photon question

[Virgil Johnson]

If I set the Average GI Photons per Light (Render Setup dialogue box)

at 10...

 

1. and I have only the Daylight mr sun in the scene.

I then set the mr Indirect Illumination (modify panel) for the mr sun at 10, then the sun is now shooting 100 photons?

 

If that is so then is there a difference if I just set the Average at 100 and the sun Indirect at 1?

 

2. If I have another photometric light (and the Average is at 10) and set its Indirect Illum. at 10 and the sun at 10 do I have 200 photons total?

 

What is the difference if I just set the Average at 200 and set the two lights in Indirect Illum. at 1? Will their emitting photon output be equal?

 

I take it if I set the Average at 10 and the sun at 15 and the other photometric light at 5 I will have total of 200 photons but the lights emit proportionally?

 

3. My understanding the physical sky provides light but not in the form of photons?

 

4. And lastly, how does the energy setting affect the photons?

 

Virgil

[Justin Hunt]

The best way to understand and find out how many photons are being shot, open and read the message window. It will tell you exactly how many phtons each light is shooting.

 

If you want to specify exact photon numbers set the light photons to Manual.

 

Correct that the sky doesn't shoot photons, you can trick it to do so by using portal lights.

 

Energy settings basically control the intensity of the photon. A basic explination as its alot more involved to go into in one post.

 

For a really good explination of Photons I highly suggest Mental Bout Max tutorials. Also take a look at Master Zaps blog, he has a really detailed explination http://mentalraytips.blogspot.com/2007_03_01_archive.html

 

and one on physical scale http://mentalraytips.blogspot.com/2008_02_01_archive.html

 

jhv

Edited May 13, 2009 by Justin Hunt

[Virgil Johnson]

The best way to understand and find out how many photons are being shot, open and read the message window. It will tell you exactly how many phtons each light is shooting.

 

If you want to specify exact photon numbers set the light photons to Manual.

 

Correct that the sky doesn't shoot photons, you can trick it to do so by using portal lights.

 

Energy settings basically control the intensity of the photon. A basic explination as its alot more involved to go into in one post.

 

For a really good explination of Photons I highly suggest Mental Bout Max tutorials. Also take a look at Master Zaps blog, he has a really detailed explination http://mentalraytips.blogspot.com/2007_03_01_archive.html

 

and one on physical scale http://mentalraytips.blogspot.com/2008_02_01_archive.html

 

jhv

 

The answer to my questions is in the first sentence. Open the message window.

What a concept. duh

 

(I had reviewed the MBM stuff and could not seem to find what I was looking for.

I had also read what Zap had to say.)

 

But the thread about rendering times with your energy screen shots brings up the question about "intensity.

 

It looks to me that the higher energy is making the photons more or less scatter out more into the scene but only in local sense.

 

Am I right in thinking that there is simply more light appearing in places farther from the "focal point" of the photons there by adding more light in a local area but not over the whole scene?

 

It is almost as if the energy setting is extending out a kind of "decay" distance.

 

Virgil

[Justin Hunt]

Simplest way i found of understanding it, it to separate concept of the lights intensity and the photon intensity.

 

Think of the lights intensity of the brightness of the direct light, and the energy as the intensity of the indirect light. Simplified I know, but will do for this explanation.

 

So if the energy is high it stands to reason that it will travel further before decaying. It is still following the inverse square rule. Therefore will light up areas further away.

 

The way I calculated what to set the photon energy in the thread you mentioned was to Divide 80 000 by the light intensity, in that case 800 = 100

 

Why 80000, back in the day of using Logarithmic exposure control we used 80 000 as the physical scale which relates to the intensity of the sun.

 

HTH

 

JHV

[Virgil Johnson]

Yes Justin.

 

It fits with my take on it also.

 

One more bit of the puzzle goes into place.

 

Thanks for the help in making it clear.

 

(btw I like the MBM tip on using curves to find the physical scale)

 

 

Virgil

[Justin Hunt]

I think I missed that one, what is the tip?

 

jhv

[Virgil Johnson]

Justin

 

select the daylight

get the curve editor via the quad menu

 

scroll down to the sun

check the intensity from the curve editor

 

to be honest I got this from MBM

I would never have figured it out my own.

 

Virgil