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3DL is the opposite of Iray in the dept of lights. More lights speed up Iray, more lights bog down 3DL. When using 3DL one must be more "creative" with lighting than just putting a light everywhere a "light" is indicated. A chandelier, for instance. In 3DL it is crazy to put a point light into every "light" or "candle flame" because it will greatly increase render time while not giving the results that one would think it would. The chandelier should be handled as a single light if it is lighting a large area, or a system of a few brighter lights that can show different light directions if desired. With Iray, each additional point light actually helps the engine resolve the details and speeds up the process.
One must take the technologies into account when deciding where they want to go. Throwing out an engine "just because" is not wise.
Kendall
@Will: that looks really nice ! :) I like it much better than the first one.
Laurie
...but if you use emissive lights (one of the attractions to Iray as you don't have to manually "place" individual lights everywhere) the opposite is true. Case in point, that chandelier. For the scene I set up in Magnus Manor, I originally made each bulb in the near chandelier an emissive light which basically caused the render process to almost grind to a halt. When I changed the camera angle to exclude the chandelier in the view field and placed a single cylinder emissive light where the fixture was in the scene, render speed improved.
It's complicated.
Emissive lights need to be on simple objects, or they consume a lot of render time. You need a lot of light, until you have enough and then more stuff can slow things down.
In the case of my 3DL render, normally I'd prefer to have off-screen light sources to diffuse into the scene. But... I wanted that look of candles shedding light. So it was worth it to take the hit for a better look, I think.
But yeah, my stance has been for a while that there are a wide range of tools and factors that combine to drive a work in different directions. I think 3DL and Iray both have a bunch of positive and negative elements that depend highly on what you are doing, and your set up.
Like right now I'm trying to do another yarn scene in Iray and I'm finding that the displacement detail I need just ends up sucking WAY too many resources, and I'm going to have to shift everything over to 3DL.
This annoys me. But hey. At least I have the option.
Setting geometry to "emissive" is not adding a light. Every facet (and its normal) in the emissive geometry has an overall effect on the lighting profile for that piece. The more complex the geometry, the harder the calculations. Setting a bulb that covers almost a complete sphere(oid) as an emissive is insane. Use a point light there, that's what they are for. This is simple physics that one learns in high school.
Kendall
...however, then I may as well just stick with 3DL where I have to do that (if you don't use Uber Area Lights which also have a heavy impact on render time).
The basic concept of using a mesh light to turn a flame or a light fixture into a light emitting source is by itself elegant compared to having to manually place lights and increase ray depth to shine through fixtures and shades (which also can slow down rendering as well) so they look correct and illuminate a scene properly. For "off camera" lights, yes photometric lights work well, but, say you have several sconces on the wall which are seen by the camera. Turning the flame, bulb, or fixture into a light emitter makes more sense.
In the case of sconces, I would recommend that the Ambient be turned up to get a "glow" along with a photometric light to provide the actual illumination. For fires, emitters are absolutely the correct solution since the irregular shape needs to be lit. However, even here one must realize that for singular flames the vast majority of the emitted light is from a single part (http://www.slideshare.net/grovervijayk/model-lesson-on-parts-of-flame-by-vijay-grover) that can be emulated using standard lighting and not emissive geometry.
Kendall
For a light bulb, you don't really want to turn the whole thing into an emitter, anyway...it's just the filament (on an old fashioned incandescent) that emits the light. And that can be done as a single one quad rectangle, buried inside the bulb...but it would need, DS terms, a clearly defined and accessible material zone. Same thing can be done with florescent tubes and even LEDs. The only time you really need the 'whole' thing is for large fires. And simpler is better.
For things like display screens, again, a single quad is all that's needed.
And single quad 'mesh' lights are just about as fast as photometric points (even in 3DL with UberArea simple geometry is significantly faster).
....OK but what about florescent light fixtures with bare elements, neon signs, or a bare light bulb hanging from a cord in a room? Certainly you want the light to be cast in more than one direction for it to look accurate.
Most light bulbs and florescent tubes are also frosted and would render dark if you simply put a light inside the geometry without boosting the ray depth to the point it would slow down the process.
Shaped neon signage is one reason that emissive geometry was created. For a fluroescent light (CFL) then you can use the same method as the sconce I mentioned before: Turn up ambient to emulate glow and centralize the light from the center of light mass (not the same as the total center of mass). A hanging bulb on a cord is still a point source. Any high school physics text will help here.
Set the bulb geometry to not cast shadows, place the light source(s) outside the geometry, or set the diameter of the light origin to fully encompass the bulb -- depending on the engine and extensions you have loaded.
Kendall
...setting a point light outside will often illuminate the geometry of the bulb and other fixture elements incorrectly. I used to wrestle with this a lot and ended up reducing the opacity of the bulb, turning off shadows for the bulb, placing the point light inside it, and cranking the up ray depth. For florescent elements and flush lighting in 3DL, I just consigned myself to endure the glacial render time of Uber Area Lights.
Again this seems to be stepping back to the 3DL technique of having to manually set up and place arrays of point and spot lights thus negating of what I feel is one of the advantages of the Iray engine.
Jumping into setting everything as emissive geometry is a hack; one that you'll pay for dearly in performance during render. There are certain basics that are the same regardless of engine used, placing correct lights and types where appropriate is one of them. Iray also has the ability to use industry IES profiles for lights that accurately provide the "real" lights with real-world attributes. Using these can go a very long way to making scenes look proper.
Kendall
....well it apparently comes down to either more setup or more render. time. Creating mesh lights may be a "hack" but it allows for surfaces that are supposed to emit light to do so on their own without a lot of tedious placement and messing with settings/profiles to make light appear to be emitting form the actual source rather than next to, or above it, or below it (or whatever). Again for off camera lights, that is a different matter.
As to IES profiles, I know there is something here in the store that deals with them, however I haven't purchased anything in months as I am on a tight fixed income (partly why I continue limping along on only 10.7 out of 12 GB of system memory and a GPU that isn't powerful enough to even render a simple portrait on). Iray looked to be so good until I began working more with it and realised that I need more system than I have to get a reasonable amount of performance out of it.
"Iray also has the ability to use industry IES profiles for lights that accurately provide the "real" lights with real-world attributes."
That one is a "yes, but" due to the xyz of Studio.If the light is modeled correctly for that then they do work wonderfully. If not they will shoot toward the Z instead of Y. Unless of course something has been changed recently and no one mentioned it.
In 3Delight you can fake tanslucence by using a Shader Mixer shader to test the ray type and use a lower opacity for light rays than for other types, thus allowing light out of the bulb without making it unduly see-through. That was my standard fix for lampshades, which were very hard to get right otherwise (and generally ddin't use compilcated shaders, so there was no great loss in using a simple Shader Mixer shader).
I would be interested in learning what you are describing. Lamp shades really bug me, lol. As do bulbs. And those tutorials just stress me out.
Agreed. More info on how to do this would be awesome!
I've put a shortcut on my desktop to remind me to do a quick tut.
Awesome! Make sure it's geared for dummies like me. I get so impatient with all the techno-babble most tutorials has because they try to explain the stuff I don't need to know. I just want simple. How do I do this or that. Not why, lol. Make sense? Plug-n-play kinda stuff.
...using the shader mixer is not simple though. As I have mentioned, it looks like a basket of tangled yarn to me.
Yes, please!
Kyoto Kid: the shader mixer is not that difficult. It depends on the complexity of the shader ... look at my Velvet Shader: http://www.daz3d.com/forums/viewthread/25560/
...I understand the Carrara shader room fine, plus I can see instant results in the preview window as I am working. Never could quite grasp the node style of mixer, either here or in Poser as I feel I am just guessing at things half the time.
Will, thank you for the short tutorial; I'll try it. Maybe you should send it (and more of your fine little tutorials) to DS Creative! I am very glad this magazine reappered!
Where's the tut? I missed it :(
And DS Creative came back? Awesome!
Of course ... another awesome-looking product only for iray:
iREAL Animated Ocean Water System
Ocean Wide
For 3Delight...doesn't animate tho.
Laurie
I've seen people animate in daz, but regardless, it's also good for stills in the description.