Getting the brightness value of lights

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On 17/04/2003 at 06:25, xxxxxxxx wrote:

User Information:
Cinema 4D Version:   8.100 
Platform:    Mac  ;  
Language(s) :   C.O.F.F.E.E  ;

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How can I get the brightness value of a specific light for a given point in space, using COFFEE? I mean, imagine I have world coordinates (X,Y,Z). How can I get the brightness value of Light1 (for instance) for that point in space (taking into account the light type, the decay, the color, etc)? And for all lights in the scene?
Can I also get the RGB values? Will they be clamped?
Thank you very much in advance.

Rui Batista

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On 17/04/2003 at 06:28, xxxxxxxx wrote:

This is only possible from within a shader in C.O.F.F.E.E. Then you can use the various Illuminate() functions. I'm pretty sure that the C.O.F.F.E.E. values are clamped, but I haven't checked.

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On 17/04/2003 at 06:38, xxxxxxxx wrote:

Only within a shader?!? Not possible anywhere else? :-(

Rui Batista

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On 17/04/2003 at 10:48, xxxxxxxx wrote:

No, since the render engine has to be active. You could of course fake it by calculating fall-off etc. manually, but I wouldn't recommend it since those things aren't 100% documented. Besides, I'm not sure you can get all light properties from C.O.F.F.E.E. in R8 yet.

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On 17/04/2003 at 10:59, xxxxxxxx wrote:

This is a big drawback :-(
We should have that info available. Mmmmm I guess I will have to do it by hand. Any place I could get some info about it? For instance, how do I know if the point is inside the cone of light?

Rui Batista

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On 09/02/2006 at 17:45, xxxxxxxx wrote:

hey rui!
after 3 year maybe this topic will answer your question!!!
http://www.cgtalk.com/showthread.php?s=&threadid=50291
it's an Xpresso node called "lightmeter". this is how it works
1. Create a NULL object as a child of the light you want to check. This NULL object defines the location in your scene where you want to sample the light.
2. Right click on the light, and add an expresso expression.
3. In the expresso editor, use the FILE menu to load the light_meter.xma xgroup.
4. Right click on this xgroup, and select "unpack" so that you can see the two "results" boxes.
5. The two results boxes will show you the color and intensity of the light at the location defined by the NULL. The values range from 0 (0%) to 1 (100%).

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On 09/02/2006 at 17:54, xxxxxxxx wrote:

The page from which I could load the .xma file was not found. Do you have the .xma file?

Rui Batista

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On 10/02/2006 at 14:59, xxxxxxxx wrote:

hi Rui!
i get in touch yesterday, with the guy ( color=#800080bcbarnes <SCRIPT type=text/javascript> vbmenu_register("postmenu_", true); _<_Script_>_ )who posted the thread,
and here is what he replied:
"Wow - I haven't thought about that one in a long time. Unfortunately, I've rummaged through all my old scene files, and don't have it anymore. Sorry.
If I remember correctly, there is an XPresso node that will give you the brightness of a light, and I just hooked the position up to a null object so I could move it around.
Hope that helps.
brian."
i hope this will really help you.
i tried to find it myself but i didn't. i'm too fresh for that stuff!
actually, i am trying to set an xpresso for "photometrics" kind of lights, using Terrabrush for converting Eulumdata (data distribution) files. i think lightmeter will be a great help for my testings.
i wonder if the brightness of lights can be limited. i mean if the brightness of the lights (if they are on) @ daylight, is greater than the brightness of the sun oblect, then it can be "slightly" ignored by Gi solytion. i think this is what is happening in real life, as light fixtures don't add much in daylight, but make all the difference @ night.
if you are interested i could send you my wip in progress.
george.

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On 26/10/2006 at 09:29, xxxxxxxx wrote:

hey rui,
while trying to explore xpresso capabilities,
i finally managed to set-up the light-meter.
if you are interested let me know, so i can send the file with the xpresso expression.
cheers,
george drakakis

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On 27/10/2006 at 10:43, xxxxxxxx wrote:

Yes, I'm quite interested :)
Could you send it to [email protected]?
Thank you very much :)

Rui Batista

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On 27/10/2006 at 13:30, xxxxxxxx wrote:

hey rui,
check your e-mail.
hope it helps you.
cheers,
george