So was trying out the IES lights and it was not ideal!
I had one for a spotlight so expected the prefab to use a spotlight (or these more for point lights?), but it uses a point light in its prefab (which btw is bit hidden as a child of the ies file).
Edit: I see now you can set the point/spot on the IES file to avoid the error below but it could be fixed.
If I change the instanced light to be a spotlight it spams the console with errors:
Unity cannot fetch the 2D Light cookie texture: UnityWhite (UnityEngine.Texture2D) because it is not on the cookie atlas. To resolve this, open your HDRP Asset and increase the resolution of the cookie atlas.
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)
Also the intensity value was way up high, so not sure if problem reading ies file or cookie means it should be higher or…?
The highest candela value in the file is used 1967.90 but this is a massive lumens value when the light is 1386 lumens (-1 for lumens/lamp in file) - so don’t know how that is calculated
Also if you up the cookie size for an IES file it ends up breaking up or disappearing - probably because it does not fit in the cookie atlas but no good message to say what happened.
There should be auto-resizable atlas options for HDRP
Hey, @andyz , which version of engine & HDRP are you using ?
AFAIK, this has already been reported and fixed for a while.
I just tried on a simple project (with latest alpha and HDRP) and this does not repro (meaning, switching from spot to point, automatically changes the IES file from Cube to 2D)
So more detail - new release 2020.2 (so HDRP 10.2.2?)
So yes changing the spot to point on the IES works, I changed it on the instanced prefab (in scene - as did not know what I was doing - doc short on info!). This causes the error, albeit it is wrong thing to do.
Techy brightness: The light seems to take candela from the brightest level in the IES which may seem correct, except the IES files I have looked at seem to more likely have lumen values since a 390 lumen light for instance has near 390 maximum ‘candela’ value in IES file… meaning the lights are far too bright if set to 390 candela not lumen (do candela & lumen really convert as simply as presented in Unity?)
About the documentation, I’m not sure I understand, can you point where the documentation in short on info ? what information you think is missing in there ?
As for the unit question, candela unit is used to talk about an intensity per unit solid angle in a direction (roughly how bright it is).
Lumen are used to talk about the amount of visible light emitted in all directions for a source.
So Lumens can be calculated by multiplying the intensity (in candela) by the angular span over which the light is emitted.
For example, if you have a one candela light point light that can emit in all directions (full sphere of 4π steradian), if you want the luminous flux (lumens), it can be converted by multiplying 1 * 4π which is roughly 12.57 lumens.
There is no reference to the IES options is all. Also clicking the ? on the inspector for IES is a no go.
Anyway drag an IES light into scene - switch from point to spot on the scene instance - bug.
Sure but it is not working in the context of IES files that I have tried. So I have IES files for say 390 lumen bulbs (lumen is the key in UK). I import and place in scene. It sets the intensity to say 380 candela or over 4800 lumen!!
So something big is going wrong and I can only think of 2 things looking at the IES file:
The IES has lumen scale values not candela in it maybe? (the candela section have values under 400).
OR
Unity should not set its lights to the max candela value in the IES (as it seems to do), rather do something else
Fix is just for me to manually choose lumen of light - ies now attached
Thanks, for the documentation problem, I noticed there’s a lot of those link missing actually.
For the prefab it’s written in the doc here that the type is used to created the prefab.
For the Candela/Lumen problem, I’ve taken a deeper look, and it actually depends on the format of your IES file, some specify a value in lumen, some specify a value in candela and the importer work from there to make the conversion.
In IES format, there’s a value that indicate the the initial rated lumen or -1 if absolute photometry is used and the intensity values should not depend on lamp ratings (use candela instead).
In your case, your file clearly specify that it’s using absolute photometry and you can also find the -1 that confirms that.
So, unless I’m mistaken (not an IES expert), I would say this is expected to start with 387.15 candela for your file and then having a 4k+ lumen value for point light.
Yeah I agree with that IES explanation, and yet as you see it is a lowly 4.5w downlight (and external to IES file is a 420 spec. lumen one) so no way it can be a powerful 387 candela.
But anyway if you have had no problems with IES files lets put this down to manufacturers not sticking to the format properly!
