• New project — import an FDS input file from the Input section. PluMesh reads the file and automatically extracts the geometry, surfaces, and mesh domain.
• Saved project — open a previously saved .plumesh project file to reload your full session and continue where you left off.

• Base Cell Size — the coarsest cell size used across the domain. All refined regions are derived from this value.
• Min Cells per Axis — the minimum number of cells required along any axis of a mesh block. Prevents blocks from becoming too thin.
• Merge Gap — mesh blocks separated by a gap smaller than this value will be merged together automatically.
• Max Aspect Ratio — limits the ratio between the longest and shortest axis of a mesh block, preventing blocks from becoming too elongated.

Select a named surface from your FDS file and assign a refinement factor. Padding defines how far the refined mesh zone extends beyond the surface in each direction (±X, ±Y, ±Z), concentrating fine cells exactly where the simulation demands it. Padding values are multiples of the base cell size.

Define a custom rectangular refinement region anywhere in the domain with its own refinement factor and region coordinates — independent of any FDS surface. Useful for refining areas of interest that have no named surface but require higher resolution.

PluMesh automatically splits and distributes mesh blocks across a configurable number of MPI processes using a load-balancing algorithm.

• Number of Processes — how many MPI processes to distribute the mesh across.
• Max Deviation (%) — the maximum accepted load imbalance between the heaviest and lightest process.
• Max Mesh Count — a hard cap on the total number of mesh blocks, preventing excessive splitting.

The output report shows the cell count per process and load deviation, giving full visibility into the partition quality.

Adds a surrounding coarse mesh layer outside the main simulation volume — ideal for open-boundary conditions and building surroundings.

• Cell Multiplier — defines the outer cell size as a multiple of the base cell. A multiplier of 3 means outer cells are 3× coarser than the inner mesh.
• Inner Domain — the bounds of the core simulation volume (Xmin, Xmax, Ymin, Ymax, Zmin, Zmax). The outer shell fills the space between this boundary and the full FDS domain.

• Edit — select any mesh block to split it along an axis, resize it, or rename it. All changes reflect instantly in the 3D viewer.
• Add / Delete — create new mesh blocks manually by defining coordinates, or remove blocks you no longer need.
• Merge — select two adjacent mesh blocks at the same time and the merge option appears automatically. If they share a face and have matching cell sizes, PluMesh combines them into a single block.
• Overlap Checker — scans all mesh blocks and reports any volumetric overlaps, ensuring a clean mesh before export.
• Alignment Checker — verifies that touching mesh blocks have compatible cell sizes at shared faces (integer ratio required by FDS), flagging node mismatch errors before they reach the solver.

Once the mesh is finalised, click Export. PluMesh writes the complete MESH blocks directly back into your original FDS input file, replacing any previous mesh configuration. The rest of your file — geometry, materials, boundary conditions, and outputs — is left entirely untouched and ready for simulation.