View Full Version : help with indoor lighting

05 May 2004, 01:23 PM
Hi there buddies. :buttrock:
Well, Im working in a new model. An indoor scene illuminated through the light that comes from an open window.
OK, the idea is that my scene looks (in lighting) something like this one: Dinin Area Image (

I was trying with MR, but I cannot achieve this look...
Ok, this is my setup:
If you see my simple model (below, attached), you'll see a room corner and a window on the left, where light comes from.
I use a MR area spot (far) to simulate the sunlight, with a multiplier of 1.5 and a SKYlight (1.5 multiplier too). Ok, the problem is that it's not illuminated!!!! Im using 10.000.000 energy globally, and in the first render a multiplier of 5 (50.000.000 photons). I don't know how to get more light in the room, because if I add more photons, color BLEEEEEDS! (get it?) and I don't really know if I get more bounces adding more energy...
Maybe I need to add some inner lights (to fill the scene) but it would like not real...
I don't know how to get that...
Any ideas????

The images are below. Thank you buddies.

(first image: 50.000.000 photons energy. Sorry about the sampling and FinalGathering sampling, but it's just a test)

05 May 2004, 01:25 PM
(and the second image: this one has only 10.000.000 photons, and ican't see any light in the room... :cry: )

05 May 2004, 03:46 PM
Try to lower the decay.

05 May 2004, 07:45 PM
do u think that 2.0 decay (default) is right?
what does 2.0 mean? what kinda measure is it?

05 May 2004, 12:22 AM
the decay satting lets you tweak at what rate indirect illumination "fades out", or you could say, how far it travels.

2.0 is the decay rate of real world light (inverse square), but may not give the look your after.

For you there are two options:

1. Set your decay lower

2. use Logarithmic Exposure Control and experiment with the Physical Scale setting.

If you want to know more about indoor illumination and how to get your wanted effect you should check out this tread I started.

click here:
realistic lighting in mental ray (

05 May 2004, 02:58 PM
I've begun to understand how decay works in real life. Actually I need more reading about this matter...

I will post some renders ASAP with different setups to keep the thread alive... he he :thumbsup:

Many thanks to you Asomma, cause that thread is great!

:beer: Wait 4 new renders buddies.

05 May 2004, 03:34 PM
Ok... this is really cool...
I lowered the value of the decay from 2 to 1.5 and look at this...!!!! god da** it! it's completely overlit!!!!!'s pretty difficult to understand how decay works... mmm...

Im reading the Asomma's thread...

All the same, tale a look
(image attached)

05 May 2004, 04:55 PM
The you can just up the decay a bit. Maybe 1.8 will do it for you?

read the thread, and start using logarithmic exposure control right away - then youll get the hang of it!

05 May 2004, 10:02 PM
mabey increase the decay (less bounce)

I read this from asomma's topic.
is it true that decay value is closely related to bouncing?
...I was using another renderers as Brazil, for example, and I got used to the "bounce" value, but there is no "bounce" setting here in MR... :D

05 May 2004, 10:08 PM
Yes fabrizzio,

you may say that decay is related to bouncing.

Decay means, I would say, how much energy the photons looses as they bounces in your scene

Have you tested the logarithmic exposure control?

05 May 2004, 11:03 PM
Actually Asomma, I never used exposure control before...
I have no idea.
What is it for?

05 May 2004, 11:32 PM
another test:

1 million energy
1.5 decay
mr spot area 1.5 multiplier
Skylight 1.5 multiplier
GI photons 10.000

take a look.
Do I need to slower the decay?
or what to get more lighting?

05 May 2004, 09:01 AM
Just try Logarithmic Exposure Control.
I just explained how in the realistic lightning thread where you asked about it.

05 May 2004, 02:17 PM
I've been reading about EXPOSURE control in Max Help and it's not such the big thing, but Im testing right now...
Im working only with PHYSICAL SCALE, as I read in the help (for first attempts). I hope Im in the right way. I'll post some results soon.

05 May 2004, 02:23 PM
I've been reading about EXPOSURE control in Max Help and it's not such the big thing, but Im testing right now...

Im talking about the help... not the program... Ok? (the big thing)

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