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It's also worth noting that very diffuse light sources and a good light level is, IMO, best for rendering dark scenes ... because you can then darken it to your liking and it doesn't take eons to render. (The diffuse lighting helps create the effect of low light levels amped up by your eyes/camera)
Oh wow i was under the impression that with an unbiased render engine you would just place lights like you would in real life (so you just create a "sun" light and it lights the scene accordingly) and kept it moving. I didn't realize you had to do "tricks" like in 3Delight
404nicg: You CAN do that, and it can make the learning curve easier.
But consider how much in real life photographers manipulate light to create effects and bring out details.
Nvidia call Iray a photoreal render engine meaning photo like and not what we see through our own eyes which is way Tone Mapping is an integral part of the process.
Valid point..but if iray is physics based and designed so light behaves realistically, why wouldn't light shining through a window illuminate the entire room like it would in real life?
It does, you only have to tweak the tone mapping settings, rotating the dome so light comes directly through the window also helps.
Both "lonely church" and "suite" in my gallery are lighted with sun/sky only if you want to check some results.
What Rafmer said. My comments were along the lines that there are realistic things that happen that often require help to light things well. Also, if you aren't rendering HDR images (which Iray doesn't, by default, but you can experiment with canvasses and exr), the tone map of the image is limited. That is, the range of light to dark is small, compared to what our eyes and many cameras can handle.
Our vision has all sorts of filters to make what we see into usable information, and part of it helps 'brightness correct' what we're looking at. Which is neat -- how the visual system in our bodies/brains work is fascinating.
Think of it this way...the camera in Studio has no automatic exposure features...it's purely manual. And just like a real camera, there is no one setting to cover every lighting situation.
One thing though, you don't have to worry about blur from long shutter times or grain from high film speed.
If you enable nVidia Iray preview mode in the viewport there is an exposure control, next to the drawstyle picker - click, then click on what should be a well-lit spot in the scene.
On this topic...I was thinking of a lighting a big area with essentially large neon tubes...I was gonna make a column primative or 2, and set it to emissive and place it where it'd be in the scene.
Is this a bad/slow idea? Should I just have the columns there as props, but use something else for the actual lighting?
What kind of "side" number should I have for a column? I figer segments should be 1, I know the less polys the better, right?
You can set point lights with geometry. This is more efficient than creating the geometry yourself.
Do the point lights show up as a thing? like a tube of light? :)
No they don't, and that's something I'd really like to see added to the light features. It isn't always obvious which way "up" any non-spherical light geometry is going to be when you render. Something for a feature request, maybe?
So best to make a tube, color it to look right, then use a point light to illuminate and hope I get it to shape and size and position right?
Best to use a point light, set the Light Geometry to a cylinder, and adjust it accordingly.
that would give me the light, right? But I'm also needing the on stage element.
In iray, once light has a geometry, it's visible. If you make it a cylinder, you see a glowing cylinder emitting light.
I see.. Interesting!
Changing the scale of the cylender, I could make it longer, but the light didn't seem to change any (like in different places...do I need to experiment more, or does that matter?
I've had pretty good luck with point lights as fluorescent lights using a suitable IES profile. With a profile set up, it probably doesn't matter to performance whether the point is set up as a plane (which might look odd from some angles) or a cylinder, since I would expect it to cast light rays the same regardless. Or would it?
Scavenger: I forget right now how point lights work vs. emitting primitives, it could be that total luminance (amount of light coming out) is preserved.
With actual emission objects, you can set luminance by a total value or a value per surface area, depending on units. I don't think you set that with lights, I think you're stuck with the same amount of light regardless. Now, a long light vs. a short light will look different and scatter light in a somewhat different distribution.
Gotcha! could you point me towards which settings to adjust in the tone mapping?
Mostly Exposure Value is the one you are looking for; the next three (just below EV) relates to this one so play with all four to get your desired look.
You can start by increasing the ISO. From there you can start adjusting the F-Stop and/or the shutter speed. Larger ISO = more light in the image. Slower shutter speed = more light in the image. Larger apterture (smaller F-Stop) = more light in the image - this one is tricky in terms of determining the correct input as F-Stop is a ratio in which higher F-Stop means less light/smaller aperture, Studio handles this by expressing the F-Stop parameter input as the denominator of the ratio, resulting in the input of a larger number to the parameter creating a larger apterature/more light as the resulting ratio is a smaller number. Put more simply, in Studio, inputting a larger number into the F-Stop parameter results in a larger aperature/more light. F-Stop also can affect depth of field.
Some typical ISO values are 100 (the default I believe) 200, 400, 800, 1600. Use the lowest ISO setting you can and still have the exposure level you'd like. For your interior shot, you could start at 200 and adjust from there.
Seems to me that the effects of ISO/Shutter Speed/F-stop are all the same as far as the actual render is concerned, and one can stick to just one of them (ISO being the most intuitive; more=brighter) and tune to taste. On the other hand, there are five gazillion photography sites that give advice on the corresponding SLR camera settings for various real-world lighting conditions, which are applicable in Iray. If your lighting values also correspond to real-world light flux, of course. Photographers will select shutter speeds and f-stop values to affect motion blur and depth of focus, neither of which are affected (at present) by the corresponding render settings in Iray, Still, at least you can get good numbers from these sites.
Generally, with film, increasing the speed of the film (ISO number) increases the 'grain'. That is not a problem with rendering.
Making the shutter 'slower' increases the chances of blur, due to movement (camera or subject)...again, not a worry in a render...so upping (slowing down) the shutter to more than 1 second isn't going to matter, other than the amount of light.
Same with f/stop...
Really, the two relevant issues with tone mapping:
Enough light to render well. If it's dark and you crank up the ISO, it's going to render like sh*.
Consistency. If you have a robot with glowy bits in one render and the same robot in another render, you should use tone mapping more to adjust 'realistically.' So your robot's glowy bits look bright indoors, and dimmer outside, and you use tone mapping to adjust apparent brightness to look good.
One thing I've noticed when playing with tone mapping is that I often have to turn down the saturation quite a bit as things look SO saturated that it looks so over the top with color. But when getting the skin looking really good I noticed that other areas of the render look washed out by brightness. I wish there were some very balanced settings for interiors and exteriors that one could study to learn what works best. I swear, I love iRay but the amount of work to get things to look right have trippled, it's not about loading a set of lights and making sure your bump and displacement maps are set up correctly.... it's just so much more work. I'm slowly getting it for the most part but it is a bit frustrating when test render after test render ends up taking hours out of my day. Just saying...........
That shouldn't be happening...
Iray demands a linear workflow, if you are not using a linear workflow, then that is the kind of problem to expect.
Hi,
Can you elaborate on the Linear work flow a bit more as I'm not understanding that.... Thank you!
Here's an article from Nvidia
http://http.developer.nvidia.com/GPUGems3/gpugems3_ch24.html