JWSplatt mass runout

JRunout includes two distinct simulation workflows: Rockfall for individual rocks, and JWSplatt for an interacting mass of particles. One JRunout Browser and Native licence covers both; authoring and Cloud solving are free during early access. Both use the shared browser application and project geometry.

Choose the appropriate workflow

Use Rockfall when you need independent rock trajectories and rock-by-rock statistics. Use the Runout controls for the JWSplatt particle workflow, including failure-mass geometry, particle contact, terrain interaction, and bund response.

Prepare and inspect a run

Define the terrain and failure-mass geometry in the shared CAD workspace.
Open the Runout scenario settings and review particle and simulation inputs.
Click Runout Compute in the toolbar to prepare particles and run the physics simulation. To inspect particles before starting, use Prepare in the Runout controls, then Simulate.
Inspect the motion and completed results.

For failure volume and catch capacity alone, hover over Runout Compute and choose Volumetric Compute, or click Compute Volumetrics in the Runout Results pane. The toolbar dropdown also opens on keyboard focus. This draws the capacity polygon and projected line without generating particles or running physics, using the selected compute location. Capacity and the line continue to update as you edit the geometry or volumetric settings. An explicit Cloud computation enables these live updates for the current project.

The line starts at the selected Berm's highest point and rises at the Runout Angle above horizontal, toward the side containing the Toe Point. Without a Toe Point, the app uses the mean of the Failure Mass vertices and shows a warning. Project to Backscarp changes the boundary used for intersection by removing the Failure Mass from the External Boundary.

Click Remove Particles after preparation or simulation to clear the particles and physics results while retaining your geometry, settings, and volumetrics. Edits will not generate particles again until you click Prepare or Simulate. This removal choice lasts for the current project session. While preparing, simulating, or in Tank mode, use Stop or Exit Tank Mode before removing.

Remove Volumetrics (runout.volumetric.clear) clears the active scenario's volumes, capacity polygon, projected line and volumetric warnings while retaining particles and physics measurements. Live volumetric updates remain paused for that scenario during the project session until Compute Volumetrics, Prepare or Simulate is explicitly started. Removal is unavailable during computation or Tank mode.

The Runout interface also includes calibration tools. Review their target geometry and parameters before using the resulting settings in another model.

Choose a compute path

Open Configure → Project Settings → Runout and choose Solver mode. Exact is the default CPU solver. WebGPU enables experimental GPU compute on this device for Runout simulations and calibration. It supports the same particle settings, including irregular fragments; results can differ from Exact because the GPU solves contacts differently. Small scenes can run slower on WebGPU; Exact remains the default.

The WebGPU option becomes available after the browser finds an adapter. If WebGPU is unavailable, the dialog explains why. Select a CPU mode to run on that device. The choice applies to every Runout scenario, is saved in the project, and supports undo and redo. Changing it clears Runout simulation results while retaining prepared particle packing.

Solver iterations and convergence

Open Configure → Project Settings → Runout to set the maximum position and velocity iterations per simulation step. The defaults are 6 position and 4 velocity passes; both accept integers from 1 to 1000.

Each solver also has a convergence tolerance. A positive value enables early exit after a complete pass meets the criterion:

Position tolerance (m): the largest remaining contact penetration beyond the allowed, timestep-scaled slop must be within tolerance.
Velocity tolerance (m/s): for each particle, the solver adds the magnitudes of speed changes from contact corrections, including translation and rotation at the outer edge. The largest particle total must be within tolerance. This prevents opposing contact corrections from cancelling in the convergence check.

Both tolerances default to 0, which disables early exit and uses the full iteration count. Reaching the maximum continues the simulation even when the chosen tolerance is not met. Higher limits or smaller positive tolerances can increase computation.

These settings apply to all Runout scenarios and calibration runs and are saved with the project. Applying a change clears Runout results and keeps prepared particle packing available for reuse. Undo and redo restore the settings.

For the independent-rock workflow, start with First rockfall simulation.