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royter
08-22-2007, 12:23 AM
i heard once that this is better to work in cm especially if you are rendering out FG or GI.
now i am not sure in rendering terms what that means.

i am working presently on a scene with meters as units. I noticed that the change from cm to meters affects values such as the spread of the AO shader but not the bump value.

what exactly in MR is affected by the scene unit: color gain, bump, ao spread, light falloff??

phix314
08-22-2007, 09:52 AM
As far as I know it's distance based calculations, which is why AO and FG would change, as well as Global Illumination computations and the like, which is why it's usually recommended to model in cm and scale up to get more "realistic" measurements.

mindsample
08-22-2007, 11:08 AM
AO wont change unless you are using max_distance with a setting other than 0.

same goes for FG.

It is more relevant that having falloffs on lights etc. these will require adjustments after re-scaling the scene.


Generally: Dont do it and stay with centimetres!

royter
08-22-2007, 05:55 PM
Generally: Dont do it and stay with centimetres!

i model and render envirnemnts and sticking with .cm is really frustrating....

mindsample
08-23-2007, 09:18 AM
Why? Because things are "too big" ?

Well I suppose if you go for metres at the start of your work there is no problem, I was just refering to changing the units within an already established scene.

But personally (and this might just be my preference) I always stick with cm. The units are arbitrary anyways, if you have dimensions in metres just make them centimetres. Its just about relation not about actual dimension.

bwheels02
08-23-2007, 04:28 PM
I would suggest not using cm as for the scene settings if using Mental Ray (or any renderer really). Reason being is if you have very intense lights calculated in such a small (cm) space light will oddly leak through the seams in your geometry. This is less likely to happen in larger scenes. There are many issues with creating too small an enviornment I have found. It never hurts to use larger settings anyways, just adjust clipping planes and Photonic attributes accordingly. :)

royter
08-23-2007, 07:09 PM
I would suggest not using cm as for the scene settings if using Mental Ray (or any renderer really). Reason being is if you have very intense lights calculated in such a small (cm) space light will oddly leak through the seams in your geometry. This is less likely to happen in larger scenes. There are many issues with creating too small an enviornment I have found. It never hurts to use larger settings anyways, just adjust clipping planes and Photonic attributes accordingly. :)

and FG radius of course and the ao distance.

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