View Full Version : Lighting a city (office buildings, neon etc)
04 April 2006, 05:24 AM
I did a quick search and there were a few minor topics, but no real particular answers for ways to light a city. What I am think of here are mainly the office buildings/skyscrapers. Given that you are are going to have a LOT of buildings in an average city shot, does anyone have ideas on how to get a quick/effective lighting system going. Self-illumed/glow materials? Render out mat id's and do it in post with glow filters? Light maps?
Thanks for any info. For the record I am using max7/8.
04 April 2006, 05:44 AM
If you're using textures then you can just paint the windows and give them a self-illuminating material. If you're not using textures then yes, rendering out alphas of the windows and colouring those in post sounds like a good idea. You might also want to consider mixing that with a Z-Depth map so you can make the light darker or tinted the further it gets, for a moodier image. Double cool!
In a realistic image the windows wouldn't visibly illuminate the buildings around them anyway, unless they're really close. Only the ground when they are at ground level.
But I'm sure there are other ways to do this.
05 May 2006, 09:10 AM
I've searched CG too but did'nt find anything on how illuminating "small" glo cityscape.
I tried with light sources but the rendering time then takes hundreds of years !
Found good useful refernces photos on this 3d
if any matter painter.. good soul want to help plz ;)
I've modelled tyrrel Balde runner tower but I'm stick before rendering :(
05 May 2006, 12:20 PM
you don't really say whether this is an aerial view or street level, but you could try the following.
Create a free direct light on the floor pointing up at the sky. Make the light cone big enough to fill a city block.
Make it rectangular and ambient only.
Attenuate the light so when you render, it falls off the further it goes up the buildings.
This will be a bit flat (and obviously won't cast shadows, but will be quick to render)
What you can then do is put a bitmap in the projector slot of the light with variation in colour, brightness etc.
This could give you a quickly rendering starting point for streetlights.
05 May 2006, 01:43 PM
One other thing, you can then add a volume light environment to the fdirect, and that will give you a coloured haze over the city, which might be nice if you're going for a Blade Runner look.
So basically, I would go for some kind of self-illumination for the buildings (obviously the lit windows, but uplighters as well), then have a wash of this fdirect light for the streetlighting.
You may want to add some actual lights for specific street lighting in the foreground that can cast shadows but the fdirect will help light the rest of the city at the expense of shadows.
Bear in mind you can have negative lights as well, so if you find that the scene is bleaching out you can have attenuated omni lights set to ambient and a -1 multiplier which will darken areas.
Here is a quicky test - it's overdone, but you can see the idea.
05 May 2006, 01:50 PM
Really Thanks for the suggestion that what I was searching to explain.
Probably some small light have to do in post prod.
This week I hope to find the time to do the rendering for my finished modelli Tyrrel Tower.
05 May 2006, 02:18 PM
Here's an animation that shows it off a bit better - the buildings were knocked together very quickly but it gives an idea.
05 May 2006, 06:56 AM
nice effects - i am working on a file at the moment but from the city street level and animation pulls back through streets (approx 4-6 stories off ground)
what would you recommend for lighting a scene like this?
05 May 2006, 07:39 AM
well I would probably use that method for the distant streets, and just place omni lights for your street lights where it's close to the camera and switch to the ambient lights further back.
The calculation of the shadows for lots of omnis can take a while, but hopefully you wouldn't need too many.
I wouldn't really bother having lights emitting from building windows, unless something is passing in front of them (like a bird, or steam from a vent) but again you can get away with lighting only what you need to.
If there are floodlights attached to the building you may want to have them as lights, but they could probably be baked in, or maybe have some low-level lights to simulate it bouncing back to the street.
The best thing though, is to just study a similar shot in a movie or TV show and look at what is happening in the scene.
05 May 2006, 08:05 AM
This week almost finished modelling tyrell tower (I was not satisfied with modelling so I remodell top part of the tower) the animation posted is simply AMAZING :buttrock:
Also a hint about the texture you used could be very helpful :love:
I will post the model finished as soon as possible
05 May 2006, 08:38 AM
Is the image of ambient-streets.jpg using one fdirect light or a few set to diff colours?
also wondering what your project map looks like?
05 May 2006, 06:41 PM
it's two lights, but the colours are created by a bitmap in the projector slot.
At the moment the bitmap is just a messy splash of colours with pools of light, and grid lines which are quite soft.
What I intend to do is to render the street model from the top down, with geometry where the lights should be and use that as reference, or place proper omni lights in there and render that to use as a bitmap to project back up.
Here's a slightly newer version - I'm just experimenting with how much geometry I can get away with. One of the buildings is just a texture from a photo of the HSBC building in London, shot in daytime, and I created a self-illum map from that.
The ground buildings use one texture for the diff map, and another for the illum map, with tiles used to break up repetition on the lights. I need to create a bunch of different ones though. It's all at the R&D stage at the moment.
05 May 2006, 06:52 PM
For the light projection texture, you want something along these lines (but flat, not tilted)
For the buildings, you can either source some real night-time shots of office windows, but then you'll need a tripod to get a clear image. Or you can adapt daytime shots (which is what I did on one of the buildings)
It's also good to make the windows reflective, so that they are reflecting the lights of other buildings, otherwise it looks too flat, I also put a subtle noise bump on the glass so the reflections ripple slightly.
05 May 2006, 07:35 PM
Here's a 4 second clip
I've got to finish off a job in the next few days, so I won't be doing any more on this until that is finished. Hope it's inspired people :)
05 May 2006, 12:33 PM
really thanks steve for every suggestion, I'm working too in these days but my modelling at night almost finished (my first job is chemistry :)) now I was just tryying to find textures for the background since my Enlgish not perfect I would like to say
Properly taught, a student can learn more in a few hours than he would find out in ten years of untutored trial and error. -Emanuel Lasker :wise:
05 May 2006, 12:54 PM
You're welcome Giorgio,
It's been good for me to work out a technique that doesn't take an age to render.
The animation I posted was taking about 6mins a frame at 1920x1080 on a Dual Xeon 3GHz. That was using Brazil, but it could be done in the scanline using a raytrace material for the glass or Mental Ray and the result should be pretty much the same I guess.
05 May 2006, 12:54 PM
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