View Full Version : Radiocity in City

09-20-2003, 05:43 PM
I' making a city and i have another question about 3d city. What radiocity mode willbe the best for city [Monte Carlo, Backdrop Only, Interpolated]. ANy suggestion, ideas?

I know maybe my question is lame but usually i'm making 3d scenes and object for real time and now i want try to make something realistic :-)

09-20-2003, 08:18 PM
It depends on the scene. If there are no special lights within the city(daylight), then set up a sky using SkyTracer or a bitmap...then use Backdrop. It will render fast, and if you use a high resolution bitmap, it will look really good too.

On the other hand if you have a lot of light and would like to use them in the radiosity calculation, then use Interperolated(hope I spelled that correctly). Or if you don't mind the long render times, use Monte Carlo.

In the end it all really depends on how long you want to have to wait. If it's a full-blown city, then you should set it up to render over night or something. Hope that helps.

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09-21-2003, 05:58 AM
Exactly this will be a daylight with bitmap as sky. Ok one more question what will be the best "Rays per Evaluation" or it's doesn't matter?

Thanks for you help.

09-21-2003, 03:17 PM
The Rays Per Evaluation setting is almost what you could call the "quality" or "resolution" of the radiosity. Ok, maybe not resolution, but quality would be the visual word for it. Resolution could be used for the math terms. Anyway, it sets up how many rays are used to determine the radiosity. Basically, the higher, the better; but once again, the longer the render times.

If you set it real low, you'll notice it will look dirty, or even ugly. Depending on the scene, this could be wanted, but 99% of the time, it is unwanted; especially with your scene. I don't really know how to explain it but to tell you to render and compare different settings. I usually use 4x12, and 7x21. But I also have a 1.3 ghz AMD and don't usually do animations with radiosity(I just recently bought a new computer with a 2.4 ghz Pentium 4 with HT, haven't installed Lightwave yet to it though so don't know if there's faster rendering). Even with those settings, it can take awhile.

If you are just rendering a nice big image of your city, then pump up the Rays Per Evaluation and render overnight. Before make sure to test the quality with different settings at low resolutions, then render at full resolution. If your doing an animation, there are a couple of things you could do to speed up rendering...

Bake radiosity on the objects, or

Use Interpolated and find comfortable settings, especially with the Tolerance value, or

You can use the "fake" radiosity method which is explained in several websites and tutorials around the net. It uses a bunch of lights set up in a certain way. There are also many plugins that automate this process.

Hope this helps.

[email protected]

09-21-2003, 04:00 PM
If you're rendering lots of high poly buildings it'd probably take too long to render using radiosity. My advice would be to render two seperate scenes. One that uses radiosity for lighting near foreground buildings, and another scene that uses standard lighting techniques for background buildings. Then composite them together later.

Alternatively, light each building seperately using radiosity and bake it into the model. Then bring all your baked buildings together into the final scene for rendering. You'd miss the inter-building indirect illumination, but you could fake that with standard lights for anything that's close to the camera.

09-21-2003, 05:26 PM
Thx guys for this fast tutorial. I will try to bake radiocity into the objects. My project is almost done[about 70%] When i finish it i will put this to Vbulletin. Tonight i will make preview with radiocity. One more time thx for help.

09-23-2003, 07:43 AM

This might help.