Absolute Nodal Coordinates — RibleANCF
RibleANCF is the flexible-body extension package for absolute nodal coordinate formulation support in the Rible monorepo.
Flexible Beam and Cable
The implementation includes the unconstrained reduced-order 3D beam/cable family (ANC3DRURU), with element coordinates laid out as e = [r_i; r_x_i; r_j; r_x_j] and cubic Hermite-like interpolation along the centerline.
Thin-Shell Families
RibleANCF supports thin-shell S1 mechanics for both rectangular and triangular topologies:
Rectangular Shell (
ANC3DRectShell2433): 4-node quadrilateral element with position and two in-surface slope vectors per node.Triangular Shell (
ANC3DTriShell2333): 3-node triangular element using a 9-term Pascal-row polynomial basis.
Builtin simple mesh generation is provided for rectangular and triangular patches.
Interoperability and Visualization
RibleANCF integrates with the Meshes.jl ecosystem for geometry operations and uses the root Vis recipe system for rendering.
Beam Visualization: Renders as a tube around the deformed reference curve.
Shell Visualization: Renders as a deformed surface mesh evaluated from the element shape functions.
Both beam and shell bodies can be rendered using the standard vis and vis! commands:
using Rible, RibleANCF, CairoMakie
# ... build ANCF body ...
vis(body)Coordinate Interface
Unlike rigid-body NCF coordinates, the current ANCF implementation has no intrinsic coordinate constraints. It follows the same top-level coordinate-interface contract used by Rible, but the intrinsic constraint methods intentionally degenerate to zero-size or no-op behavior.