Originally posted by studioDIM
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GI "life" multiplier or similar
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u got a pretty nice button up on the navigation bar "search"...just give it a go!
what ur asking here as been adressed tons of times...so a little up-to-date reading is a must.
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GI bounces, multiplier and gamma - that's all you're looking for.
The number of bounces which is only really relevant to secondary bounces set to qmc or photon mapping. It will affect how many times the light can bounce before cutting off - i'd say most people would recommend using light cache for secondary gi though where you just get infinite bounces.
Gi Multiplier will affect how much energy the light loses each bounce and will determine how quickly it fades off - Vray has the max of this set to 1 - there is no current way to make GI bounce more light than it has received in keeping with the realistic approach of vray.
Gamma - it'll affect how bright the midtones of your image are and is probably the biggest part of lwf. As Lele mentioned there's tonnes of stuff out there for it.
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"Gi Multiplier will affect how much energy the light loses each bounce and will determine how quickly it fades off" - I didn't realise that. Thanks
This is from Vray Help.
"...this determines the effect of secondary diffuse bounces on the scene illumination. Values close to 1.0 may tend to wash out the scene, while values around 0.0 may produce a dark image. Note that the default value of 1.0 produces physically accurate results. While other values are possible, they are not physically plausible."
This is the reason I was confused that it is overall sec bounce light multiplier.
Apparently I'm totally wrong again
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People used to use the gi multipliers to reduce the effect of colour bleeding which in the case of bright colours tended to be a bit too saturated and unnatural, this tends to be taken care of by gamma instead.
Yep - vray tends to split the GI into primary and secondary for speed / quality reasons. when light first bounces off a surface, it can make some quite sharp and detailed light patterns - if you shine a light on a box in max you'll see quite a sharp bit of light where the light is bouncing off the corners of the box - you need a really high quality GI method to properly render this such as qmc or irradiance mapping.
The bounces after the first one tend to be a lot softer since the light has been scattered around a lot more and as a result there isn't much fine detail. For these bounces you probably want to get a soft smooth lighting solution and as a result you can use a lot more cheating to speed everything up with something like light cache or photon mapping - light cache is a lot more efficient than photon mapping and you're getting infinite bounces effectively.
That's the main reason why the two are separated - for the best combination of speed and quality and also why you end up with two different multipliers. As vlado mentioned leaving both at 1.0 is the most physically accurate but sometimes it's handy to have a quick way of cheating.
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