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tkpolak
08-11-2012, 01:37 PM
Hello. This might be even interesting for some of you.

Realistic light have quadratic decay rate, we all know that.
So let's say one wants to lit a candle aka simulate a candle flame. So what does he do?
Create area light in spherical shape, maches the shape of the flame and sets its decay to quadratic. Then set its shader to mia_photometric and set its parameters as it fits the scene in correct scale. The colour is connected to mib_blackbody with a candle flame temprerature.

And here it is.. a professionaly set node that should reflect the flame of the candle. That is what I've learned through days of online research. Now take a look at the image please (btw I know modelling is not perfect, I am only interested in lighting this):

http://img687.imageshack.us/img687/7052/10108193.jpg

Please dont mind the candle to the right, there is only a weak point light there. The left one has the light I described.

So what do? If the decay rate is set to quadractic I always end up in a situation where the closest objects are completely overburned, yet if I decrease the values the objects I am interested in enlighting are too dark. I could change the decay rate but then it won't be physically correct therefore not realistic.



I would appreciate any help and I believe this is child's problem for some of you.

I am using Maya 2012. Oh and by I did not enable photon emission in the light itself, Maya is so bugged that it crashes instantly after enabling it and there no solution on the web..

leif3d
08-11-2012, 03:20 PM
By the look of your blacks, it doesn't look like you're working linearly, therefore your lights will not behave like the real world, they will be blown out at close proximity with geometry.

LBcover
08-11-2012, 03:57 PM
Make sure you are working linearly as stated before.

You need to tone the intensity of your lighting down, thats why it's blowing out. A candle is no where near that bright.

As for making your character brighter, I'd add a key light on him matching the candles color. Esentially, you create your realistic candle light as just a starting point, and then enhance it with supporting lights for the desired look you are going for.

Panupat
08-11-2012, 04:13 PM
Apart from using linear work flow, when we shoot on actual set, most of the time we can't use candle light alone. It's not bright enough to give good exposure on actors. If we turn up the f-stop too high, the candle will be over exposed. So we'll have a spot light shining in from the left too that is kind of matching the direction of the candle.

leif3d
08-11-2012, 05:43 PM
Apart from using linear work flow, when we shoot on actual set, most of the time we can't use candle light alone. It's not bright enough to give good exposure on actors. If we turn up the f-stop too high, the candle will be over exposed. So we'll have a spot light shining in from the left too that is kind of matching the direction of the candle.

Good points.
Besides Barry Lyndon I can't think of another movie that was actually shot in candle light alone. Most of the time you want to get creative with the lighting, no need to be perfectly accurate, but convincing and emotional.

tkpolak
08-11-2012, 05:48 PM
Yup I didn't mention that I am not working lineary yet. I just thought I'd set some basic lighting first and then skip to linear mode. Linear renders do take longer.. don't they? I compared it once but tbh can't recall xd

You need to tone the intensity of your lighting down, thats why it's blowing out. A candle is no where near that bright.

Really... :P And the light is placed on the flame..

As for making your character brighter, I'd add a key light on him matching the candles color. Esentially, you create your realistic candle light as just a starting point, and then enhance it with supporting lights for the desired look you are going for.

Apart from using linear work flow, when we shoot on actual set, most of the time we can't use candle light alone. It's not bright enough to give good exposure on actors. If we turn up the f-stop too high, the candle will be over exposed. So we'll have a spot light shining in from the left too that is kind of matching the direction of the candle.

Both super useful thank you. I just started to play with the scene and I need tons of adjustments yet. I'll show you what I've got when I think it is good enough. The only problem I can think of now is this spotlight. There should be two, one on character one on a desk.. they need to match the brightness.

So you say I should go linear right away?

leif3d
08-11-2012, 07:01 PM
Yup I didn't mention that I am not working lineary yet. I just thought I'd set some basic lighting first and then skip to linear mode. Linear renders do take longer.. don't they? I compared it once but tbh can't recall xd
No, no they don't.
Linearity deals with the gamma of the image (color profile), so no extra computation is needed. Maybe for linearizing the incoming textures their might be an insignificant penalty, but nothing else.

mister3d
08-12-2012, 01:31 AM
No, no they don't.
Linearity deals with the gamma of the image (color profile), so no extra computation is needed. Maybe for linearizing the incoming textures their might be an insignificant penalty, but nothing else.
They may take longer if sampler understands it's working in linear more, so it takes longer to get rid of noise, which otherwise it would ignore due to gamma falloff. So when you make your gamma-corrected preview, it's not just preview, but the renderer actually supposes it's as bright when sampling the noise. Vray can do it.

Panupat
08-12-2012, 04:22 AM
Linear workflow may take a little while to understand. So the sooner you get to it the better.

tkpolak
08-12-2012, 04:10 PM
So... I finished basic lighting and moved to linear mode with this (https://vimeo.com/27393252) method.

Apparently camera lenses make issues when you want to work with render layers. If you don't want to waste your time watching it ill explain it quickly -> changing display mode in maya instead of using camera lens to view the image. It forces working in openEXR though.

http://img341.imageshack.us/img341/1993/unoduo.jpg

I lost all of the dramatic look I was after because of linear :C Any suggestions how can I quickly get some of it back? Shall I re-adjust all the lights again by hand?

And do you seriously think it looks better in linear? I know it needs some post work but.. I am not convinced.

Panupat
08-12-2012, 04:27 PM
When working linearly, your final render may have sRGB gamma applied which will brighten up your image (depends on your settings of course) So you may have to reduce your light's intensity. Maybe increase it's color saturation too to get that rich red-orange tone back.

If the clothes are still washed out after your darken the light, you might have to make sure you apply gamme correction to your texture too.

Take note that your character's hand is no longer burned out which is a good thing. You can still get that orange glow on your hand back with sub surface scattering which should look a ton better than the burned out lighting.

tkpolak
08-12-2012, 04:45 PM
I liked the light on his hand.. qq. All of my textures&colours are gamma corrected now. As in mentioned tutorial I set this:

http://img14.imageshack.us/img14/6813/31313131.jpg

..instead of camera lens, so I can't play with crushing blacks and all the cool stuff anymore.

Panupat
08-13-2012, 03:42 AM
Definitely go with what you like :) It'd still be good exercise trying to get linear work flow to look good.

mister3d
08-13-2012, 03:18 PM
Crash blacks only in post. It's always easier than having more information, and is what you shouldn't do in the renderer engine. It's normal images may seem a bit blank from the renderer. Actually it's correct, and what you see in photographs has applied contrast curve to them, as people got used to it from kodak times. Photographs also have such a blank look initially (internally). Forget about non-linear work, it's incorrect at all.

LucentDreams
08-15-2012, 01:42 AM
You'll see the same with any serious photographer or Cinematographer. They should with the flattest color profiles possible. It makes for an initially flatter more boring image, but with a hell of a lot more information for you to work with prior to adding the saturation and contrast.

Remember adding contrast always reduces information in your image, so if you start with high contrast there isn't much to work with.

http://philipbloom.net/2011/09/18/pictureprofiles/

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