoming connected to a Color Ramp node; however recreating the described node setup does not yield the same desired effect as shown bellow.

Dot Product

Using Add instead of Dot Product seems to show some effect, but it's not the expected result.

Add

Those images seem to be from older versions of Blender, using 2.65 and above I have never been able to achieve that effect. Did something change internally that broke these techniques, or is there a new workflow to achieve the effect currently?

Did I miss something obvious? Hopefully someone with better math knowledge can solve this.

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    $\begingroup$ Dot product is the way. Couldn't be just a matter of setting the handles in a different positions? Without any kind of remap, values tend to be all in one place: maybe you missed them. Here's a screenshot of my testfile: imgur.com/8M1c3PR $\endgroup$ – Carlo Feb 26 '16 at 16:03
  • $\begingroup$ The problem was not the handle position but your answer made me realize my mistake. What I did wrong was the light type, it must be an areal light, not a spot lamp. Thanks for the help $\endgroup$ – Duarte Farrajota Ramos Feb 26 '16 at 16:23
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    $\begingroup$ Note that native IES support is in the works and there is already an addon allowing it. $\endgroup$ – PGmath Feb 26 '16 at 17:15
  • $\begingroup$ I knew about the addon, but never actually gave it a try,but with the upcoming patch it will hopefully become obsolete. I've also been following the patch for a while now, looking forward to those improvements as they will come in handy here is the link for the project developer.blender.org/D1543 and thanks for the info. $\endgroup$ – Duarte Farrajota Ramos Feb 26 '16 at 17:31
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I did miss something obvious, thanks to Carlos comment I solved what was wrong with my scene.

The problem was not with the node setup itself, but with the object data. Light type must be an Area Light, not a Spot Lamp.

Using the correct area light type now yields expected results.

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