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Iray Lighting Process

DekeDeke Posts: 1,635
edited December 1969 in New Users

I'm reading what I can on Iray lighting and watching SickleYield's videos on the subject. What I can't seem to figure out is how to add lights as I did when rendering in 3Delight. None of them have any effect. Does Iray not see these lights? Do I need to add a different kind of light? In Render-Editor-Environment I have the mode set to Dome and Scene, but only the dome lights the scene. Do lights in Iray have to be physical objects set up as emitters?

Comments

  • DekeDeke Posts: 1,635
    edited December 1969

    Answering my own question here. Seems that for Iray to recognize lights they have to be photometric lights.

  • Man Behind the CurtainMan Behind the Curtain Posts: 61
    edited December 1969

    I've been having a problem lighting an Iray render as well. If I just add lights like I do for 3Delight, I get a completely black render. I read that you mentioned adding photometric lights for Iray to use them, but I can't find how to add a photometric light. Any idea where you find these? thanks.

  • BeeMKayBeeMKay Posts: 7,019
    edited June 2015

    Photometric lights are combined with the regular lights.
    You will have to crank up the lumiance for the light to show results.
    I made some examples here for all the standard lights a while ago:
    http://www.daz3d.com/forums/viewreply/820983/

    A good starting value is around 45.000 units in lumiance for all lights except for distant light, which has to be toned down to 10-15 units in lumiance.

    Post edited by BeeMKay on
  • Man Behind the CurtainMan Behind the Curtain Posts: 61
    edited December 1969

    Thanks, super helpful!

  • DekeDeke Posts: 1,635
    edited December 1969

    Can someone define photometric and how these "lights" differ from the regular ones?

  • SickleYieldSickleYield Posts: 7,644
    edited December 1969

    I'm using kcd/m^2 units for everything now. Lets me use much smaller numbers. :D When I started out with lumens I would have to use millions to light a scene!

  • BeeMKayBeeMKay Posts: 7,019
    edited December 1969

    dkutzera said:
    Can someone define photometric and how these "lights" differ from the regular ones?

    It's basically different maths.
    The 3Delight lights give light information in a way that 3Delight works with (for its biased engine). The photometric lights use the physics formula as a base for telling Iray the light information (for the unbiased engine).
    https://en.wikipedia.org/wiki/Photometry_(optics)

    http://knowledge.autodesk.com/support/3ds-max/learn-explore/caas/CloudHelp/cloudhelp/2015/ENU/3DSMax/files/GUID-E337DCA6-6B8D-4689-BCB8-6A6EEF06E6EE-htm.html

    Photometric lights use photometric (light energy) values that enable you to more accurately define lights as they would be in the real world. You can create lights with various distribution and color characteristics, or import specific photometric files available from lighting manufacturers.
    Note: Photometric lights always attenuate using an inverse-square falloff, and rely on your scene using realistic units.

    When you create lights from the Create panel, photometric lights appear as the default.

  • evilded777evilded777 Posts: 2,466
    edited December 1969

    Ummmm

    Rather than crank up your lights, or switch to KC/m2... why doesn't one use the Tone Mapping?

    That's what its there for, after all.

    A few simple exposure setting changes will make a world of difference.

  • SpottedKittySpottedKitty Posts: 7,232
    edited December 1969

    A very good point about Tone Mapping — the default settings are just about right for high noon on a cloudless bright sunny day. Rendering a low-light scene with those settings pretty much demands unrealistically high light settings, which might have other effects on how good the rendered scene looks. It's a juggling act, I usually have to adjust both light values and tone mapping settings to get good results.

  • Steven-VSteven-V Posts: 727
    edited December 1969

    I use a combination of changes to the tone mapping (usually F stop, but sometimes shutter speed or ISO) and changing the light. Basically I try to get it fairly close with the light and then try to adjust within about 1 stop to get the exposure "just right."

  • mjc1016mjc1016 Posts: 15,001
    edited December 1969

    Generally, unless one is shooting in a studio or has exclusive use of a location, or is a professional photographer, then one is stuck with whatever light is already existing....

    So, how do you 'fix' a scene with sub-optimal lighting?

    You adjust your camera...or in the case of a render...the tone mapping.

    Basically, set up your lighting with 'sane' values and if it isn't enough...adjust the 'camera'. Because upping the lighting does affect the 'realness' of things like shadows (minimally)...it can make them much harsher, for one.

  • BeeMKayBeeMKay Posts: 7,019
    edited June 2015

    :-) Why cranking up the light rather than fiddling with the tone mappping? Because it's a lot easier.
    Yes, adjusting the tone mapping is probably the more realistic approach, and if you have a nice, easy to use basic list of settings for tonemapping adjustements for standard situations, I'm all ears. :-)

    Post edited by BeeMKay on
  • evilded777evilded777 Posts: 2,466
    edited December 1969

    lee_lhs said:
    :-) Why cranking up the light rather than fiddling with the tone mappping? Because it's a lot easier.
    Yes, adjusting the tone mapping is probably the more realistic approach, and if you have a nice, easy to use basic list of settings for tonemapping adjustements for standard situations, I'm all ears. :-)

    I'll throw one out for you

    Indoor scene, rather well lit and with some ambient light coming from windows etc:

    ISO: 400
    Fstop: 4.8 or 6
    Shutter Speed: 1/92 or 1/60

  • BeeMKayBeeMKay Posts: 7,019
    edited December 1969

    Thank you, that is a starting point.

  • DekeDeke Posts: 1,635
    edited December 1969

    What is tone mapping? Where is is controlled. It does make perfect sense to…for instance…have some f-stop controls along with other camera controls. I see that I can adjust Fstop in the Camera Page….Editor…but it has no effect on my seeing the image in the View pane. That image is still black. There seems to be no correlation between the preview image and the Iray rendered image.

  • SickleYieldSickleYield Posts: 7,644
    edited December 1969

    dkutzera said:
    What is tone mapping? Where is is controlled. It does make perfect sense to…for instance…have some f-stop controls along with other camera controls. I see that I can adjust Fstop in the Camera Page….Editor…but it has no effect on my seeing the image in the View pane. That image is still black. There seems to be no correlation between the preview image and the Iray rendered image.

    https://www.youtube.com/watch?v=qa07FN44w7Y

  • DekeDeke Posts: 1,635
    edited December 1969

    Bless you SickleYield.

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