2.3: Physical Units
On installing Karamba3D one can specify the family of physical units to be used for input and results. The default option is metric (e.g. meters, centimeters, degree Celsius, Newtons, …) but Karamba3D can also deal with Imperial units (e.g. feet, inch, degree Fahrenheit, kiloponds, …).
The set of units to be used can be changed any time via the Grasshopper/Karamba3D menu or by editing the “karamba.ini” file.
Depending on the family of units Karamba3D interprets geometric input either as meters or feet by default. The kind of physical units that components expect to receive shows up in the tool-tip which appears when the mouse pointer hovers over an input-plug.
Karamba3D comes with databases for predefined cross sections and materials. The properties there are given in SI units. The same applies to physical constants (e.g. “gravity”) defined in the “karamba.ini”-file.
Throughout the rest of this manual SI units will be used exclusively in order to ensure good readability. When specific differences exist between using Karamba3D with Imperial Units and SI units, this will be mentioned in the text.
Non-default Physical Units
In case of very small or very large models the default physical units may become cumbersome to work with. The "karamba.ini"-file contains three parameter settings to change the basic physical units which Karamba3D uses for internal calculation and geometry input from Rhino: "UnitLength", "UnitForce" and "UnitMass" (see fig. 2.3.1). Possible values for the unit-identifiers are listed in the karamba.ini-file as comments. All input- and output values will be converted to and fro these units. The units can be arbitrarily mixed - make sure however not to use imperial- and SI-units at the same time.
The basic physical units serve for internal book-keeping and geometry input from Rhino. In order to change the physical units for input and output use the "CustomUnits"-parameter in "karamba.ini" (see fig. 2.3.2). This parameter expects a list of comma-separated terms of the form "'original unit'>'custom unit'". If handed over an empty list the default units apply.
The new units apply to all Karamba3D components. You are free to mix SI and Imperial Units if you feel like it.
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