Static Meshes¶
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The Static Meshes array on the actor is a list of mesh "layers". Each entry (FSPMeshConfiguration)
lays out one static mesh along the whole spline: the road surface, the left curb, the right curb, a rail,
a pipe. Entries are independent: each has its own spacing, offsets, materials, randomization, and mode.
How a Mesh Fills the Spline¶
- Mesh length — the size of its bounding box along the X axis. The mesh should be modeled along the X axis, with the pivot at its center.
- Step along the spline = mesh length + Spacing. In Curve mode the length is multiplied by Additional Scale X.
- Number of segments = spline length / step (rounded down) + 1. The last segment may go past the end of the spline — in that case it's clamped to the end.
- Distance along the spline is measured in the actor's local units (see section 09).
Mesh Entry Parameters¶
| Parameter | Purpose |
|---|---|
| Design Notes | a free-form note for the designer. |
| Static Mesh | the mesh laid out along the spline. An entry with no mesh is ignored. |
| Mode | Line or Curve for this entry. Only takes effect when the actor's Mode is Use Concrete Mode in Mesh Configuration. See section 04. |
| Spacing | gap between neighboring meshes, cm. A negative value means overlap. |
| Vertical Align | keep the mesh vertical (ignoring the spline's tilt and roll). Line mode only. |
| Additional Offset | offset, cm: X — along the spline, Y — to the right, Z — upward. |
| Additional Scale | additional scale. In Curve mode X also stretches the mesh along the spline (and the step). |
| Additional Rotation | additional rotation. Line — all axes; Curve — Roll only (roll around the spline). |
| Twist Amount | twist: number of full turns around the spline over its whole length. Curve mode only. |
| Receive Decals | whether the meshes receive decals. |
| Materials / Apply Every Index | material overrides — see Materials. |
| Materials Distance Ranges | materials on spline sections — see Materials. |
| Hidden Ranges | sections where meshes aren't created — see section 05. |
| Slot Materials | material for a specific slot on given sections — see Materials. |
| Collision Enabled | mesh collision mode (below). |
| Randomization Settings / Random Seed | scale, offset, and rotation spread — see section 07. |
Offsets¶
- Line. The X offset moves the instance along the spline (by distance), Y and Z — from the point on the spline along its right and up directions. The Z offset is additionally multiplied by the spline point's scale (Z).
- Curve. The X offset shifts the whole segment along the curve (the ends are recomputed on the curve, not extrapolated), Y and Z — in the plane perpendicular to the curve.
Collision¶
| Mode | Line (instances) | Curve (spline meshes) |
|---|---|---|
No Collision |
collision disabled, all channels — Ignore. | all channels — Ignore. |
Query Only / Physics Only / Query And Physics |
the collision profile comes from the mesh, the type from the parameter. | all channels — Block, type from the parameter. |
Static mesh collision depends on the simple collision configured on the mesh asset itself.
Build Order¶
- Mesh entries are processed top to bottom, segments — from the start of the spline.
- In Line mode, instances with the same (entry, materials) are collected into a single
InstancedStaticMeshComponent. - Generated components are attached to the
SplineComponentand recreated on every rebuild. Components you added yourself (in a Blueprint subclass or on an actor instance) are left untouched.