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View Full Version : VRay Light Cache Super Bright

MartinDay
07-06-2009, 12:48 AM
Hello,


I'm refreshing myself with VRay...
I've done a simple interior scene with two windows, VRay Sun and Sky (default settings and the Sun switched off) and two portal lights. The Sky is dropped in VRay Environment slot (multiplier 1)

I have used VRay camera and adjusted the exposure settings to get desired brightness of the light without any GI.
Color Mapping settings are left on their defaults.

I have also added some artificial lighting inside. I used lumen values taken from real life bulbs.
The exposure is adjusted so the incoming daylight and inside lights look both natural and correct. (the daylight is a little dark at this stage since there is no bounce light yet)

The problem starts when I switch on GI. :lightbulb
Light Cache produces suuuuper bright results. It seems the reason is in the VRay Sky that brings in extremaly bright samples. I need to turn the Envirnment multiplier down to around 0.25 to get normally looking results.
On the other hand Irradiance map gives natural results at multiplier 1.
Photon Map (default settings) looks a bit too bright but way not as bright as Light Cache.

Is it normal or am I doing something wrong? :shrug:

Thanks
thev
07-06-2009, 08:04 AM
What are your materials?

Best regards,
Vlado
MartinDay
07-06-2009, 10:48 AM
What are your materials?

Best regards,
Vlado


Ohhh, sorry. I could have mentioned that.
It all has Mtl Override - white matt VRay Material.
thev
07-06-2009, 11:07 AM
Probably this is the issue; if you have a perfectly white material, it reflects (diffusely) all light that falls on it, and light does not decay with each successive bounce, leading to a very bright result.

A solution would be to use darker and more physically plausible materials (a typical white paint coating really reflects about 60% of the light falling on it), or if you must use a perfectly white material for some reason, you can reduce the secondary GI multiplier (this will make the GI solution inaccurate though).

Best regards,
Vlado
MartinDay
07-16-2009, 12:07 PM
Probably this is the issue; if you have a perfectly white material, it reflects (diffusely) all light that falls on it, and light does not decay with each successive bounce, leading to a very bright result.

A solution would be to use darker and more physically plausible materials (a typical white paint coating really reflects about 60% of the light falling on it), or if you must use a perfectly white material for some reason, you can reduce the secondary GI multiplier (this will make the GI solution inaccurate though).

Best regards,
Vlado


Thanks Vlado, but I dont understand why is Irradiance Map so much different than Light Cache :shrug:
KingSRS
07-19-2009, 11:04 PM
hey guys im just strated learning v-ray but does some one know any tutorials cant work without learning it :P
noouch
07-20-2009, 10:31 AM
Thanks Vlado, but I dont understand why is Irradiance Map so much different than Light Cache :shrug:
AFAIK the light cache doesn't have a bounce limit, whereas Irradiance map is limited by whatever is set for secondary bounces (usually brute force). Not sure if this is correct though.
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