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royterr
01-30-2006, 05:34 PM
Hello, i am trying to simulate an indoor lighting with mental ray.

i have a well formed poly model ( a normal house), but when emiting photons from a cone or a point light something weird happens:

-the cone is placed in behind a wall.
-there is some light leaking at the bottom of the wall as if light passes threw the poly geometry.
-no FG, the same problem occure with dmap and ray trace shadows (raising the Gi accuracy doesn't do anything)
http://www.aedii.qc.ca/v2/fichiers/uploads/section_4/l_prob.jpg

DeletedPenguin
01-30-2006, 06:55 PM
are you using two separate objects? if so, you might have a small space between the two...

royterr
01-30-2006, 07:02 PM
no it's the same object, formed by poly boolean operation.

suggestions?

CupOWonton
01-30-2006, 07:11 PM
From my experience, photons essentialy ignore the fact there's an edge, and keep streching out in 3d space. So, either use more photons per lightsource using the global or local light settings, and constrain their size to 1" or .25" *depends realy, how thin your smallest noticible object is, or turn on Final Gather.

royterr
01-30-2006, 08:31 PM
well u r right, it's a photon leak (threw a geometry problem).

i found a solution (but there is still a small amount of photons leaking threw the wall), by increasing the photon number to a 1000000 (very expensive....)
decreasing the gi radius to 10
and using final gather

This is a common artifact, even Matt Hartle experience it in his GI Gnomon trainig dvd, and didn't fix it.

nothing seems to stop those photons.....

i hope that somebody could help...

CupOWonton
01-30-2006, 09:19 PM
What happens when you take off the size constraint and leave FG on?

jeremybirn
01-30-2006, 09:32 PM
Just build a thicker wall.

-jeremy

royterr
01-30-2006, 10:57 PM
What happens when you take off the size constraint and leave FG on?
using only fg would darken the image. My goal is lighting with photons



Just build a thicker wall.
I have tried to do that but u will have a 6 foot thick wall!!! who wants that.
i tried extruding faces, even adding geometry to stop the photons....
nothing seems to work. It's so anoying, i don't know if i am asking to much from mental ray.....

CupOWonton
01-31-2006, 05:51 AM
"would" ? Meaning you didnt try?

Just take off the constraint on the photons so they automaticly spread, and leave FG on.

And I've never had FG "darken" an image, you can cast light with FG and an illuminated plane. alone.

Also, never build with booleans, period.

jeremybirn
01-31-2006, 02:03 PM
FG brightens (never darkens) the image and smooths out the photon map.

Walls don't need to be 6 feet thick if your photon radius is less than that. You do need to be careful how you build your geometry, though. If you are sloppy in how you build things, the difference will be visible. Often a photon radius of 0 is a good starting point, because that chooses the photon size automatically based on the number of photons.

Be sure you have your problems isolated and don't have any light leaks due to shadows. Test with just shadows and no GI to make sure.

-jeremy

royterr
01-31-2006, 03:02 PM
"would" ? Meaning you didnt try?

Just take off the constraint on the photons so they automaticly spread, and leave FG on.

And I've never had FG "darken" an image, you can cast light with FG and an illuminated plane. alone.

Also, never build with booleans, period


i am not new to GI and Fg, i know that FG smoothes the images, but my goal isn't to create a plane with a surface shader to light the scene via FG. Yes i tried using FG alone, only a small portion of the room is illuminated.....i am only trying to illuminate with photons, a room with one door.
What do u mean by taking of the constrains?
and why never build with booleans?

royterr
01-31-2006, 03:29 PM
FG brightens (never darkens) the image and smooths out the photon map.

Walls don't need to be 6 feet thick if your photon radius is less than that. You do need to be careful how you build your geometry, though. If you are sloppy in how you build things, the difference will be visible. Often a photon radius of 0 is a good starting point, because that chooses the photon size automatically based on the number of photons.

Be sure you have your problems isolated and don't have any light leaks due to shadows. Test with just shadows and no GI to make sure.



i have tried it all, my object is simple and well formed.
i always try to isolate my problem and thats why i start with gi only.

thank alot guys. I am going to pass you the simple scene:
http://www.aedii.qc.ca/v2/fichiers/uploads/section_4/light_leak_1.mb
hoping you will find out what's the prroblem.

mewantelfears
01-31-2006, 10:08 PM
try adding more geometry around your edge, that sometimes works

royterr
02-01-2006, 12:56 AM
one more thing ....yes FG does smooth the image but it could darken it.


Only GI:
http://www.aedii.qc.ca/v2/fichiers/uploads/section_4/GI.jpg


GI + FG :
http://www.aedii.qc.ca/v2/fichiers/uploads/section_4/FG_GI.jpg

LOOK_AT_ME
02-03-2006, 05:29 PM
dude the file is no more please reload .........

NeptuneImaging
03-04-2006, 11:21 PM
Hey Royterr,

I too am having the same issues with MR doing that...even with no Gi turned on light leaks through my geometry...I don't know how to get around it....it is really starting to aggravate me too, and all of my photons are setting at 1M photons in Max....with no radius...maybe I should try and fix it...

NeptuneImaging
03-05-2006, 12:30 AM
Hey, Jeremy, your radius trick really worked!! Thanks a bunch...

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