CGTalk > General Techniques > Lighting and Shaders
To minimize the ads you see on this page create a CGTalk account and log in HERE
Thread Closed share thread « Previous Thread | Next Thread »  
 
Thread Tools Search this Thread Display Modes
Old 01-12-2006, 10:00 AM   #1
Macko-San
Wannabe
Marcus
Wannabe
Karlstad, Sweden
 
Join Date: Dec 2005
Posts: 60
Need for decay when using GI?

Im attempting a photorealistic rendering of a room, and Im using inverse square falloff on the lights since I have understod that is the way real light behaves.

But controlling the light intensity across the scene seem to be a real problem. Some areas apear to bright (overexposed) and some to dark. Ive been trying to correct this by experimenting with the multiplier and decay start values for the lights. But this is a pain since testrenders take so much time. Overall my sceen apear to bright and lacking contrast. Just plain and dull.

So my question is if there is any need to use any decay on the lights when Im using GI? GI alone might suply enough variation in the shading?

The room has three flouresent lights in the celling, a small light in the window, and three small lights on a shellf in the room illuminating the shellf. Im thinking about not using any falloff on the flouresent tubes, thereby making the main illumination easier to control, and use decay on the small lights to provide variation in the illumination in those local areas.

What do you guys think?
 
Old 01-12-2006, 03:05 PM   #2
FrizzleFry0
Lord of the Potroasts
 
FrizzleFry0's Avatar
portfolio
Jared Edwards
Course Director
Full Sail University
Orlando, USA
 
Join Date: Dec 2004
Posts: 440
Send a message via AIM to FrizzleFry0
I don't know if you'd necessarily want to take off the decay from an interior light source. Although GI does provide a gradient look for secondary bounces, I think if you had no decay on your light source it would blow out too many areas. Are you rendering out your lights in seperate layers? You may want to consider this not only for the sake of controlling your render times, but it will allow you to adjust intensities quickly in post work.
__________________
Jared Edwards
Course Director
Visual Development
 
Old 01-12-2006, 09:51 PM   #3
Ian Jones
Design & Technology
 
Ian Jones's Avatar
Ian Jones
Multimedia Technologist
Brisbane, Australia
 
Join Date: Aug 2002
Posts: 2,219
Don't forget that controlling the number of bounces has an good deal to do with controlling the spread of illumination.
 
Old 01-13-2006, 07:54 AM   #4
Macko-San
Wannabe
Marcus
Wannabe
Karlstad, Sweden
 
Join Date: Dec 2005
Posts: 60
Jared

Thanks. Im pretty new to this whole thing, how does rendering lights in layers work?

Ian

Ok, thanks. Ill look into that.


Do you guys know if theres a right way to set the lights? The flouresent lights have a multiplier of 8, inverse square decay and a start value about 1 meter. Does that sound good? Are there any guidelines to follow when setting up these kinds of scenes or do I have to rely on my own judgement?
 
Old 01-13-2006, 10:57 AM   #5
playmesumch00ns
Lord of the posts
 
playmesumch00ns's Avatar
render monkey
pretty picture maker
United Kingdom
 
Join Date: Jul 2002
Posts: 3,420
Are you doing a gamma lookup on the image when you view it? This can drastically change the apparent falloff of lights.

You should be viewing the image with a gamma of 2.2

This will mean you'll have to gamma-convert your textures, there's a couple of tutorials linked in threads here about working in linear colour space. Try searching for them.
__________________

You can have your characters photoreal, fast or cheap. Pick two.
 
Old 01-13-2006, 10:58 AM   #6
CGTalk Moderation
Lord of the posts
CGTalk Forum Leader
 
Join Date: Sep 2003
Posts: 1,066,481
Thread automatically closed

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.
__________________
CGTalk Policy/Legalities
Note that as CGTalk Members, you agree to the terms and conditions of using this website.
 
Thread Closed share thread


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
CGSociety
Society of Digital Artists
www.cgsociety.org

Powered by vBulletin
Copyright 2000 - 2006,
Jelsoft Enterprises Ltd.
Minimize Ads
Forum Jump
Miscellaneous

All times are GMT. The time now is 05:59 AM.


Powered by vBulletin
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.