sperical envsky vs. IBL

[surf]

maya & mentalRay
is this two things comperable?
I got to know that env.sky does not work as the base of lighting. it was good to use, because I could easly transform it.
IBL is good for lighting, but it is hard to transform it.
together they do not really work. (or I could not manage them)
which is the better solution for lighting and background functions too?

[Greggl]

I'd start with the standard lighting, built in the package. At this point, the
envrionmental lighting tech is overkill for MOST projects.

Use 3 point lighting techniques and make sure your ambient levels are dropped
down so as not to wash out the overall look.

[im.thatoneguy]

A little trick I picked up. If you need to accurately match the lighting in a scene and you have an image probe already, load it up as an IBL in the scene.

In Photoshop adjust the exposure so the image is pretty underexposed. Save it as a standard Tiff.

Replace the HDRI image with your tiff.

Now you can look around the scene and create the essential lights looking at the world, as if you were standing next to your object.

You probably won't have more than 2 or 3 light sources in any outdoor scene, and you can pretty accurately judge the relative intensity and distance of indoor lights by just sliding around the exposure slider on your probe if you need that level of accuracy. Where I'm trying to match tall narrow objects with lots of overhead lights that can be a real time saver in trying to reconstruct the lighting in a scene. Especially if I'm not given any lighting notes. It's suprising easy to give somebody a little shiny sphere and say "please point a camera at this at some point." It won't be HDRI but it can get you "on set".

Anyway... I'm rambling as I tend to do... like Greggl said. 95% of the time some derivative 3point lighting is all you really need, even in matching footage, so don't sweat the IBL unless you really need it.

The real 'problem' with IBL is, it really only works well for one static object, it doesn't move well with your character. If you take a light probe on one side of the room, and your character walks around, the probe won't be at all accurate. And if you're using it as a sun source, you might as well use a directional light and save yourself minutes to hours on your render time. So by all means, use the resources you have available to you, use that fancy HDRI probe you have for super accurate reflections and as a reference for a more permanent light setup. Just don't expect it to be a magic bullet, a good conventional lighting rig will work better, more consistantly, be more controllable, and render faster.

I've also found IBL super useful for instances where I do have static lone objects. If you have that cg truck parked in the background that isn't going to be driving and nothing is going to interact with it you can not only use IBL, you can probably bake the lighting from the IBL onto it, and never have to re-render it again. The bake can be sent off to the render farm, and you waste no time trying to do a lighting match on it.

Also, never forget that you don't have to get a perfect sync in your 3d app. Just try to get as close as you can, it's the compositor's job to sell it. That last 1% is pretty damn near impossible inside of your renderer but will only take about 15 minutes in a compositing application. The cg community needs a line similar to film's "Shoot for the edit": "Render for the composite".

my half penny on the subject.

[im.thatoneguy]

After doing a bit more research... I just realized my mental ray render nodes memory wasn't as good as it used to be. [Insert foot into mouth here ->]

IBL and EnvSky are actually quite seperate properties.

IBL: Image Based Lighting is for using an image (preferably an HDRI image) to light an object.

EnvSky: Is a synthetic sky/cloud texture generator. I supppppossee you could use an EnvSky shader to drive an IBL sphere, but to limit it to the context of the question at hand, they're radically different, beyond the fact that they both use spherical gizmos.

an EnvSky will not light your scene, it will only generate a texture to (as I sudgested to do with an IBL sphere) use as a point of reference to create a light of your own.


If you want a little documentation on each here are a couple of tutorials to walk you through the two approaches.
Good EnvSky tutorial here: http://www.persistentvisions.com/Tutorials_Main/Env_Sky.pdf
An IBL discussion with a step by step Maya process:
http://www.3dbuzz.com/vbforum/showthread.php?t=129067

Now if you'll excuse me, I'm going to go hide under a rock for a few weeks in shame.

[Sony FX1 User]

use a fluids effect in maya like clouds it is much better

[im.thatoneguy]

Dear lord, and probably completely unwarranted.

Photos are your friend.

Unless you're moving the camera at supersonic speeds or changing thousands of feet in altitude, there is no reason to bring volumetrics, let alone fluid sims.

[surf]

Thanks im.thatoneguy!
I have just realizted the same things a few weeks ago! I should have more time to try out cool(er) things.