SImple Radiosity Scene Setup

[MegaPixel]

http://www.hobson-eds.com/Rad_Light_Test.jpg

 

http://www.hobson-eds.com/Rad_Light_Settings.jpg

 

The above links show my Settings and Results for my first "Simple" Interior Radiosity attempt. The scene is a Box with flipped Normals and there are 4 Can lights in the Cieling. Inside the Cans are Photometric Point Lights. The Wall is just a simple standard material with a Radiosity Override Material applied to it so I could adjust between 30% and 70% Reflectance value for Paint.

 

I do not feel comfortable about what I have produced and would like to know much much more about the do's and don'ts for Interioir Radiosity Setup. I'll just list a few of my Issues and Questions and hopefully someone can give me some tips and answers:

 

1) There doesn't seem to be enough Light Bouncing. Which Rad. setting controls this, is it Regather Illum.?

 

2) My Spotlight Attenuation seems too harsh. Which settings allow me to soften the hotspot transitions?

 

3) I can't get my Can Light's to look like they are On by Self Illuminating. I applied a Rad. Override Mat. with the proper Luminance Scale but it didn't seem to work.

 

4) Do I have to use Radiosity Override Materials on all Materials in a Radiosity Scene or is it mainly used for Reflectance or Luminance adjusting?

 

I'll stop there for now. I was hoping this could be a simple Radiosity Exercise for beginners and perhaps even a Tutorial could be created from it eventually. Anyhow I'd like to know how others setup there Rad. Scenes differently or any comments and suggestions on what I've done here so far. Thanks guys - Mega

[Jennifer]

Hi,

 

You do need to make sure that the scale of the scene is correct. If it is too large then the light dissipates before it can bouce around.

 

Your radiosity "mesh size" is 4.0, but what units is that? And how does that relate to the size of the box? Are subdivision faces being generated in your box at all?

 

Using real-world units and object sizes is the first thing, then go from there.

 

You should not have to use the Override material in most instances. Start simple, without the Override Mtl, ad add it if you need it.

 

Since the walls look flat, it looks like you have Ambient lighting and no radiosity effect at all. Perhaps load one of the sample files and modify it from there?

 

Have fun!

[Uirsu]

hei MegaPixel

 

first, what program are you using (Max or Viz) ?

sec, set the exposure control to logarithimic

to use attenuation, set it manually or download some web files (http://www.erco.com)

and finally, add some objects to the scene

[ZepSOFD]

MegaP,

 

1) Start with simple white diffuse material with V (HSV Color) set to 204 that should give you roughly 80% relfectance to your mat.. Dump all overrides for now.

 

2) Check your ceiling height it looks to low for the intensity of your hotspots on the floor. As Jennifer suggested double check the scene scale and make sure you are using the correct IES lighting standard (American, International). Those spotlights at 1300cd should give you a soft hotspot at about 10'/3meters off the floor, when used with the exposure control values you have listed.

 

3) To get the self-illumination to show up at a level you deem appropriate you need to increase the physical scale value to 10,000 or above(most likely above).

 

4) As far as the override mat. there really are only a handfull of occasions when you need to apply it. Even when you are trying to control color bleed it's really not required in most cases.

 

Try this and see what you get.

 

tom

[MegaPixel]

Thanks Jennifer,

 

My System Units are in Inches and the Box is a 10ft by 12ft Room by 9ft High (About a small Bedroom. I assumed when I entered 4 for the meshing size, it meant 4 inches. I always try to model to scale if I can. As for th flat looking walls, I have no idea why they look so flat. Maybe something is screwy with my Material. Again, there are only 4 Photometric Point Lights in the Scene.

 

Uirsu,

 

I am using MAX 5.1 Radiosity (I was pretty sure this was the correct forum for this post ). As far as setting the Attenuation Manually, I sure would like too but I couldn't find where to do it with the Light I selected. It wasn't as obvious as standard lights were.

 

Zep,

 

So basically, I should just forget about the Overide Mat. except on occasions where I want a Self Illuminating Surface? Based on what all of you are telling me, I should scrap this scene and start all over again. I know I've taken all of your suggestions into consideration and for the life of me, I can't figure out why it looks so bad. I'll start this same scene all over from scratch tommorow following your suggestions to the "T" and we'll see what happens then.

 

I wasn't planning on doing anything more with this scene other then setting up a generic Rad. Light Scene. There is still so much I don't understand like when is it appropriate to use the Radiosity Overide Material or picking the appropriate light for a particular scene and even setting the light up properly. I swear I will write a tutorial on this once I figure out how to acheive good results. It seems like getting the right recipe for Radiosity is untangable.

 

Thanks for all your help guys - Mega

 

[ July 28, 2003, 06:40 PM: Message edited by: MegaPixel ]

[ZepSOFD]

MegaP,

 

Also try it without the volume light setup, just a straight up spotlight. Maybe that is holding back some of the light energy.

 

 

25'x25'x10' room

Mat. white diffuse V 204

4 spotlights just below the ceiling

Halogen

8500 cd

Hotspot 45d

Falloff 60d

Adv. Ray. Shadow

Exposure Control

Log.

Brightness 70

 

tom

[MegaPixel]

Zep,

 

I noticed the same hard light edges in your render sample. Is it not possible for a Spot Light to have a somewhat softer edge around the outer circle on the floor?

 

And on a side question, do the default Light types like "Halogen, Fluorecent, Halide, etc..." start you with realistic energy values or do you have to look up every light type and it's appropriate "real-world" value online somewhere like Erco?

 

I'm just loaded with Newbish questions and don't worry, I'll have more. Thanks again Zep - Mega

[ZepSOFD]

MP,

 

For a spotlight distribution type you can increase the falloff angle just like a standard light. In the image below I increased the falloff from 60d(first image) to 120d, huge diff..

 

"Halogen, Fluorecent, Halide, etc..."

This is for light color/temperature, but in some cases can have the appearance that the light is producing more/less intensity then it is set for. Right Wrong or Indifferent you'll use this setting to change the tone of your scene for those people who let their minds fool them into believing that white has an V of 255 under all lighting conditions. White takes on whatever tint that the light produces.

 

Most of the time you are going to use Web distribution just because it is easier to paint light with. You can pick .ies and other lighting standard formats from various fixture manufacturers on the net. You may need to do a little research to find out the model number of the fixture you want to use, then get the matching file, but this is fairly easy and saves time during lighting setup.

 

tom

[Jet]

Hi Mega,

As far as the units go, make sure that if you are using ft and inches, you have it set that way in the units setup, and also set the lights to American. I have found that this works better when I check that out. I believe that if you use the decimal of a foot measurement and adjust your lighting values, it will still hold true

 

Jet