paraview-exodus

# Visualize ExodusII files with ParaView Drives ParaView's Python interface (`paraview.simple`, run via `pvpython`) to render an ExodusII mesh colored by a field, and `ffmpeg` to turn a multi-timestep series into a video. Assumes `pvpython` and `ffmpeg` are on the PATH. ## How to use it Two scripts in `python/paraview_exodus` of the MOOSE repository do the work: `render_exodus.py` renders the frames under `pvpython`, and `visualize_exodus.sh` runs the renderer and then encodes the frames into MP4 when the file has multiple timesteps. `visualize_exodus.sh` is the entry point, so point `V` at it, using `$MOOSE_DIR` or the path to the MOOSE checkout in play: ```bash V=$MOOSE_DIR/python/paraview_exodus/visualize_exodus.sh # Most basic — color by the first non-ID field, default viridis colormap, white background $V path/to/result.e # Specify field and colormap $V result.e --field temperature --colormap coolwarm # Custom background and resolution $V result.e --field disp_x --background "#202020" --resolution 1280x720 # Fit the frame to the mesh shape (good for long/thin or wide domains) $V result.e --field disp --auto-aspect ``` The wrapper locates `render_exodus.py` next to itself, so invoke it by path from whatever directory holds the exodus file. Outputs are written to the current working directory using the input's basename unless `--output` is given. `render_exodus.py` is also usable on its own (`pvpython render_exodus.py ...`) for a single image or a frame series without the ffmpeg step. **Before rendering an unfamiliar file, list its fields** so you pick a real one: ```bash $V result.e --list-fields ``` ## Behavior - **Single timestep** → one image, `PREFIX.png`. - **Multiple timesteps** → ParaView writes `PREFIX.0000.png …`, then ffmpeg encodes `PREFIX.mp4`. Intermediate frames are deleted unless `--keep-frames`. - Frames are rendered directly at the requested resolution (default 800×600). ffmpeg only rounds dimensions to even numbers (`scale=trunc(iw/2)*2:...`), a yuv420p requirement; it does not rescale. - Color range defaults to **fixed over all timesteps** so colors are comparable frame to frame (`--rescale per-frame` to recompute each frame). - 2D meshes (flat in z) are auto-detected and rendered with parallel projection. - `--auto-aspect` reshapes the frame so the mesh fills it instead of floating in empty background; `--resolution` then acts as the bounding size. It works by a **probe pass**: every frame is rendered (off-screen, no legend) and the actual mesh silhouette is measured, then unioned across all frames. Because it measures rendered pixels rather than reported bounds, it correctly contains meshes that **deform or move** over time (e.g. a bending beam) — the frame fits the mesh at every timestep, not just the first. Cost: it renders the series twice (probe + final). Requires Python PIL/Pillow in `pvpython`; if missing, it falls back to the fixed `--resolution`. ## Options Renderer (`render_exodus.py`), all forwarded by the wrapper: | Option | Default | Meaning | | - | - | - | | `--field NAME` | first available that is not an ID | Field/variable to color by | | `--component C` | `Magnitude` | Vector component: `Magnitude`, `X`/`Y`/`Z`, or index | | `--colormap NAME` | `viridis` | Short name or any ParaView preset (see below) | | `--invert-colormap` | off | Reverse the colormap | | `--background COLOR` | `white` | `name` \| `#rrggbb` \| `r,g,b` (also `transparent`) | | `--text-color COLOR` | `auto` | Scalar bar / axis text; `auto` contrasts with the background | | `--resolution WxH` | `800x600` | Output resolution (bounding size if `--auto-aspect`) | | `--auto-aspect` | off | Probe all frames; reshape so the mesh fills the frame | | `--output PREFIX` | input basename | Output name (no extension) | | `--rescale fixed\|per-frame` | `fixed` | Color range strategy | | `--no-scalar-bar` | shown | Hide the color legend | | `--no-edges` | shown | Hide element/mesh edges | | `--edge-color COLOR` | black | Edge color when edges are shown | | `--orientation-axes` | off | Show the orientation triad | | `--list-fields` | — | Print available point/cell fields and exit | Wrapper-only: | Option | Default | Meaning | | - | - | - | | `--fps N` | `15` | Animation frame rate | | `--keep-frames` | off | Keep intermediate PNGs | | `-- <ffmpeg args>` | — | Everything after `--` is passed verbatim to ffmpeg | ## Colormap names Short aliases: `viridis`, `plasma`, `inferno`, `magma`, `cividis`, `coolwarm`, `coolwarm-extended`, `jet`, `rainbow`, `turbo`, `blackbody`, `grayscale`, `xray`. Any other value is passed straight to ParaView's `ApplyPreset`, so full preset names like `"Cool to Warm (Extended)"` or `"Black-Body Radiation"` also work. ## Notes for the assistant - If the user names a field, pass it through; if unsure it exists, run `--list-fields` first and report the options. - Vector fields (e.g. displacement) default to magnitude; use `--component` for a single component. - To pass extra ffmpeg flags (codec, quality), append them after `--`, e.g. `-- -crf 18 -c:v libx264`. - Report the final output path(s) to the user when done. - `python/doc/content/python/paraview_exodus.md` is the user-facing page for these scripts, and `python/paraview_exodus/tests` holds their unit tests. A change to either script belongs with an update to both.