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--- visual3d:documentation:pipeline:force_commands:entering_inertial_values_using_expressions [2024/06/26 20:05] – removed sgranger
+++ visual3d:documentation:pipeline:force_commands:entering_inertial_values_using_expressions [2025/09/11 00:59] (current) – Made images visible. wikisysop
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+====== Entering Inertial Values Using Expressions ======
+It is possible to include any regression equations for the inertia and center of mass because Visual3D allows the user to put [[visual3d:documentation:pipeline:expressions:expressions_overview|expressions]] into the edit boxes.
+===== Example: Typical Right Thigh Segment =====
+Consider a typical right thigh segment, which is populated with the default inertial values.
+{{:InertiaExpression1.jpg}}
+If the user selects this segment to be a CUSTOM_SEG, the edit boxes can be edited.
+{{:InertiaExpression2.jpg}}
+===== Example: Frustra of Right Cones =====
+In this example we consider a conical segment:
+{{:frustraofrightcones1.gif}}
+We will create an expression for the Axial component of the center of mass based on the default computations described [[visual3d:documentation:modeling:segments:segment_inertia#inertial_properties_of_a_cone_conical_frustrum|elsewhere in the documentation]].
+{{:frustraofrightcones2.png}}
+For convenience create a new Subject Metric X and enter the following expression:
+<code>
+RTH_DISTAL_RADIUS/RTH_PROXIMAL_RADIUS:
+</code>
+{{:InertiaExpression3.jpg}}
+We can then use the Subject Data Metric X that we just created in another expression. Enter the following expression into the Segment Properties Axial edit box:
+<code>
+(1+2*X+3*X^2)/4/(1+X+X^2)*RTH_SEG_LENGTH
+</code>
+{{:InertiaExpression4.jpg}}
+**Note**: the edit box doesn't show the entire expression, which is a nuisance