Output fields

The optional top-level output section selects which fields are written to the Exodus output file. Output cadence is controlled separately by output interval — see Mesh and output files.

output:
  velocity: true
  acceleration: true
  stress: true
  deformation gradient: false
  internal variables: true
  recovery: lumped

Key	Type	Default	Description
`velocity`	bool	`false`	Nodal velocity. Dynamic integrators only.
`acceleration`	bool	`false`	Nodal acceleration. Dynamic integrators only.
`stress`	bool	`true`	Per-quadrature-point Cauchy stress.
`deformation gradient`	bool	`true`	Per-quadrature-point deformation gradient.
`internal variables`	bool	`false`	Per-quadrature-point constitutive state.
`recovery`	string	`lumped`	Nodal projection method for element fields.

Stress and deformation gradient are on by default

Omitting the output section does not give you a displacement-only file. stress, deformation gradient, and lumped recovery are enabled by default, which on a large mesh is a substantial amount of data. Set them to false explicitly for lean output.

Keys in this section are validated, so a misspelling produces an unknown-key warning with a suggestion.

Always written

Displacement and the time value are written unconditionally, regardless of the output section:

Variable	Meaning
`displ_x`, `displ_y`, `displ_z`	Nodal displacement components

Gated nodal fields

Variable	Written when
`velo_x`, `velo_y`, `velo_z`	`velocity: true` and the integrator is dynamic
`acce_x`, `acce_y`, `acce_z`	`acceleration: true` and the integrator is dynamic

Under quasi static these flags have no effect — there is no velocity or acceleration state to write.

Element fields

Element variables carry a trailing quadrature-point index _1, _2, … The index suffix is deliberate: it stops ParaView from auto-grouping the components into a tensor it would then mislabel.

Field	Names	Component order
Stress	`sigma_xx_q` … `sigma_zz_q`	`xx, xy, xz, yy, yz, zz` (symmetric)
Deformation gradient	`F_xx_q` … `F_zz_q`	`xx, yx, zx, xy, yy, zy, xz, yz, zz`
Internal variables	`<name>_q`	From the constitutive model, e.g. `eqps_1`

`F` component order is column-major

The deformation-gradient components are written in column-major order, so the first index is the row: F_yx is component (2,1), not (1,2). Stress is symmetric so its ordering is unambiguous.

The number of quadrature-point suffixes follows the quadrature rule. Names are registered for the block with the most quadrature points, so on a mixed mesh some names may exist without values in blocks that have fewer.

Internal variables are emitted only when the constitutive model actually has state — an elastic model produces none regardless of the flag.

The entire element-field block, including the GPU-to-host transfer of the state array, is skipped when stress, deformation gradient, and internal variables are all false. On GPU runs that transfer is the dominant output cost, so turning these off is worth doing when you do not need them.

Recovered nodal fields

Element quantities live at quadrature points; recovery controls how they are projected to nodes for visualization. Recovered variables take a trailing _n.

`recovery`	Aliases	Method
`lumped`	—	Diagonal (lumped) projection. Fast, slightly smoothing. Default.
`consistent`	`l2`	Full consistent-mass L2 projection. More accurate; requires a Cholesky factorization at setup.
`none`	—	No projection; skip recovered output.

Variable	Written when
`sigma_xx_n` … `sigma_zz_n`	`recovery` ≠ `none` and `stress: true`
`<name>_n`	`recovery` ≠ `none` and `internal variables: true`

The value is lowercased and trimmed before matching, so Lumped and L2 are fine. An unrecognised value is a hard error naming the supported set:

Unknown output.recovery = "lmped". Supported: "lumped", "consistent" (alias "l2"), "none".

Recovered deformation-gradient names are declared but never written

With deformation gradient: true and recovery enabled, F_*_n variables appear in the Exodus file's variable list but are never populated. Use the per-quadrature-point F_*_q values instead.

Naming summary

Suffix	Meaning
(none)	Nodal primary field — `displ_x`, `velo_y`, `acce_z`
`_1`, `_2`, …	Element value at that quadrature point
`_n`	Nodal value recovered by L2 projection