HDRI and indoor scenes
Steven-V
Posts: 727
OK folks... I have been beating my head into a wall for the better part of a week trying to get a lighting scheme I am happy with for an indoor scene. Outdoors, I love using HDRI, and it works great. But indoors... the walls get in the way. I am using Room Creator 2 with a particular set, and there does not seem to be an option anywhere to turn off "cast shadows," which used to be the trick I would use to allow light to "pass through" walls in pre-4.8. I don't know if this is an Iray thing or a 4.8 thing, but the "cast shadows" toggle seems not to exist anymore under Parameters/display where it used to be. Nor can I find it anywhere else.
So how exactly does one go about using HDRI in indoor scenes? I know I have seen it done before, but when I try to do it, the room blocks the light. Do you just take out the walls that you don't need, the ceiling, etc? I mean, I know I can do that, but it seems like this defeats the purpose of HDR lighting, as all lighting coming from the visible walls will be blocked, and this will negate the "light coming from all over" effect.
I am guessing there is a trick to this, but I can't figure it out, and searching the forum turned up no results for obvious search terms.
Thanks!
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Comments
Several tricks.
One is to use windows...you set up your room and any windows or doors (open) you use a glass shader on that will allow the light to come through. One drawback to this, unless you have enough of them or are doing scenes during the day, you aren't going to get enough usable light without resorting to very long render times, supplemental/accent lighting or 'overdriving' the light coming in from the outside. Most renderers have some sort of 'portal' feature to make this easier...not sure how to set it up in Iray, though.
Another is to set up the 'room' and light it in the 'traditional' manner...with mesh lights/physical lights/etc...and then create a 'mirrored ball' or cubic render and create your own backdrop image/hdri. Then set up your scene, minus the 'room'...using your self created images. This makes a two pass render, except that you only need to do the 'space' once.
Of course, you mentioned removing parts. One of the tricks for that is to find the least important parts for the scene and remove those.. You'll still get some bouncing, especially if you are using 'studio' lighting type hdris that you align to 'fill in' the missing geometry. This one actually works pretty well for things like stores and such that you expect most of the lighting to come from the ceiling.
And one that works well for large rooms...just act as if the space is big enough that the hdri is 'all inside'. This is sort of similar to 'make your own' of the scene you want to use...but more generic.
I'm sure there's probably more...and several ways of doing each of those suggestions...but my favorite is the windows one. In many ways, it's the easiest, especially when you don't stick only to hdri lighting. You know...any table lamps, candles, etc, within the room turned on/emitting on their own.
And some of these techniques were 'perfected' as stage/set lighting...the keep the walls/replace the ceiling with a light grid is a commonly used set lighting technique....
Setting the HDRI "outside" the scene and using windows does me no good. In this particular scene, which is a hospital room, there is only one window. I already had a direct sunlight going through that window and it looked OK.
I feel like the image seems too "flat" with mesh lighting, so I was hoping doing HDRI would make it pop a little more. But it seems like doing this is not really practical for an indoor scene. Which IMO is a huge limitation, since the HDRI lighting is such a great feature otherwise.
Well, most hospital rooms are lit from the ceiling.
So a big mesh light on the ceiling or turning some fixtures on the ceiling to emitters to add to the window would probably help.
The rooms on the ward my wife works in have combination of fluorescent recessed w/diffusers on the ceiling, a few recessed 'can' lights over the bed and trough lights, about a foot/foot and a half below the ceiling, pointing up to bounce off the ceiling. It's an OB ward, so probably not typical for a medical/surgical ward.
Using lights with attached IES profiles work great for the cans...and if you look I've seen profiles for the tubes and diffusers, too.
Also any equipment will have indicator lights/screens...those can easily become emitters, too.
Now, one thing to remember...most hospital rooms are lit to make it easy for the medical staff...not to look good/dramatic. So, yeah, in real life they tend to look 'stark', flat...even harsh. And when all the tubes are on, the rooms in the OB ward are just like that, too.
Hi Steven,
I have to agree to mjc.
Depending on the number and size of the windows there is more or less light entering a room.
And you have to keep in mind that there is a big difference between "photometric" and how our brain processes the picture we see live with our eyes. This is a realy surprising effect when you start with photography.
"The scene looked for me very different to what my camera shows .. ??" ;)
I posted two examples on deviantart for day and night.
http://andysanderson.deviantart.com/art/Fashion-in-Bungalow-DayLight-iRay-537512576
http://andysanderson.deviantart.com/art/Fashion-in-Bungalow-Night-iRay-537514333
As you see, with iRay it is very easy to let the real light emitting zones of your lamps acting as an emitting device.
For the daylight scene I selected a higher value for "gamma". But it depends on your taste to play with the parameters for shutter speed, F/Stop, ISO and Gamma.
But now a different question:
You talked about the successful use of HDRIs for outdoor. Which ones did you use? I tried different available on the web. But none of them worked.
Only the default one. But the "sun light" out of it is not really satisfying.
Where did you get yours from?
Andy
I got some free ones from the links SickleYield provided.... and from somewhere else I no longer recall, unfortunately. The one I was most happy with was an outdoor shot of a city from atop a helipad. Very nice sunlight and good tonal values.
One of the problems I'm having is not the amount of light but the quality of how it is lighting up the scene. It even seems to be affecting the way the character's skin looks. For example, here are two renders. I turned everything off in the scene and zoomed in on the face. First render is with the default HDRI that comes with Iray. I love the way her skin looks in this shot. Second scene is with 2 mesh lights. Notice how much more orange her skin looks? Her also looks flatter. Yet I did nothing to her at all -- I did not change anything but switch from dome only to scene only.
Now, I did not mess with the mesh lights to make the angles perfect, I will admit that... but the HDRI gives so much more even, graceful light, I really would like to use it indoors, but doing so does not seem possible. And the frustrating thing is, it would be if only I had the option to tell the walls not to cast shadows, like we used to have. Argh!
My issue here is not exposure or even shadows. It's that the mesh lights are having a dramatic effect on the "skinning" of the characters... skin surfaces that look like skin in HDRI look more like plastic or rubber to me in mesh lighting, even when the character's surfaces have not been altered at all. It just seems like there is no substitute for HDRI, and I was hoping that there would be some trick to getting HDRI to work on an enclosed set. But since there isn't... I guess I will have to keep playing around with it.
I confess at this point, I am strongly thinking about just going back to 3DeLight. I've been screwing with one panel in my comic for over a week now. In 3DL I'd be on the next page of the comic already.
Yes, the main light is a mesh light overhead. I tried turning a flourescent tube light into an emitter but for some reason it increased the render time by almost double, so I switched to a flat plane. The quality of the light did not seem much different and it rendered 2x as fast.
Hi Steven,
Hm, in studio photography they use softboxes, which are comparable to "mesh lights" to make the plasicity and the contrasts of the models look way softer. And this is what happened in your scene, too. If you want to have it comparable to outdoor (hard sunlight) you have to use extra spotlights.And the question of color: It depends on the color-temperature parameter and surface color you used for your mesh lights. So shift it to temperatures > 6500 K.
I don't know if the spotlights of omnifreaker or AoA are still working properly. Are there new ones for iRay available? Of cause included in the basic DAZ 4.8 setup, as the old ones were.
Colored lights always change the way things in the scene look. Imaged based lights are by nature colored by the things that the image are of. We don't always notice all the color reflected on and around us in the real world but it is there. Iray also will pick up colors used in a scene and include them as part of the colors that they start bouncing around. I have been doing promos for a floor product and in some cases the color from the floor is very clearly impacting the way the near white walls are colored. If you wanted no color interference you would have to do what photographers do and create a white space with as little non black or white in the room as possible.
Funnily enough, since it's a hospital room, most of what is in the surrounding room is black, white, or a shade of grey. So it is surprising to me that there is such an impact on color.
Additionally, the second picture I have with the mesh lights was done in an empty room with two white colored, 6500k temperature lights. Plus it is not only affecting her skin color, but also its apparent translucency and SSS.
I'll try making the color temp higher than 6500k, although in my experience in other venues, e.g. monitors, going higher makes things look very "blue".
Sickle's tutorial is here: http://sickleyield.deviantart.com/journal/Tutorial-Lighting-and-Tone-Mapping-In-Iray-531864617
Also, I am not 100% sure but based on a video tutorial I think was posted by SickleYield, I think Sickle is a "she". :)
Hi Steven,
thank you.
Yes, she is.Indeed she is.
Found it !!! if you set render mode to Interaktive instead Photorealistic, the Cast Shadow Option apears again for erverything .:-)
Hm. I had not thought to try that.
Does it have any effect on how the render looks in terms of quality?
For interiors Tone Mapping (real world camera settings) is the key. Set up any mesh light fixtures to real world lumens output and Kelvin scale and adjust tone mapping to suit interior shots. There are plenty of sites that can help with understanding real world camera settings. The beauty with cameras in DS we don't have to worry about camera shake when taking the shutter speed down past 60. ;)
Hm. I had not thought to try that.
Does it have any effect on how the render looks in terms of quality?
yes it is not good as the photorealistic setting and i have massive problems to render eyes with the light settings -.- today i tried hours to figure out watt happend with the black/dark eye thing:down: the results were good in my opinion but this bug(?) drive me crazy