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API
3.3
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API
3.3
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This class serves as a serializable TendonForceLengthCurve for use in muscle models. More...
Inheritance diagram for OpenSim::TendonForceLengthCurve:Public Member Functions | |
| TendonForceLengthCurve () | |
| The default constructor creates a tendon-force-length curve using the default property values and assigns a default name. More... | |
| TendonForceLengthCurve (double strainAtOneNormForce, double stiffnessAtOneNormForce, double normForceAtToeEnd, double curviness) | |
| Constructs a tendon-force-length curve using the provided parameters and assigns a default name. More... | |
| TendonForceLengthCurve (double strainAtOneNormForce) | |
| This constructor will create a C2-continuous tendon-force-length curve that is fit to match the average dimensionless in-vivo tendon curve reported by Maganarius et al. More... | |
| double | getStrainAtOneNormForce () const |
| double | getStiffnessAtOneNormForceInUse () const |
| double | getNormForceAtToeEndInUse () const |
| double | getCurvinessInUse () const |
| bool | isFittedCurveBeingUsed () const |
| void | setStrainAtOneNormForce (double aStrainAtOneNormForce) |
| void | setOptionalProperties (double stiffnessAtOneNormForce, double normForceAtToeEnd, double curviness) |
| double | calcValue (const SimTK::Vector &x) const override |
| Implement the generic OpenSim::Function interface. More... | |
| double | calcValue (double aNormLength) const |
| Evaluates the tendon-force-length curve at a normalized tendon length of 'aNormLength'. More... | |
| double | calcDerivative (double aNormLength, int order) const |
| Calculates the derivative of the tendon-force-length multiplier with respect to the normalized tendon length. More... | |
| double | calcIntegral (double aNormLength) const |
| Calculates the normalized area under the curve. More... | |
| SimTK::Vec2 | getCurveDomain () const |
| Returns a SimTK::Vec2 containing the lower (0th element) and upper (1st element) bounds on the domain of the curve. More... | |
| void | printMuscleCurveToCSVFile (const std::string &path) |
| Generates a .csv file with a name that matches the curve name (e.g., "bicepsfemoris_TendonForceLengthCurve.csv"). More... | |
| void | ensureCurveUpToDate () |
Property declarations | |
These are the serializable properties associated with this class. | |
| OpenSim_DECLARE_PROPERTY (strain_at_one_norm_force, double,"Tendon strain at a tension of 1 normalized force") | |
| OpenSim_DECLARE_OPTIONAL_PROPERTY (stiffness_at_one_norm_force, double,"Tendon stiffness at a tension of 1 normalized force") | |
| OpenSim_DECLARE_OPTIONAL_PROPERTY (norm_force_at_toe_end, double,"Normalized force developed at the end of the toe region") | |
| OpenSim_DECLARE_OPTIONAL_PROPERTY (curviness, double,"Tendon curve bend, from linear (0) to maximum bend (1)") | |
| Public Member Functions inherited from OpenSim::Function | |
| Function () | |
| Function (const Function &aFunction) | |
| virtual | ~Function () |
| virtual void | init (Function *aFunction) |
| Function & | operator= (const Function &aFunction) |
| virtual double | calcDerivative (const std::vector< int > &derivComponents, const SimTK::Vector &x) const |
| Calculate a partial derivative of this function at a particular point. More... | |
| virtual int | getArgumentSize () const |
| Get the number of components expected in the input vector. More... | |
| virtual int | getMaxDerivativeOrder () const |
| Get the maximum derivative order this Function object can calculate. More... | |
| Public Member Functions inherited from OpenSim::Object | |
| virtual | ~Object () |
| Virtual destructor for cleanup. More... | |
| virtual Object * | clone () const =0 |
| Create a new heap-allocated copy of the concrete object to which this Object refers. More... | |
| virtual const std::string & | getConcreteClassName () const =0 |
| Returns the class name of the concrete Object-derived class of the actual object referenced by this Object, as a string. More... | |
| virtual const VisibleObject * | getDisplayer () const |
| Methods to support making the object displayable in the GUI or Visualizer Implemented only in few objects. More... | |
| virtual VisibleObject * | updDisplayer () |
| get Non const pointer to VisibleObject More... | |
| bool | isEqualTo (const Object &aObject) const |
| Equality operator wrapper for use from languages not supporting operator overloading. More... | |
| Object & | operator= (const Object &aObject) |
| Copy assignment copies he base class fields, including the properties. More... | |
| virtual bool | operator== (const Object &aObject) const |
| Determine if two objects are equal. More... | |
| virtual bool | operator< (const Object &aObject) const |
| Provide an ordering for objects so they can be put in sorted containers. More... | |
| void | setName (const std::string &name) |
| Set the name of the Object. More... | |
| const std::string & | getName () const |
| Get the name of this Object. More... | |
| void | setDescription (const std::string &description) |
| Set description, a one-liner summary. More... | |
| const std::string & | getDescription () const |
| Get description, a one-liner summary. More... | |
| const std::string & | getAuthors () const |
| Get Authors of this Object. More... | |
| void | setAuthors (const std::string &authors) |
| Set Authors of this object, call this method in your constructor if needed. More... | |
| const std::string & | getReferences () const |
| Get references or publications to cite if using this object. More... | |
| void | setReferences (const std::string &references) |
| Set references or publications to cite if using this object. More... | |
| int | getNumProperties () const |
| Determine how many properties are stored with this Object. More... | |
| const AbstractProperty & | getPropertyByIndex (int propertyIndex) const |
| Get a const reference to a property by its index number, returned as an AbstractProperty. More... | |
| AbstractProperty & | updPropertyByIndex (int propertyIndex) |
| Get a writable reference to a property by its index number, returned as an AbstractProperty. More... | |
| bool | hasProperty (const std::string &name) const |
| Return true if this Object has a property of any type with the given name, which must not be empty. More... | |
| const AbstractProperty & | getPropertyByName (const std::string &name) const |
| Get a const reference to a property by its name, returned as an AbstractProperty. More... | |
| AbstractProperty & | updPropertyByName (const std::string &name) |
| Get a writable reference to a property by its name, returned as an AbstractProperty. More... | |
| template<class T > | |
| bool | hasProperty () const |
| Return true if this Object contains an unnamed, one-object property that contains objects of the given template type T. More... | |
| template<class T > | |
| const Property< T > & | getProperty (const PropertyIndex &index) const |
| Get property of known type Property<T> as a const reference; the property must be present and have the right type. More... | |
| template<class T > | |
| Property< T > & | updProperty (const PropertyIndex &index) |
| Get property of known type Property<T> as a writable reference; the property must be present and have the right type. More... | |
| void | setObjectIsUpToDateWithProperties () |
| When an object is initialized using the current values of its properties, it can set a flag indicating that it is up to date. More... | |
| bool | isObjectUpToDateWithProperties () const |
Returns true if no property's value has changed since the last time setObjectIsUpToDateWithProperties() was called. More... | |
| void | readObjectFromXMLNodeOrFile (SimTK::Xml::Element &objectElement, int versionNumber) |
| We're given an XML element from which we are to populate this Object. More... | |
| virtual void | updateFromXMLNode (SimTK::Xml::Element &objectElement, int versionNumber) |
| Use this method to deserialize an object from a SimTK::Xml::Element. More... | |
| virtual void | updateXMLNode (SimTK::Xml::Element &parent) |
| Serialize this object into the XML node that represents it. More... | |
| bool | getInlined () const |
| Inlined means an in-memory Object that is not associated with an XMLDocument. More... | |
| void | setInlined (bool aInlined, const std::string &aFileName="") |
| Mark this as inlined or not and optionally provide a file name to associate with the new XMLDocument for the non-inline case. More... | |
| std::string | getDocumentFileName () const |
| If there is a document associated with this object then return the file name maintained by the document. More... | |
| void | setAllPropertiesUseDefault (bool aUseDefault) |
| bool | print (const std::string &fileName) |
| Write this Object into an XML file of the given name; conventionally the suffix to use is ".osim". More... | |
| std::string | dump (bool dumpName=false) |
| dump the XML representation of this Object into an std::string and return it. More... | |
| void | clearObjectIsUpToDateWithProperties () |
| For testing or debugging purposes, manually clear the "object is up to
date with respect to properties" flag. More... | |
| virtual bool | isA (const char *type) const |
| The default implementation returns true only if the supplied string is "Object"; each Object-derived class overrides this to match its own class name. More... | |
| const std::string & | toString () const |
| Wrapper to be used on Java side to display objects in tree; this returns just the object's name. More... | |
| PropertySet & | getPropertySet () |
| OBSOLETE: Get a reference to the PropertySet maintained by the Object. More... | |
| const PropertySet & | getPropertySet () const |
Additional Inherited Members | |
| Static Public Member Functions inherited from OpenSim::Function | |
| static Function * | makeFunctionOfType (Function *aFunction, const std::string &aNewTypeName) |
| Static Public Member Functions inherited from OpenSim::Object | |
| static void | registerType (const Object &defaultObject) |
| Register an instance of a class; if the class is already registered it will be replaced. More... | |
| static void | renameType (const std::string &oldTypeName, const std::string &newTypeName) |
| Support versioning by associating the current Object type with an old name. More... | |
| static const Object * | getDefaultInstanceOfType (const std::string &concreteClassName) |
| Return a pointer to the default instance of the registered (concrete) Object whose class name is given, or NULL if the type is not registered. More... | |
| template<class T > | |
| static bool | isObjectTypeDerivedFrom (const std::string &concreteClassName) |
| Return true if the given concrete object type represents a subclass of the template object type T, and thus could be referenced with a T*. More... | |
| static Object * | newInstanceOfType (const std::string &concreteClassName) |
| Create a new instance of the concrete Object type whose class name is given as concreteClassName. More... | |
| static void | getRegisteredTypenames (Array< std::string > &typeNames) |
| Retrieve all the typenames registered so far. More... | |
| template<class T > | |
| static void | getRegisteredObjectsOfGivenType (ArrayPtrs< T > &rArray) |
| Return an array of pointers to the default instances of all registered (concrete) Object types that derive from a given Object-derived type that does not have to be concrete. More... | |
| static void | PrintPropertyInfo (std::ostream &os, const std::string &classNameDotPropertyName) |
| Dump formatted property information to a given output stream, useful for creating a "help" facility for registered objects. More... | |
| static void | PrintPropertyInfo (std::ostream &os, const std::string &className, const std::string &propertyName) |
| Same as the other signature but the class name and property name are provided as two separate strings. More... | |
| static Object * | makeObjectFromFile (const std::string &fileName) |
| Create an OpenSim object whose type is based on the tag at the root node of the XML file passed in. More... | |
| static const std::string & | getClassName () |
| Return the name of this class as a string; i.e., "Object". More... | |
| static void | setSerializeAllDefaults (bool shouldSerializeDefaults) |
| Static function to control whether all registered objects and their properties are written to the defaults section of output files rather than only those values for which the default was explicitly overwritten when read in from an input file or set programmatically. More... | |
| static bool | getSerializeAllDefaults () |
| Report the value of the "serialize all defaults" flag. More... | |
| static bool | isKindOf (const char *type) |
| Returns true if the passed-in string is "Object"; each Object-derived class defines a method of this name for its own class name. More... | |
| static void | setDebugLevel (int newLevel) |
| Set the debug level to get verbose output. More... | |
| static int | getDebugLevel () |
| Get current setting of debug level. More... | |
| static Object * | SafeCopy (const Object *aObject) |
| Use the clone() method to duplicate the given object unless the pointer is null in which case null is returned. More... | |
| static void | RegisterType (const Object &defaultObject) |
| OBSOLETE alternate name for registerType(). More... | |
| static void | RenameType (const std::string &oldName, const std::string &newName) |
| OBSOLETE alternate name for renameType(). More... | |
| Static Public Attributes inherited from OpenSim::Object | |
| static const std::string | DEFAULT_NAME |
| Name used for default objects when they are serialized. More... | |
| Protected Member Functions inherited from OpenSim::Function | |
| void | resetFunction () |
| This should be called whenever this object has been modified. More... | |
| Protected Member Functions inherited from OpenSim::Object | |
| Object () | |
| The default constructor is only for use by constructors of derived types. More... | |
| Object (const std::string &fileName, bool aUpdateFromXMLNode=true) SWIG_DECLARE_EXCEPTION | |
| Constructor from a file, to be called from other constructors that take a file as input. More... | |
| Object (const Object &source) | |
| Copy constructor is invoked automatically by derived classes with default copy constructors; otherwise it must be invoked explicitly. More... | |
| Object (SimTK::Xml::Element &aElement) | |
| Construct the base class portion of an Object from a given Xml element that describes this Object. More... | |
| template<class T > | |
| PropertyIndex | addProperty (const std::string &name, const std::string &comment, const T &value) |
| Define a new single-value property of known type T, with the given name, associated comment, and initial value. More... | |
| template<class T > | |
| PropertyIndex | addOptionalProperty (const std::string &name, const std::string &comment) |
| Add an optional property, meaning it can contain either no value or a single value. More... | |
| template<class T > | |
| PropertyIndex | addOptionalProperty (const std::string &name, const std::string &comment, const T &value) |
| Add an optional property, meaning it can contain either no value or a single value. More... | |
| template<class T > | |
| PropertyIndex | addListProperty (const std::string &name, const std::string &comment, int minSize, int maxSize) |
| Define a new list-valued property of known type T, with the given name, associated comment, minimum (==0) and maximum (>0) allowable list lengths, and a zero-length initial value. More... | |
| template<class T , template< class > class Container> | |
| PropertyIndex | addListProperty (const std::string &name, const std::string &comment, int minSize, int maxSize, const Container< T > &valueList) |
| Define a new list-valued property as above, but assigning an initial value via some templatized container class that supports size() and indexing. More... | |
| PropertyIndex | getPropertyIndex (const std::string &name) const |
| Look up a property by name and return its PropertyIndex if it is found. More... | |
| template<class T > | |
| PropertyIndex | getPropertyIndex () const |
| Look up an unnamed property by the type of object it contains, and return its PropertyIndex if it is found. More... | |
| void | updateFromXMLDocument () |
| Use this method only if you're deserializing from a file and the object is at the top level; that is, primarily in constructors that take a file name as input. More... | |
| void | setDocument (XMLDocument *doc) |
| Unconditionally set the XMLDocument associated with this object. More... | |
| const XMLDocument * | getDocument () const |
| Get a const pointer to the document (if any) associated with this object. More... | |
| XMLDocument * | updDocument () |
| Get a writable pointer to the document (if any) associated with this object. More... | |
| Protected Attributes inherited from OpenSim::Function | |
| SimTK::Function * | _function |
| Protected Attributes inherited from OpenSim::Object | |
| PropertySet | _propertySet |
| OBSOLETE: Property_Deprecated set for serializable member variables of this and derived classes. More... | |
| Related Functions inherited from OpenSim::Object | |
| #define | OpenSim_DECLARE_CONCRETE_OBJECT(ConcreteClass, SuperClass) |
| Macro to be included as the first line of the class declaration for any non-templatized, concrete class that derives from OpenSim::Object. More... | |
| #define | OpenSim_DECLARE_ABSTRACT_OBJECT(ConcreteClass, SuperClass) |
| Macro to be included as the first line of the class declaration for any still-abstract class that derives from OpenSim::Object. More... | |
| #define | OpenSim_DECLARE_CONCRETE_OBJECT_T(ConcreteClass, TArg, SuperClass) |
| Macro to be included as the first line of the class declaration for any templatized, concrete class that derives from OpenSim::Object, like Set<T>. More... | |
| #define | OpenSim_DECLARE_ABSTRACT_OBJECT_T(ConcreteClass, TArg, SuperClass) |
| Macro to be included as the first line of the class declaration for any templatized, still-abstract class that derives from OpenSim::Object. More... | |
This class serves as a serializable TendonForceLengthCurve for use in muscle models.
The tendon-force-length curve is dimensionless: force is normalized to maximum isometric force and length is normalized to tendon slack length. The user can adjust the strain the tendon undergoes at 1 unit load (e0), its stiffness at a strain of e0, and the shape of the tendon curve (its 'curviness'):
| strainAtOneNormForce | The tendon strain at which the tendon develops 1 unit of normalized force. strainAtOneNormForce = 0.04 means that the tendon will develop a tension of 1 normalized force when it is strained by 4% of its slack length or, equivalently, is stretched to 1.04 times its resting length. |
| stiffnessAtOneNormForce | The normalized stiffness (slope of the tendon curve) when the tendon is strained by strainAtOneNormForce under a load of 1 normalized unit of force. |
| normForceAtToeEnd | The normalized force developed at the end of the 'toe' region. The toe region lies between 0 strain and some intermediate strain less than the strain required to develop 1 unit of normalized force. The toe region is nonlinear and more compliant than the rest of the tendon curve. |
| curviness | A dimensionless parameter between 0 and 1 that describes the shape of the curve: a value of 0 indicates that the curve is very close to a straight line segment and a value of 1 indicates a curve that smoothly fills the corner formed by the linear extrapolation of 'stiffnessAtOneNormForce' and the x-axis, as shown in the figure. |
Note that we use the Cauchy or engineering definition of strain throughout: strain = (l-l0)/l0, where l is the current tendon length and l0 is its slack length.
Required Parameters
Optional Parameters
Conditions
strainAtOneNormForce > 0 stiffnessAtOneNormForce > 1/strainAtOneNormForce 0 < normForceAtToeEnd < 1 0 <= curviness <= 1
All parameters but the strain of the tendon at 1 unit load (e0) are optional. Note that filling in one optional parameter but not the others will throw an exception when the curve is built. The optional parameters can be used to vary the shape of the curve from a close approximation of a line to a sharply-bent curve.
This curve has the advantage of being C2-continuous, which results in faster simulations when compared to the popular method of using a linearly extrapolated exponential (C0-continuous) curve to parameterize the tendon-force-length relationship. See Millard et al. (2013) for details.
Default Parameter Values If the optional parameters are not specified, the curve is fit to match the average dimensionless in-vivo tendon curve reported by Maganarius et al. and Magnusson et al. In addition, the generated curve will have a characteristic toe region that is fit to the in-vivo literature. Note that this curve is not being fit to the commonly used linearly extrapolated exponential curve documented by Thelen, as it makes the toe region about half as stiff as both the in-vitro and in-vivo data indicate is reasonable. Additionally, the linear section of the curve would be nearly twice as stiff as the data indicates is reasonable.
strainAtOneNormForce ....... 0.049 stiffnessAtOneNormForce .... 1.375/strainAtOneNormForce normForceAtToeEnd .......... 2.0/3.0 curviness .................. 0.5
Example
Note that this object should be updated through the set methods provided. These set methods will take care of rebuilding the curve correctly. If you modify the properties directly, the curve will not be rebuilt, and upon calling a function like calcValue, calcDerivative, or printCurveToCSVFile, an exception will be thrown because the curve is out-of-date with its properties.
References
| OpenSim::TendonForceLengthCurve::TendonForceLengthCurve | ( | ) |
The default constructor creates a tendon-force-length curve using the default property values and assigns a default name.
| OpenSim::TendonForceLengthCurve::TendonForceLengthCurve | ( | double | strainAtOneNormForce, |
| double | stiffnessAtOneNormForce, | ||
| double | normForceAtToeEnd, | ||
| double | curviness | ||
| ) |
Constructs a tendon-force-length curve using the provided parameters and assigns a default name.
| OpenSim::TendonForceLengthCurve::TendonForceLengthCurve | ( | double | strainAtOneNormForce | ) |
This constructor will create a C2-continuous tendon-force-length curve that is fit to match the average dimensionless in-vivo tendon curve reported by Maganarius et al.
and Magnusson et al. In addition, the generated curve will have a characteristic toe region that is fit to the in-vivo literature.
| strainAtOneNormForce | The tendon strain at which the tendon develops 1 unit of normalized force. strainAtOneNormForce = 0.04 means that the tendon will develop a tension of 1 normalized force when it is strained by 4% of its slack length or, equivalently, is stretched to 1.04 times its resting length. |
Conditions
strainAtOneNormForce > 0
| double OpenSim::TendonForceLengthCurve::calcDerivative | ( | double | aNormLength, |
| int | order | ||
| ) | const |
Calculates the derivative of the tendon-force-length multiplier with respect to the normalized tendon length.
| aNormLength | The normalized length of the tendon. |
| order | The order of the derivative. Only values of 0, 1, and 2 are acceptable. |
| double OpenSim::TendonForceLengthCurve::calcIntegral | ( | double | aNormLength | ) | const |
Calculates the normalized area under the curve.
Since it is expensive to construct, the curve is built only when necessary.
| aNormLength | The normalized length of the tendon. |
|
inlineoverridevirtual |
Implement the generic OpenSim::Function interface.
Reimplemented from OpenSim::Function.
References OVERRIDE_11.
| double OpenSim::TendonForceLengthCurve::calcValue | ( | double | aNormLength | ) | const |
Evaluates the tendon-force-length curve at a normalized tendon length of 'aNormLength'.
| void OpenSim::TendonForceLengthCurve::ensureCurveUpToDate | ( | ) |
| SimTK::Vec2 OpenSim::TendonForceLengthCurve::getCurveDomain | ( | ) | const |
Returns a SimTK::Vec2 containing the lower (0th element) and upper (1st element) bounds on the domain of the curve.
Outside this domain, the curve is approximated using linear extrapolation.
| double OpenSim::TendonForceLengthCurve::getCurvinessInUse | ( | ) | const |
| double OpenSim::TendonForceLengthCurve::getNormForceAtToeEndInUse | ( | ) | const |
| double OpenSim::TendonForceLengthCurve::getStiffnessAtOneNormForceInUse | ( | ) | const |
| double OpenSim::TendonForceLengthCurve::getStrainAtOneNormForce | ( | ) | const |
| bool OpenSim::TendonForceLengthCurve::isFittedCurveBeingUsed | ( | ) | const |
| OpenSim::TendonForceLengthCurve::OpenSim_DECLARE_OPTIONAL_PROPERTY | ( | stiffness_at_one_norm_force | , |
| double | , | ||
| "Tendon stiffness at a tension of 1 normalized force" | |||
| ) |
| OpenSim::TendonForceLengthCurve::OpenSim_DECLARE_OPTIONAL_PROPERTY | ( | norm_force_at_toe_end | , |
| double | , | ||
| "Normalized force developed at the end of the toe region" | |||
| ) |
| OpenSim::TendonForceLengthCurve::OpenSim_DECLARE_OPTIONAL_PROPERTY | ( | curviness | , |
| double | , | ||
| "Tendon curve | bend, | ||
| from linear(0) to maximum bend(1)" | |||
| ) |
| OpenSim::TendonForceLengthCurve::OpenSim_DECLARE_PROPERTY | ( | strain_at_one_norm_force | , |
| double | , | ||
| "Tendon strain at a tension of 1 normalized force" | |||
| ) |
| void OpenSim::TendonForceLengthCurve::printMuscleCurveToCSVFile | ( | const std::string & | path | ) |
Generates a .csv file with a name that matches the curve name (e.g., "bicepsfemoris_TendonForceLengthCurve.csv").
This function is not const to permit the curve to be rebuilt if it is out-of-date with its properties.
| path | The full destination path. Note that forward slashes ('/') must be used and there should not be a slash after the last folder. |
The file will contain the following data:
column: 1 | 2 | 3 | 4 data: x | y | dy/dx | d2y/dx2
Samples will be taken from the zero-force region, through the curve, out to strains beyond which the tendon generates normalized forces greater than 1. The curve is sampled quite densely: the tendon-force-length .csv file will have 200+20 rows.
Example To read the .csv file into Matlab, you need to set csvread to ignore the header row. Since csvread is 0-indexed, the following example will begin reading the .csv file from the first column of the second row:
data = csvread('bicepsfemoris_TendonForceLengthCurve.csv', 1, 0);
| void OpenSim::TendonForceLengthCurve::setOptionalProperties | ( | double | stiffnessAtOneNormForce, |
| double | normForceAtToeEnd, | ||
| double | curviness | ||
| ) |
| stiffnessAtOneNormForce | The normalized stiffness (slope of the tendon curve) when the tendon is strained by strainAtOneNormForce under a load of 1 normalized unit of force. |
| normForceAtToeEnd | The normalized force developed at the end of the 'toe' region. The toe region lies between 0 strain and some intermediate strain less than the strain required to develop 1 unit of normalized force. The toe region is nonlinear and more compliant than the rest of the tendon curve. |
| curviness | A dimensionless parameter between 0 and 1 that describes the shape of the curve: a value of 0 indicates that the curve is very close to a straight line segment and a value of 1 indicates a curve that smoothly fills the corner formed by the linear extrapolation of 'stiffnessAtOneNormForce' and the x-axis, as shown in the figure in the class description. |
| void OpenSim::TendonForceLengthCurve::setStrainAtOneNormForce | ( | double | aStrainAtOneNormForce | ) |
| aStrainAtOneNormForce | The tendon strain at which the tendon develops 1 unit of normalized force. strainAtOneNormForce = 0.04 means that the tendon will develop a tension of 1 normalized force when it is strained by 4% of its slack length or, equivalently, is stretched to 1.04 times its resting length. |
1.8.6