Going in circles with office lighting?

[CliveG]

G'day All,

 

I'm going in circles trying to achieve a realistic office ceiling like the attached pic.

 

 

I've tried using VrayIES & / or Plane lights, Light Material and GI multipliers etc. but always seem to suffer from one or more of the following - dark ceiling, excessive colour bleed from the GI off the carpet, unrealistic or flat light levels and most frustratingly poor light effect on the actual light fitting itself.

 

 

I would always want to start from as realistic basis as possible, using actual IES lighting definitions and realistic finishes and light bounces, but just seem to end up having to apply sticking plaster fixes to lighten the ceiling, reduce the GI colour bleed and attempt to get the correct representation of the light fitting itself - Whereas in the picture the chrome of the reflector is most apparent on the fittings closest to the camera and then become more white / light further away from the camera - yet with the VrayIES it's the opposite burning unevenly close to the camera and seeming to behave like some sort of point light, while providing good illumination on the carpet / walls it only lights a small section of the light fitting itself - requiring another sticking plaster to fix that. (Does working in mm mean that I have to somehow scale IES or be aware if they're meant for an 24"x24" light fitting rather than a 600mmx600mm?)

 

 

Does anyone have a tried and trusted step by step formula to achieve a realistic office ceiling / lighting without week long render times? Some good advice would be really appreciated!!

 

 

Thanks all

 

Completely confused Newbie

[Bruce Hart]

Hey there,

I see nobody has bothered to reply, so I will try to help a bit. I would change your member name too. We were all complete newbies at one point. A bit of practice and you'll be on track.

 

There have been numerous posts about whether or not to use real world light values. Personally I don't get too hung up on physically correct values all the time, and go more on what looks aesthetically correct. There were some interesting posts just the other day on going for an "eye exposure" look verses a real-world camera exposure look.

 

A few points (forgive me if you know this already):

 

the light burning can be controlled with colour mapping

http://www.spot3d.com/vray/help/150SP1/examples_colormapping.htm

 

With Reinhard mapping a value of 0.5 is half Linear mapping and half exponential.

 

Colour bleeding and the amount of light bouncing off your carpet can be controlled with Override materials (in the GI slot).

http://www.spot3d.com/vray/help/150SP1/examples_vray_overridemtl.htm#ex3

 

Some IES light shapes can throw some light upwards when pointing down. You can use the exclude option to light being cast on fittings.

 

Are you using "sky portal" lights in the windows? This will cause the renderer to sample more rays from the window direction/environment.

 

I don't know if you are using a small light source for every light fitting in the scene. Larger light planes can be used for a number of fittings. You may wish to try "store with irradiance map" for the light shadows where shadow accuracy is not critical. Shadows are stored in the GI solution, and can result in faster render times. Your IM settings may need to be a little higher tho.

 

Adaptive Subdivision AA can be a lot faster than DMC AA if you have large smooth tonal areas (due to undersampling it does). The drawback is it may not render fine tile lines properly. (You could use the object outline switch, and play with the colour threshold setting to fix).

 

In general I would suggest having a look at the tutorials on 3DATs for lighting guidelines:

http://www.3dats.com/free/

 

Hope this helps a little

[CliveG]

Thanks Bruce,

 

Yep I've got some of those fixes in hand - I guess it was just that vray seems so easy and intuitive in most other lighting situations.

 

Attached is my test render- most of what you suggest has been used, apart from storing the light shadows with the irradiance map - which I'll have to experiment with as I've no idea of this.

 

I think the way forward is to use an accurate IES just on the few lights closest the camera or those that may wash a wall - the rest just use a big plane light for.

 

Any suggestions for a good resource for IES (other than the ubiquitous erco site) as none of mine seem to provide suitable up as well as down!

 

Thanks again

 

CG