VRayIES and area shadow

[jonahhawk]

I've searched but I can't find the thread that talks about how to achieve this.

are area shadows possible with VRayIES? as they are via VRay Shadow in regular IES?

[voxel3d]

It is possible, you have to make sure the IES file you use has information about the dimensions of whatever lamp it emulates, and tick "use light shape" or something similar in the VRayIES properties. You can also edit the IES files directly in a text editor to give them dimensions... You would have to search for the IES file format specs to know what numbers to change...

Cheers,

Jorge

[jonahhawk]

Ah that makes sense. It would be nice to have some control of this in the light regardless of the IES file. I'm sure there is some reason why not...

[simmsimaging]

Does anyone have a couple of decent spotlight type IES files that have the shape information? I'm trying to work out a way to use Vray IES to replace Max spotlights but all the IES files I have do not seem to create area shadows and I don't know how you can tell short of d-loading a few hundred and just trying them.

Any shortcuts would be very much appreciated

b

[voxel3d]

It's easy to do this. As far as I know from reading the IES format specs, you don't really store the shape of the light in the file, it only has the ability to store general dimensions (width, length, height).

Here's the text from a standard Erco IES file (up to the point that's important for this example):

IESNA:LM-63-2002
[TEST] U100000_0
[TESTLAB] ERCO Leuchten GmbH
[ISSUEDATE] 20-11-2007
[MANUFAC] ERCO Leuchten GmbH
[LUMCAT] 22405023
[LUMINAIRE] LC Downlight
[LAMPCAT] MRC16 50W 10°
TILT=NONE
1 900 1 19 1 1 2 -0.051 -0.051 0

The important values are the last 4 (2 -0.051 -0.051 0)

The first of these specifies units (1 is feet, 2 is meters)
The remaining three values specify the dimensions of the light in said units as width, length and height, respectively.
If you change these values you give the light proper dimensions and VRay will render correct area shadows. I usually change the negative values to positive and let it be, but some of these might be pretty small, then I just make the light bigger till I get the effect I need.

If you want more info on the IES format, check out the following page:

http://www.kxcad.net/autodesk/3ds_ma...le_format.html

Cheers!

Jorge

[simmsimaging]

Thanks for the help!
I have tried this now on several IES files and while I can see the change in the light cone etc, there seems to be no difference in the shadows. They all looks super sharp. I tried several Erco lights and one that was sent to me privately the other day, but no joy.

Is there another parameter that I might need to change?

Also - you mentioned making the light bigger to get what you want - did you mean scaling it? That seems to make the VrayIES lights stop working, at least for me.

Thanks again,
b

[simmsimaging]

Okay - I'm (still) an idiot. I had turned off 'use light shape' by accident. It works fine. Thanks very much!!!!

b

[voxel3d]

Hehe NP!

What I meant by "Making it larger" was to make the numbers in the IES file, that define the dimensions of the light, larger. Ie, if it's "0.05" make it "0.2" or so...

Cheers,

Jorge

[simmsimaging]

I think it actually works if you just scale the light in Max too, you just have to be carefully to only scale X &Y. If you scale in Z the light does not work at all.

This is proving to be a great way to making nice area spotlights though. Have a look at the two attachments. One is a straight Vray plane the other is a VrayIES with a basic Erco profile, I just set it to 50cmX50cm. VrayLight is the same size

Much nicer falloff to the light and highlight as well as the spotlight effect. It renders a bit slower, but it's worth it IMO. Both are very quick lo-res tests so both are a bit too grainy still.

Great tip - thanks again!
b

[peterguthrie]

thats a great tip voxel3d, thanks!

(replying here mainly so I can find this thread again quickly )

[Neilg]

I just tried that, and i've set the ies light anything from .02 to 50.0 (in metres) and theres absolutley no difference in my render.

The higher the number, the slower it renders though. It's doing something, i'm just not sure what.
Use light shape is checked on too, tried it on and off.

[simmsimaging]

Give this one a try. It's one I edited for soft shadows and it works fine for me. The only problem I have with them now is noise. Vlado had mentioned it was something that could be optimized more like Vray lights - hoping that will be coming along soon because the light quality from these can be really nice.


b

http://www.simmsimaging.com/upload/f...0W_bsi.ies.zip

[Neilg]

That one works, but mine doesnt whatsoever :s

edit - nm, fixed it.

Thought it was supposed to have a - in front of the numbers as all our ies files did, but it seems not.

[simmsimaging]

Not sure - there will be some parameter in there doing it. Maybe it's set to inches/feet and not metric, or something like that?

[Neilg]

Sorted it - I was inputting minus values for the scale not realising it made a difference.

Thanks for the file