Final Gathering: Use in realistic scenes?

[gmask]

The color of over objects does effect the surrounding environment. Try placing a white piece of paper next to a brightly colored object and see if you can't see the color being picked up on the paper.

In most cases this effect may be exagerrated in renders as it is really a subtle effect most of the time.

To create the effect in a non FG render you just place a color light pointing at the surface receing the radiance.

[wurp]

the intensity of the colorbleeding has little to do with FG really, it depends on the shader. In XSI there is a node called RayType which can be used to control both the intensity and color of the colorbleeding. You could for example have a red object that emits blue colorbleeding on other objects....

Also, FG is not the next fad after GI when it comes to trendy rendering as you say... its been in mental ray for ages and is simply a method to compute ambient lighting, just as GI.

GI and FG are designed to be used together but they also work good when used alone. I believe most renderers uses similar methods for GI....

[Jozvex]

Hi,

I've got two photos here showing colour bleeding for you, and then an image I put together in Maya with a similar effect to show how it can be useful:

Photo 1: This is a photo of the real life Cornell Box, used for comparison when testing GI renderers etc

http://www.graphics.cornell.edu/online/box/measured.jpg

Photo 2: I've just sat three household items onto a piece of paper and the effects of colour bleeding are quite clear.

http://www.jozvex.com/temp/ColourBleeding.jpg

CG Image:

http://www.jozvex.com/temp/FinalGathering.jpg

[klingspor]

Thanks for the replies everyone, especially Jozvex for your example images. I now understand where Final Gathering applies.


Then on the other hand, isn't it trivial to setup a scene looking like Jozvex's third image using simple point or perhaps area-lights? FG can save you parts of the lighting-setup, yet the rendering-time is horrendous in comparison, no?

Just let me put it this way: Is FG generally used in the industry, where render-times have a much higher priority than for the single-frame rendering hobbyist? I hear that they're slowly starting to implement GI solutions and have been using (baked) Ambient Occlusion for quite some time now... what about FG?

[wurp]

Final Gathering can be slow if you use the wrong settings, learning how to tweak them takes some skill and experience, its not a click-and-render solution actually. FG and GI is still in most cases unusable in animations as the result change from frame to frame, one option is to go for very high accuracy settings, another is to blur out the FG effect a lot by using very high min/max settings. Occlusion passes is most defeneatly a good alternative, they wont flicker in animation, even if they are noisy and also it renders much more accurate than FG as far as detail goes. Occlusion wont do any colorbleeding but honestly, I can live without that, its better to try to fake it in most cases.

I would not consider any GI renderer ready to be used in animation yet, not for all situations anyway. There are solutions like final renders hyperGI but it has limitations and will only work in some scenes.

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