Document Properties: Units settings
Manages the units settings for the current model.
Controls the units used in the model. When you change from one units system to another, Rhino asks if you want to have the geometry automatically scaled to match the unit change.
Tolerance in units used when creating new geometry that cannot be absolutely accurate. For example, trimming surfaces, doing offsets and Boolean operations usually create approximate geometry.
Sets the relative tolerance used in some commands. If, in those commands, the relative tolerance is smaller than the absolute tolerance setting, the relative tolerance is used instead.
Sets the angle tolerance in some commands use. When creating or modifying geometry, Rhino will use this value to create or modify its approximate geometry so its angle is less than or equal to the tolerance. When evaluating geometry, Rhino considers two pieces of geometry as meeting some criteria such as tangency if the angle between them is less than or equal to the tolerance value.
The unit name.
Enters a scale in units per meter.
Sets the distance display for the status bar and distance and length commands.
Sets the display to decimal (1.25).
Sets the display to fractional (1-1/4).
Sets the display to feet and inches (1′-3″).
Sets the number of decimal places for the distance display.
It is best to select a tolerance when you start modeling and stick with it.
Importing a model in a format that supports units and tolerances will not adjust Rhino’s units or tolerances. A dialog box will warn you if the units do not match.
The following three items are a good guide to choosing tolerances.
Rhino can work in any unit system and with any tolerance. The default unit system is millimeters, and the default tolerance is 0.01 millimeters. You can change the default unit system or tolerance by setting up a template. If you frequently need to work in more than one unit system or with more than one tolerance, set multiple templates.
In general, Rhino works best if you choose a unit system whose absolute tolerance is around 0.01 to 0.001, the “size” of a small feature (like a tiny fillet or small curve offset distance) is >= 10 x tolerance, and the “size” of the model is <= 100000.
Using an absolute tolerance that is smaller than 0.0001 will noticeably slow some intersection and fitting processes.
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