The vehicle floated 3.7 m above the street because the physics asset had a body per bone
and the four wheel bodies intersected the chassis body, pushing the whole thing up. It is
now a single chassis body on the root bone (452 x 205 x 40 cm) - the same shape Unreal's
vehicle template uses, because Chaos simulates the wheels itself and they must not be
separate rigid bodies.
Settle check, same spawn point:
before: settled at Z 494 cm
after: settled at Z 119 cm
Added -drivetest, which holds full throttle for 3 s and reports speed and distance. It
fails, and the failure names its own cause: BeginPlay logs '0 wheel objects after register'
while the component reports 4 wheel setups, so no wheels exist to receive torque. Recorded
in TODO.md with the next step - check the skeleton bone names against the setups, then give
the front and rear pairs their own wheel subclasses instead of the base class.
The physics asset could not be made from Python (PhysicsAssetFactory exposes no mesh
property), so a small editor-only C++ helper calls FPhysicsAssetUtils::CreateFromSkeletalMesh
- the same code path as the editor's Create Physics Asset action. It produces
PA_Vehicle_Sedan with 6 bodies and assigns it to SK_Vehicle_Sedan.
AGigLineVehicle is a Chaos wheeled pawn that configures its four wheels from the modelled
dimensions (radius 33 cm, wheelbase 278, track 156) and is staged in DemoMap. A run logs:
spawned at (-12950, -900, 120), 4 wheel setups
settled at Z 494 cm, simulating=1, speed=0 cm/s
That last line is the defect and it is not hidden: the vehicle rests 3.7 m above the road,
so the generated physics bodies do not match the mesh. Recorded in TODO.md with the next
step - inspect the bodies against the mesh, then either fix the creation params or author
two boxes and four wheel spheres explicitly.
Chaos drives a skeletal mesh, so the static system split was not drivable on its own. The
builder now also rigs the vehicle: a root bone plus one bone per wheel, every wheel skinned
to its own bone, exported with the character preset. SK_Vehicle_Sedan imports with
SK_Vehicle_Sedan_Skeleton (508 triangles).
Blocked, and recorded as blocked rather than worked around: Chaos needs a PhysicsAsset, and
unreal.PhysicsAssetFactory in 5.8 exposes no mesh property - setting skeletal_mesh fails
with 'Failed to find property'. Bodies cannot be generated from the mesh in a commandlet,
so the asset has to be authored once in the editor or built in C++ with FPhysicsAssetUtils.
Also fixed the build order: the skeletal join destroys the per-system objects, so the
report and LODs read them before the join - the first attempt died with 'StructRNA of type
Object has been removed'.
Follows the vehicle-artist object split, which the first build violated: body, glass,
front and rear lights, mirrors and a single wheel mesh are now separate objects and
separate assets in /Game/Hollywood/Vehicle. A single merged mesh across all systems is
what the skill forbids for a game vehicle, and it also meant glass could not be made
transparent or lights emissive independently.
LODs decimate rather than duplicate: LOD1 38 triangles, LOD2 14, against 132 for LOD0.
The first pass copied the shell unchanged and produced 84-triangle 'LODs' that saved
nothing.
Imports verified with bounds: body 4.76 x 1.76 x 1.28 m, wheel 0.22 x 0.66 x 0.66 m,
which match the modelled dimensions.
Open, recorded: LOD group wiring needs StaticMeshEditorSubsystem.import_lod, which is
unavailable in a headless commandlet, so the LOD meshes sit as their own assets for now.
zwitschi