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LED lighting with IES data

Posted: Tue Sep 25, 2012 3:33 pm
by feynman
Maybe I asked wrong. So I import a primitive sphere, scale it down and apply an IES emitter MXM > IES sphere points down (default) > I rotate the primitive sphere until the "attached" IES sphere points into the right direction > I clone the now correctly oriented primitive sphere and would like to rotate it around the worldspace axis > this does not work, because one can only rotate the sphere's in its local coordinate system. If I click "Reset" it gets "zeroed" - but the IES sphere will point down again. Question: how can I rotate a locally rotated object globally?

See also edits below first image...

Thanks!

ps: the manual advises to use small spheres for IES emitter lighting, but is that also the case for LEDs - flat directional emitters?

pps: "Reset" does not reset the selected object's position, scale and transformation values - it zeroes them; like in CAD software, it should rather be named "Zero Transforms" or something not misleading.

Image

I thought one could move the pivot of the initial LED sphere to the centre and then revolve clones around the centre. But what happens is that the IES sphere is moved when moving the pivot. Is that supposed to be so? And, even with the IES sphere moved away from the LED sphere, the light is emitted from the location of the LED sphere, not the new location of the IES sphere?! Anyone knows why the IES sphere remains "attached" to an object's pivot? Does not make much sense to me and it makes certain very slim and pointy IES spheres hard to place and direct when using the same LED, cloned, in many locations where rotation and translation is needed to place them.

Image

Re: LED lighting with IES data

Posted: Wed Sep 26, 2012 7:09 pm
by feynman
BUMPDEEBUMP... Anybody knows how to position the sphere and the IES sphere applied to it via the MXM so they remain together? Nothing at all about that in the Cnowledgebase, etc.

Re: LED lighting with IES data

Posted: Tue Oct 02, 2012 11:17 pm
by feynman
BUMP

Re: LED lighting with IES data

Posted: Wed Oct 03, 2012 12:31 pm
by Mihai
The IES file/preview it self is always attached to the objects pivot and rotation values. It does not have any separate controls for this. It would be pretty confusing otherwise I think. Think of the geometry as the lamp itself, not IES vs geometry.

Re: LED lighting with IES data

Posted: Wed Oct 03, 2012 12:49 pm
by dariolanza
Hello feynman,

About your questions:

In Studio you have an option to switch between the Local transformation to World transformation (in the main bar) so you can decide how to transform your sphere primitive.

Yes, the IES must always be applied to an small sphere no matter the shape of the light lobe or the nature of the lamp. This is because the definition if the IES data capture.
Doing that, you ensure you recreate the original conditions, and the light distribution you will get will match the original (in case of an LED, its corresponding light shape).

Cheers

Dario Lanza

Re: LED lighting with IES data

Posted: Wed Oct 03, 2012 5:24 pm
by feynman
Thanks both for your replies. Yes, I'm aware of local vs. worldspace pivot setting and I have no qualms with IES lighting results as such, it works very well. The problem is: I load a sphere from the library. I assign the IES MXM to it. I then see the IES sphere. I rotate the library sphere so the IES sphere faces the right way where my LED is directed. Then, for ease of use, I want to clone and rotate the library sphere with the IES sphere 6 times around the centre or some other location so the chandelier ends up with the 7 LEDs used. For some reason, probably me not finding how to do this in the manual, I can only get the desired result if I put the pivot of the library sphere in the rotational centre - which moves the IES sphere to that pivot point location also. I would have found it more intuitive, if the IES sphere would stay "attached" to the object it is assigned to via the MXM, not stay "attached" to the object's pivot - which may need to be moved elsewhere like in my clone and rotate case.