Cycles works in metric, hardcoded for 1 unit = 1 meter, so you should stick to that if you’re working with Cycles like most users. Cycles doesn’t respect Blender’s unit conversion system, so the light calculations will be off if you use a different scale.
If you use another renderer, you can always change the clipping values, but they should be sensible by default, no?
Maybe they could adjust with the units you choose to work with (meters, millimeters etc.). I’ve been having some clipping issues lately as well.
There is already a setting for that. In Scene->Units. It’s just that cycles doesn’t respect it.
oh, I know. as I said, it is defintely problematic, but it helps to root out some issues:
Gravity for the walk mode used to be hard coded, now it respects scene gravity setting
The scene gravity setting used to be capped at 100 bu/sec^2, now it is 1000 (381 inches/sec^2 is standard gravity)
The viewport AO used to not scale well with distances over 2, now it smoothly scales all the way up.
I do have to crank my lights way up in cycles, and DOF is always tricky too, but I make it work.
It is often distinctly suboptimal, but sometimes, you gotta do what you gotta do to get stuff done.
This is not really true, Cycles is not hardcoded to any unit. Like Blender and most other renderers, the unit system is a display and editing feature. If you change the distance unit, other units should also be considered to be changing accordingly.
For example for lights, by default the power is 1 W = 1 kg m^2 / s^3. If you change that m to mm, the watt will change to microwatt. We don’t display units for power in Blender though, so this isn’t communicated.
I see. I’m sure you’ve considered this, but why aren’t the units being adjusted to compensate on export to Cycles? I don’t think anybody really expects light power units to change because they adjusted the grid.
Thanks for the explanation in any case.
Typically renderers and interop file formats do not modify the stored values, but copy them as is. Modifications cause precision loss, break shaders, break animation curves and drivers, break image textures, etc. Leaving the unit system as a display and editing feature keeps the result predictable.
Even if this could be done reliably, what should Cycles do? If it would compensate for both distance and power units, it would be a no-op. If it would compensate for power units only, how is it helpful for lights to become much brighter/darker relative to the rest of the scene? It’s much better to try to handle this at the editing and display level, changing the default power when a light is added, showing the appropriate units in the UI, etc.
At the risk of someone shouting “speak for yourself!” at me - what your average user expects is that a scene at 1BU = 1m should render the same as the same scene at 1BU = 1cm, with the same values set for lights, as long as the scale is actually set in the units tab.
Sure, but that is why support for display of power units is needed. It’s not up to the renderer to do that conversion.
Not up to the renderer, no, but the Cycles ‘addon’ that handles export from Blender should. Just displaying the right units would be a good step forward, but ultimately you’d just want Watts to remain Watts, and Candelas to remain Candelas, and Nits to remain Nits, regardless of scene scale.
But your meters don’t stay meters already when you change the unit scale of a scene, why should watts be treated differently?
Meters always remain meters, it’s just the BUs that change their meaning.
And watts remain watts, it’s just the power-BUs that change their meaning.
Yes, because Blender doesn’t actually display a unit for the light power, it’s technically correct as it is now.
It’s just that nobody expects the light power units to be affected in any way by BU scale - we expect it to be expressed in terms of some kind of physical value based on SI units.
This is because the connection (through that formula) between these two numbers - the BU scale and the light power unit - is so extremely obscure to… well… anyone but you, because you’ve written it. 
Not obscure, just a bit inconsistent (Sun VS Lamp - 1st confusing element).
Also, only a few “artists” honestly care for physical properties & technicalities using SI standard units (2nd & 3rd confusing element - no simple terms and inconsistency again - what is Candela?) 
So for a common player, it becomes really hard & stressful to find inner peace trying to unite mind in combined knowledge - why majority of shinny happy loving people rather just turn & run away.
From Blender Cycles manual: Emission
Lamp strength for point, spot and area lamps is specified in Watts. This means you typically need higher values than Blender Internal, as you could not use a 1W lamp to light a room; you need something stronger like a 100W lamp.
Sun lamps are specified in Watts/m2, which require much smaller values like 1 W/m2. This can be confusing, but specifying strength in Watts would not have been convenient; the real sun for example has strength 384.6×1024W. Emission shaders on meshes are also in Watts/m2.
What is Radiance? (wiki)
“Speak for yourself!!!” #shakes fist in furious anger 
Seriously,… i was often importing stuff from fbx files (with wrong Unit-scale) and i got really sick and tired of increasing the far clipping value each and every time and searching the horizon for the imported models.
It’s far too low. And the near clipping is also too big, i often see black clipping errors on the models.
Thank the makers for customizeable startup files.
Like you said, I don’t actually care that it’s an SI unit or not, just that it remains consistent when the scale of the BU changes, thus making identical scenes at different scales render the same.
As I understand it, that quote from the manual is only true as long as 1BU = 1m.
a blender’s axiom, beyond shadow of a doubt 
Sorry guys,
I’ve a “problem” with viewport.
i’m not sure if it’s an option but I can’t find anything related.
My problem is that, everytime I switch to the edit mode (both solid view mode and wireframe one) I see also all the edges, so for example, with a cube I see all the triangles with edges that connect opposite vertices.
Is this behaviour correct?
Is there a way to hide that edges?
I’ve checked the object viewport display options and it seems that anyone of that changes this.
thank you
screenshot?