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View Full Version : Real-looking overexposure in a bright room?


twosheds
12-04-2010, 10:42 PM
Hiya. :)

I'm wondering how to get that overexposed look in a room, such as when your camera is facing a window with very bright sunlight outside. You know, the way the area around the window seems to almost glow pure white, but doesn't necessarily blow out everything in the room, since the effect dies off.
I guess this is a result of the light being too bright for the shutter speed and blowing it out at the main light source?
If I were a photographer maybe I'd have the proper terminology, but I'm just a modeler and texture artist of game assets and a part-time arch viz wannabee, so I don't know how to describe it. ;)

I'm wondering how to do this with mental ray, in either Maya or Softimage, although I suspect the technique would be more or less the same with mr in either.

pokoy
12-06-2010, 02:15 PM
What you're looking for is the glare or bloom effect. There's indeed a glare shader in mray, though you'd have to search for how it's used in maya/xsi.

soulburn3d
12-06-2010, 02:22 PM
I'd do it in post using a piece of compositing software. It's just faster to dial in the exact settings you'll want.

- Neil

mister3d
12-06-2010, 08:33 PM
I'd do it in post using a piece of compositing software. It's just faster to dial in the exact settings you'll want.

- Neil
There may be antialiasing issues if exposure is taken too high in post, and noise may appear. Maybe if you set up a very high-quality sampling it won't.

kanooshka
12-06-2010, 09:49 PM
If you're going to do it in post I'd recommend rendering in at least 16 bit but 32 bit is preferable. That way there's more information to work with.

jipe
12-07-2010, 02:07 AM
Just out of curiosity, what does everyone use in post? I see recommendations like Sapphire from GenArts, but last I looked that's over $1500. I've never used anything but the default glows in After Effects so I suppose I don't know what I'm missing.

soulburn3d
12-07-2010, 03:01 AM
That's certainly something to be aware of, if you push things too far in post, you can break your elements. So yes, stuff like rendering to a float format is certainly very helpful.

jipe, we use Shake for our work. But there's also Digital Fusion, Nuke, a whole ton of software. Most of it is pretty expensive though, if you're just doing stills, you can pretty much do the same thing in photoshop, which I also frequently use for post on my personal projects.

- Neil

MisterS
12-14-2010, 10:02 AM
If you do it in post - i.e turn blow highlights down to zero in the exposure control in your 3D software then how do you control the antialiasing?

In Max I found even saving out an EXR with no clipped highlights made my AA settings take no effect in areas that would have been high contrast/blown out.

playmesumch00ns
12-14-2010, 12:14 PM
If you do it in post - i.e turn blow highlights down to zero in the exposure control in your 3D software then how do you control the antialiasing?

In Max I found even saving out an EXR with no clipped highlights made my AA settings take no effect in areas that would have been high contrast/blown out.

That's just down to how your renderer handles antialiasing (in the worst case with many pixel filters you'll get negative values there too). You shouldn't try and turn things down that much for exactly that reason - unless you've got ridiculously high antialiasing settings you'll lose information in super-high-contrast pixels.

MisterS
12-14-2010, 01:46 PM
Is that just a pitfall of outputting linear/hdr images that you can't avoid without stupidly high AA settings? I'm using Max btw.

soulburn3d
12-14-2010, 05:39 PM
Each renderer handles antialiasing a bit differently, so there's no one solution that fits all. I'd do a few tests and see how far you can push an image value-wise in post at various antialiasing settings of your renderer of choice.

- Neil

jeb
12-15-2010, 09:48 PM
In mental ray its true that high highlight value on exposure control cause really high float point contrast values and anti alias cant handle that. i always just adjust contrasts in post apps like after effects, composite or combustion. as said above if you render in float you get a much better range of color and tone values to push and pull. also i recommend you get the image looking more neutral and not too contrasted out of the renderer, that way even anti alias works faster.

my 2 cents.

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