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Need some Iray Lighting Advice

tl155180tl155180 Posts: 994
in The Commons

Hi All,

So, I'm in need of a bit of Iray lighting advice from all you experts out there. I'm lighting a room within a sealed geometric box-shaped set (so no HDR and no windows - Scene Only lighting) and I'm torn between:

(1) The realism of using emissive shaders on all the lighting props, which lights the whole room appropriately but casts lots of conflicting shadows that look poor on the figures, or...

(2) Using portrait lighting on the figures, which picks them out very nicely, but then scratching my head as to how to light the rest of the room without ruining the portrait lighting.

 

Does anyone have any good tips on how to light a whole room, but still be able to use softer portrait lighting on the figures within please? (Remember - no HDRs).

Comments

  • ToborTobor Posts: 2,300

    If this were a real shoot, and beauty is a key, I would light this using studio lighting, and then add the practical lights for effect. They can have low emission, something that looks like they're turned on, but don't contribute a lot to the actual lighting. You want realism, but also want good looks. This can be challenging.

    These days I'm preferring parametric spots with the emitters changed to large rectangles, as opposed to planar mesh lights. The values for the width/height appear to be in centimeters. For a broad softbox to act as fill, something a couple feet square might work. Adjust the size and other parameters to get the shadows you want. You can elect to hide the emitter during rendering. Remember these lights respect inverse square law, so the further from the subject, the less light.

  • tl155180tl155180 Posts: 994
    Tobor said:

    If this were a real shoot, and beauty is a key, I would light this using studio lighting, and then add the practical lights for effect. They can have low emission, something that looks like they're turned on, but don't contribute a lot to the actual lighting. You want realism, but also want good looks. This can be challenging.

    These days I'm preferring parametric spots with the emitters changed to large rectangles, as opposed to planar mesh lights. The values for the width/height appear to be in centimeters. For a broad softbox to act as fill, something a couple feet square might work. Adjust the size and other parameters to get the shadows you want. You can elect to hide the emitter during rendering. Remember these lights respect inverse square law, so the further from the subject, the less light.

    Thanks for the advice Tobor - this is actually exactly along the lines I've been thinking, setting the emissives up to only look like they're contributing fully to the light in the room while really getting most of the light from softbox portrait spotlights. To me, this kind of lighting looks much better than trying to do it the realistic way with lights all over the room (which I don't think Iray handles very well, in my opinion).

    The problem I'm having with this though is that the room is pretty darn huge and areas that aren't being directly lit by the portrait lights are looking way too dark and unlit. Not sure how to get around that...

    I've seen images done by artists using Poser / Octane where they 'appear' to be using only practical emissive light props for their lighting and I can't work out how the hell they've done it because it seems to light the whole room very evenly (even under tables etc) and blend the shadows very well, whereas I'm not convinced that Iray is capable of that. Someone told me once that Octane lighting has a lot more fill to it than Iray lighting, so maybe thats why.

  • mjc1016mjc1016 Posts: 15,001

    If this were a 'pro' photoshoot, in all likelyhood they would be setting up a ton of lights to light the figurres and 'faking' the rest of the room with fill lighting.  It's hard to say what's 'real', these days.  Just remember, Iray does have very realistic fall-off for it's lights  AND size does matter.

    Also switching to a different, not Watts. scale for light output should help.  And if you do want to do the 'lights all over the room', attaching IES profiles to those lights will help make them behave.

  • ToborTobor Posts: 2,300

    Since you're lighting this theatrically (as opposed to using just existing light), for your back walls or any scenery, you could light those with most any technique that fits your goal.They could be individual spots, or a long emissive plane if you're going after a flatter look. If you use spots you can make them big to lessen shadows, visualize through them in the viewport to make accurate adjustments, and hide their emitters during the render.

    I've lit some Iray scenes only with practicals -- The Conference Room here on Daz lends itself to it. Turn the overheads into working fluorescents, and provide some light through the windows (I used the default Ruins HDR for that). Fully lit, had the appearance of ambient occlusion under desks, chairs, and ceiling/wall. Looked very real. Also took four hours just to get to ~5% convergence. Ouch.

  • mjc1016mjc1016 Posts: 15,001
    edited July 2015
    Tobor said:

    I've lit some Iray scenes only with practicals -- The Conference Room here on Daz lends itself to it. Turn the overheads into working fluorescents, and provide some light through the windows (I used the default Ruins HDR for that). Fully lit, had the appearance of ambient occlusion under desks, chairs, and ceiling/wall. Looked very real. Also took four hours just to get to ~5% convergence. Ouch.

    For those converted flourescents...if they were double sided, that could be one reason for the long render time.  Making them single sided should speed things up.

    Post edited by mjc1016 on
  • tl155180tl155180 Posts: 994

    Thanks guys (I assume you're both guys?) laugh. I suppose I could just fill the whole room with spotlights and the like, but I was hoping to avoid that. I wish there was a way to just raise the ambient light levels in a room like we have with 3Delight and uber-environment light, but I guess the Iray developers would say that isn't very realistic. I know theres tone mapping, but that will tend to blow out your scene lights if you raise it too high.

    When I first started playing with Iray I was really impressed with how natural the light looked and the realistic fall-off etc, but the more I play with it the more I agree with those who say that its only a minor improvement over 3Delight. I really think that nvidia haven't gotten the ambient occlusion right and the shadows just don't look realistic to me unless you go full-on studio portrait lighting. Call me overly critical, but I was hoping for better. I suppose it is free though, so I shouldn't really complain.

    I wonder if Octane would be better though...

  • ToborTobor Posts: 2,300
    mjc1016 said:

    For those converted flourescents...if they were double sided, that could be one reason for the long render time.  Making them single sided should speed things up.

    Single sided for sure!

    Feel sorry for me, because I don't yet have a GPU that supports Iray. I do have a dual-CPU Xeon, but that's only as fast as a decent i7. So my render times will seem pathetically slow becase, well, they are!

    On 3DL versus Iray: the process is different, to be sure. But because I come from a photography background, even going back to chemical darkroom stuff in the late 60s, I'm more comfortable with non-biased renders, setting up lights, and so on. I have not used Octane other than a quick trial, but if it works for you, then the expense might be worth it. You might also try Reality. I have it for both Poser and D|S. It does a nice job, too, but you still have to light things carefully.

    With Iray, you can still construct an environment and light globally. Assuming the walls of this room are white, use it as a giant uber environment. Render times are going to increase, but it might have the look you're going after. IThink about how it would look if it were a real room. A 3- or 4-point portrait light setup in the middle of a big room is going to leave shadows in the deep background. Your Iray scene will be no different. 

    That said, have you tried making those back walls slightly emissive? 

  • tl155180tl155180 Posts: 994
    edited July 2015
    Tobor said:
    mjc1016 said:

    For those converted flourescents...if they were double sided, that could be one reason for the long render time.  Making them single sided should speed things up.

    Single sided for sure!

    Feel sorry for me, because I don't yet have a GPU that supports Iray. I do have a dual-CPU Xeon, but that's only as fast as a decent i7. So my render times will seem pathetically slow becase, well, they are!

    On 3DL versus Iray: the process is different, to be sure. But because I come from a photography background, even going back to chemical darkroom stuff in the late 60s, I'm more comfortable with non-biased renders, setting up lights, and so on. I have not used Octane other than a quick trial, but if it works for you, then the expense might be worth it. You might also try Reality. I have it for both Poser and D|S. It does a nice job, too, but you still have to light things carefully.

    With Iray, you can still construct an environment and light globally. Assuming the walls of this room are white, use it as a giant uber environment. Render times are going to increase, but it might have the look you're going after. IThink about how it would look if it were a real room. A 3- or 4-point portrait light setup in the middle of a big room is going to leave shadows in the deep background. Your Iray scene will be no different. 

    That said, have you tried making those back walls slightly emissive? 

    Thats a very interesting idea and not one I've thought of before. It might work really well in a white-walled room. Unfortunately the walls, floor and ceiling of the room I'm using are very dark (its a space-ship cargo bay - in fact most of the sets I have are dark sci-fi rooms), which is probably contributing a lot to my problems but I really want to use the set. Plus I've seen sci-fi renders done in Octane where the walls are virtually black and the room is still lit incredibly well in all corners, with excellent ambient occlusion, by a few wall and ceiling lights so it must be achievable somehow (though maybe only in Octane, not Iray).

    I think I'm going to play around with adding more lights, but each of them at much lower levels... maybe that'll help, if I can just find a way to stop the shadows looking so horrible.

    I don't feel that sorry for you - I'm running on a 660 GTX card, which is acceptable I guess, but with only an i5 CPU cheeky. My last render took over 5 hours.

    Post edited by tl155180 on
  • ToborTobor Posts: 2,300

    Iray has trouble with dark scenes. You may find it better to over-light to give Iray plenty of photons. You canuse a canvas (click the Advanced tab in Render) to save out to an EXR file. Turn tone mapping off in D|S. After the render, open the saved EXR in Photoshop (Image->Adjustments->HDR Toning), and tweak the tone mapping from there.

  • tl155180tl155180 Posts: 994

    Its ok, think I've nailed it now thanks. I took away the brightest wall light at the near end of the room and turned down the ceiling lights, then attached a softbox spotlight to the camera (off-centre) to pick out the figures more attractively. The ceiling lights are now the brightest lights in the room and cast the most noticeable shadows (which feels realistic), while the camera spotlight is acting like a bright fill light and the wall lights fill in the rest. Its not quite portrait lighting, but at least the light levels will be pretty even no matter where my figures are in the room. And the shadows are starting to behave themselves now laugh.

    Thanks for all your help.

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