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View Full Version : MR:Unit-Scale of scene and FG Min/Max radius?

ghostlake114
11-26-2005, 06:24 PM
I have view the mental ray tranining CD of Alias..in this CD, I got an info that Max radius should be 1/10 of scene unit... So, the instructor use measure tool to canculate the scale of scene like this
http://i35.photobucket.com/albums/d152/ghostlake114/unitfg.jpg
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so, the Max radius mean 2
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And in digi tutor CD, they tell that the Min radius should be 1/10 of max radius
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So, this case Min radius will be 0.2.
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From this, I got some question :wip: :banghead: :banghead:
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The unit we do to canculate here is what: millimeter, centimet, metre????
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I have tried and find some relation between Min/Max radius with FG color bleeding also the artiface... but seem all the key live in Scale of scene..that must be in certain unit
Undseth
11-26-2005, 08:03 PM
The radius is in maya units, which is set to centimeter by default.

A default poly-cube is 1x1x1 units in dimension.

I don't think the "working units" like "centimeter" is anything other than a simple scale multiplier.

Setting the maya units to other than centimeter seems to make for some annoying camera-clip-plane behaviour.

If you want more accuracy with the maya units (more decimal numbers to type in the channel box), you can right click the channelbox, and choose:
"settings" --> "choose precision"
ghostlake114
11-27-2005, 12:42 AM
So, the rule above for FG Min/Max radius is for centimetre ?
Undseth
11-27-2005, 01:54 AM
No, I would not explain it as such, because I dont think it matters whether the "working units" is set to meters or centimeters. I think this FG radius setting basicly works with maya units, whether it is set to centimeters or meters as "working unit" in the preferences-settings.

"I have tried and find some relation between Min/Max radius with FG color bleeding also the artiface... but seem all the key live in Scale of scene..that must be in certain unit"

Im not sure what you mean by this.

I dont know how to specifically control any colorbleed with FGradius if that was what you meant, other than perhaps using more FGrays & lower FGraudis' to perhaps smooth things out or get better FG lighting/shadowing, at expence of rendertime.

Hmm, I have asked about scene scale in a mr forum, but did not get many replies, about whether it matters to model stuff in 1/1 scale. Like 100 units (default centimeter) corresponding to 1 meter in reality. One mentioned that some kind of shaders could perhaps depend on a specific type of "working unit" in its settings. This question was not about FGradius though but mr in general.

Btw, I do not work with CG as a living and dont work too much with maya as a hobby either, so I check the posts at cgtalk every day :) and hope to catch onto stuff as they appear.
LehaS
11-28-2005, 07:08 AM
Dont change default units...Just work with centimeters and treat them whatever you like (meters,mm,kilograms and etc.)...In my expierience "cm" worked correct and predictable with FG...
ghostlake114
11-28-2005, 11:41 AM
So, the type of UNIT is not important... They all working unit and If we will treat them all the same way... just record the length and do not care about their unit....
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Seem it is obvious now... I have known why from alias, gnomon to digi-tutor do not say anything about which unit should use but only say: So, It is 10 unit length so 1 Max radius :bounce: :bounce: :wip: :wip:
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