Iray light question
Nosiferret
Posts: 330
in The Commons
I am just getting into the iray stuff and I usually start off with light sets. I'm looking at what is in the store and frankly, I'm going cross-eyed. I can't decide which one to try out and I don't have the funds as I used to to just pick a up a few to test them. So I thought I'd toss out the idea here to get some feedback on which light sets for iray is worth the $$ for portrait and small size renders [as in nothing huge, like outside environments, etc]
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What types of scenes do you plan on rendering (i.e. portraits, landscape, sci-fi interiors, home interiors, etc)?
Why do you have to spend anything?
For a couple hours worth of time and a few 'save as' you can grab a few HDRis, plug them in and create your own presets. Using a decent HDR, not much else needs to be done (maybe an additional light as a 'sun' if the shadows aren't 'good' enough).
There are even 'point and shoot' 'studio' HDRIs that have the photo studio lighting...just add backdrop and render.
I strongly recommend any of the Dimension Theory Iradiance HDRI sets and Dumor3D's Apocalyptic Plant Outdoors Set. There are other sets that include parametric lights and mesh lights, but the real "meat and potatoes" is in the environmental HDRI-based lighting. You can always add the DAZ Iray Uber Ambient shader to a primitive to make your own mesh light, which I do all the time. The sets I mentioned are great for backdrops or just for lighting if you turn the dome off. Inane Glory's IG Iray Essentials are also very good for portrait and interior lighting.
I'm with mjc. The included "Ruins" HDR, and maybe a couple of the freebies in his sig line, plus the included lights with D|S, are all you really need. I've purchased some of the sets, but all were unnecessary. I got them to learn from, but in the end, I discovered more here, and on my own, doing tests and reading up on various Iray topics. Save your money unless you're going after an HDR that you always want to use as a backdrop (just remember, a thousand other people will be using that same backdrop in their renders, too).
The simulated studio images at:
http://www.mrbluesummers.com/category/downloads/downloads-textures-materials
are pretty good if you want to do portraits. The HDRi's include 3-4 point studio lighting rigs, properly positioned. You might find, as I did, that the key isn't as bright as it might be for some types of shots. No matter. You can either edit the HDR if you know how, or you can simply bring in an extra spotlight.
Speaking of spotlights, there's a "secret" to using them for getting much better results. Spots are simply a catch-all lamp for multiple types of lighting Iray is capable of. After adding the spotlight, change it's type from Point to Disc or Rectangle, then enlarge the emitter. The larger the emitter, the "softer" the lights (and therefore shadows). The units are in centimeters. You start to get soft nicely shadows at about 20-30 cm.
Another very nice studio set is the Redpec set (linked from the deviantart page...link in the HDRI list).
I recommend Inane Glory's Point and Shoot for Iray, mesh lights.
http://www.daz3d.com/inaneglory-s-photo-studio-point-and-shoot-iray
You get numerous light setups as well as individual lights, with pointers already attached to them so they are easy to place.
Except that mesh lights take longer to render than spots..
Yes, indeed. People got all excited about mesh lights because of their use in Lux Render and other PBRs, but they're largely not necessary for scene illumination in Iray. Iray has its own built-in light sources. You can use a huge spot as a light source and it'll give out the same kind of light the mesh will, but more efficiently. What's more, you can "aim" through the light, something mesh lights don't let you do.
Meshes can be easier to tug around because of their large shape and size, but if you need that, simply parent the spot to a plane. If the plane shows in the scene, hide it (you can also hide the spot emitter from the renderer, as well). Can't do these with mesh lights.
Need broad, soft light? Turn that parented spot around, back it up a little, and aim it at your mesh. Texture the mesh with white shader, matte or gloss, depending on the look you want. Tinge it with gold color to warm up the scene. Now you've made a great reflector. Want an umbrella light? Find a freebie umbrella prop (find one that has a parabolic shape), parent a spotlight to it, and texture the umbrella. You've got a $2500 Norman umbrella flash unit!
There ARE practical uses for mesh lights, especially as in-scene props, neon signs, clothing effects, and SFX illumination. But they are not needed, or really even desirable, as a substitute for lighting a scene.
Especially since Iray handles bounce cards remarkably well. Mesh lights, in Iray are really just accent lighting.
When I'm going for soft shadows, I find that a large mesh light is faster than a spot with a translucent screen, but that could be because of my particular rig/gpu. And you can, actually, hide mesh lights for most purposes. If you use the Advanced Iray Node Properties script, you can turn your mesh object into a Matte object (shadowcatcher) and by reducing the opacity to something very small, the mesh light is virtually invisible. I suppose a very dim Matte mesh light surrounded by objects in a very bright scene might accidentally catch shadows, but I've used the approach quite successfully.
Why do you need a transluscent screen to make a softer spot? Just increase the emitter size. In real life you'd use a transluscent screen because your actual light source is small. You don't have that restriction in VirtualWorld, and increasing the emitter is functionally the same from a lioghts physics standpoint. It's also more efficient because the light doesn't have to be calculated going through a transmissive material.
I'll say it again: the quality of the light from a large emitter spot is the same as it is from a mesh. The difference is that Iray doesn't have to deal with calculating light origins from a geometry, and can merely render from one of its own internally defined area lights (that's all D|S parametric lights are; they connect directly to Iray light types). I don't see the need to futz with matte modes and opacitywhen the solution is already built into the engine.
The purpose of a diffuser, in real life is to change the size of the emitter. In effect the diffuser becomes the emitter, rather than the light bulb. Think of the spot or point light as virtual bulbs. Since the size and shape of the virtual bulb can be changed to mimic the size of the diffuser, there is no need to actually create a virtual diffuser to get the same result.
Always more than one way to do something. :)
Absolutely! One thing I'm working on is gobos and patterned diffusers for Iray. I personally don't have the GPU-horsepower to pull off much off it, especially when using caustics, so I'm playing with a couple of tricks.
Don't also forget that spots (and mesh lights, for that matter) accept IES profiles as inputs, useful for shaping of lights. IES files are just text files and use a simple declarative table for defining the lobes and shapes. You can play with these to create light designs of your own. You can also download this program:
http://www.photometricviewer.com/
for a visual depiction of the IES profile. I haven't done it yet because I'm chicken (cluck, cluck!), but if anyone has run this without malware alarms going off, let me know! I'm over cautious about such things. (Fake versions of this file are said to contain viruses, but this version looks clean: https://www.virustotal.com/en/file/1562bf953fb7ccf84cee85efd5417a73b3651f813a0966bdbcff0f7f221df2cd/analysis/)
I've been using zbyg's HDRI set: http://zbyg.deviantart.com/gallery/6278123/Resources along with added spotlights as needed, changed to disc/rectangle geometry and made bigger as mentioned above.
The problem for me with photometric lights is in visualization. The little spiky thing used to represent a light in the preview bothers me. (Bothered me in 3Delight, too, but there wasn't anything I could do about it there!) In Poser, you can make a light invisible without turning it off, which you can't do in DS. I think that's why it bugs me so much. Making an invisible mesh light produces the light I want without interfering with my view of the scene. I don't doubt that you're correct in saying that a light renders faster than glowing mesh, but I've honestly never noticed a difference. Maybe it's due to my rig or the simplicity of my scenes...?
I actually DID forget about that, lol. Thanks for the link.
Wow -- awesome resources.
In my sig...there is also an IES links list, along with the HDRI list...
The 'Artist Freindly' collection has a nice, labled preview of what each light looks like.
As I'm sure you know, the "spikey" things can be turned off by adusting Display/Opacity Scale. I don't mind that lights always show when they're on. To me that's a good thing. In shooting real-life, knowing where the lights are, and which ones are active, has always been important. I have long wished D|S had a Poser "world view" the of lights and their relative positions and colors.
LOL, Nope -- I did not know that!! Never even occurred to me to try that, duh. Ya learn something new every day! Thanks for that tip!
Ultra-Genesis-Studio-Vol-1-Box-Lights over at rundnatime if you need help with lighting.
However, why not just learn how to light? Play around and see what does what. Also, mesh lights work really well, don't ignore them or trade for spots. Spots are great, all forms of lighting have their purpose and place. Mesh lights (planes with a curved deform or just flat) produce wonderful soft light akin to a Kino Flo. Also, you shouldn't have to worry about turning lights visability on/off or being visable in your scene - in the real world, you would place your lighting outside of your frame and everything would be lit properly (meaning, the lighting is what you want without lights in your frame). Don't be lazy just because you can be.
There seems to be ongoing misunderstanding of "spotlights" in D|S. For Iray, a spotlight is a universal lamp fixture, and morphs to most any type of light you want. When the emitter is changed from point to area shape, it is no longer a spotlight, except in name. Adjust the size of the emitter and you have that Kino Flo, but far more efficient, because it's an internal light source. nVidia advises against using the traditional mesh light approach, as it's not needed; leave meshes as principle light sources to those renderers without robust internally supported light types. The main problem is this: separate light calculations are required for every polygon in a mesh, even if it's flat. For a low-res mesh it's not too bad, but these types of "lights" can easily take 5X-100X longer to render, depending on their size and geometry.
In the "real world" there are very few wall-sized lights, so the comparison isn't valid. As much as possible, we like to place our lights once, then move the camera for different shots, something many of us do. If we're constantly resetting the scene to get bulky lights out of the way, not only does it take extra time, it changes the lighting shot-to-shot. Mesh lights are certainly appropriate when they are a part of the scene.
Yeah, I had a scene with modern lamps, with those compact flourescent lights, the ones that look like little spirals, and my first approach was a very straight 'make lightbulbs into emitters.'
That... was horribly slow on a fairly modest scene.
But the bulbs were behind shades, so you couldn't see them at all... swapping them for point sources with sphere geometry? WAAAAAY faster.
Corollary to that...if you are going to use a mesh light...use the least number of polys you need to give a 'shape'. A single poly plane, as emitter, on single sided, is going to be about the fastest mesh light you can make.
You're all undoubtedly right about the speed of a light vs. a mesh emitter -- makes perfect technical sense -- but I just did a little testing and (on my rig) using a low-poly sphere mesh light, a 1200x1200 px basic scene rendered a whopping 9 seconds longer than a photometric light at the default moderately-crummy quality settings. (Basic scene = a few walls, HDR environment base, a human figure, some furniture, nothing with refraction or complex reflections.) I'd post the pictures, but in the interest of haste, I didn't clothe my models, so it'd break the TOS. Anyway, I'd say my PC is "upper-middle-class" (i7 3.5GHz ivybridge quadcore, GTX970 render GPU, GTX670 running displays, 16GB RAM) and I'd say most of my scenes are fairly simple. I'm an unashamed NVIATWAS renderer who now dabbles in photorealistic "fashion model" scenes. (Fluff. And I'm okay with that!) I pretty much always use an HDRI environment (not always used as a dome background) and a few supplemental mesh lights. Maybe I'm fond of mesh lights because temples (of NVIATWAS fame) generally have lots of opportunities to showcase "glowy things." (Magical crystals, radiant orbs, interdimensional portals, holy weaponry, etc., etc.) So, I'll stand by my assertion that one shouldn't dismiss mesh lights off-the-bat.
I do appreciate the info I've learned here, though. It's amazing the amount of collective knowledge one can find in these forums!
9 seconds doesn't seem like much...but multiply that by more lights or more complex geometry and you can see where the savings will pile up. It's also not quite a linear progression...doubling the number of polys on the sphere may not double the time, but it will raise it some (there is a chance, I haven't done the numbers crunching, but it could actually quadruple the time!).
If the meshes are working for you that's all that matters. But the main point is that Iray doesn't need mesh lights for scene illumination. The Iray engine supports native light types that perform the same function, and have fewer failure points -- things that an unsuspecting user might misdial and end up with a horribly slow render.
So, anyway, I'll ask again about the Photometric Viewer I mentioned above:
http://www.photometricviewer.com/
Anybody tried that yet? Is the file safe? Apparently there are versions of it packed with some nasties. I'm guessing the file from the author's own Web site is okay...
The thing about Iray is, the more lights, the faster the render. Don't think 3DL ;)
10 minuter render with mesh lights only.
so far the ones i found most fun was total iray lighting..mainly the spotlight is pretty nifty to play with. and the "real lights" for iray is very handy in quickly lighting up a scene realistically.
Yes, that version should be fine...
You could always submit it here
https://virusscan.jotti.org/