2. Scale and units

Model at real size

Build the truck, trailer, or machine at factory scale. A 15.5 m low loader is 15.5 meters long in Blender, not 15.5 centimeters and not 1,550 meters. A steer tire that is 126 cm tall in real life has a radius of 0.63 m in Blender.

Blender scene settings

• Scene properties → Units: Metric, Unit Scale 1.000000, Length Meters.
• Every object’s scale should be 1, 1, 1. When the model looks right, use Apply Scale and Apply Rotation (Ctrl-A) so there is no hidden transform left on the object.
• Leave Location alone until the origin is where you want it, then you can Apply Location if you need the origin baked.

What “centimeters in the data file” means

The vehicle data (the sidecar *_ue.json, the equipment definition, and the New Equipment window) stores positions in centimeters, in Unreal space (X forward, Y right, Z up). A hub at 2.52 m in front of the origin and 1.07 m to the left becomes [252, -107, 83] in that file. You do not type that by hand if you run the export script on your empties — but if you do, do not multiply by 100 a second time. The reader already expects centimeters.

3. Axes, export direction, and origins

Which way is forward?

In the game and in every equipment data file, the convention is:

FBX export direction (new models)

For a new model built in Blender at real size, use the standard Unreal settings:

• Forward: −Z Forward
• Up: Y Up
• Apply Scalings: FBX All
• Scale: 1.00  ·  Apply Unit on  ·  Use Space Transform on

Those settings are what the project’s trailer export script uses. After import, the front of the vehicle must point down Unreal’s +X, the roof up +Z, and a 1-meter feature must measure about 100 cm. If something comes in sideways or mirrored, fix the export or the import “Force Front X Axis” checkbox — do not scale the mesh to compensate.

Where to put the origin (pivot of the whole model)

Unreal +X is also how automatic fallbacks work today: if a trailer has no kingpin socket, the hitch code looks toward the front of the bounds (+X) and insets about 40 cm. A well-placed RECEIVER_Kingpin empty is always better than that guess.

4. Standard names

Use these names when they fit. They are the shared language between Blender empties, the export script (~/TerraGenesis_ModKit/blender_export_empties.py), the New Equipment window, and the game. Write them in this capitalization (CamelCase after the prefix). Matching is case-insensitive, and Blender’s .001 suffixes are dropped, so ATTACH_FifthWheel.001 still counts as ATTACH_FifthWheel.

The export script reads empties whose names start with TIE_, SLOT_, ATTACH_, RECEIVER_, or WHEEL_ (any suffix after the prefix is fine), plus an optional ENTER empty and a ROOT object for the origin. Positions are written in Unreal centimeters, relative to ROOT if it is in the scene, otherwise the world origin.

Wheels

Name the empties with the uppercase WHEEL_ prefix. That is what the export script looks for.

Left is Unreal −Y (Blender −X on a Z-up vehicle). Put the empty at the hub center, not on the ground and not on the outside face of the tire. A second fifth wheel or a second wheel of the same name uses a _2 suffix, for example WHEEL_R3L already distinguishes axles; ATTACH_FifthWheel_2 is the pattern for two attachers of one type.

Attachers and receivers

The towing side (a truck, or the rear of a trailer that can pull another) gets ATTACH_<Type>. The towed side (the front of a trailer) gets RECEIVER_<Type>. A trailer’s kingpin is RECEIVER_Kingpin — never ATTACH_Kingpin. A trailer can hold both a receiver in front and an attacher at the rear.

Those five pairs are the built-in standard. There is no Drawbar or Clevis type in the list. A converter dolly is just a short trailer with RECEIVER_Lunette at the front and ATTACH_FifthWheel at the rear. A Super B lead trailer has RECEIVER_Kingpin at the front and ATTACH_FifthWheel at the rear. Need a second attacher of the same type? Add _2, _3, and so on (ATTACH_FifthWheel_2).

Today a truck with “Has Fifth Wheel” on can still couple a semi at the Kingpin socket, and rear hitch type (for example Pintle) can already be stored on the equipment definition. Put the approved empties on every new model now; the data-driven hitch list will read them.

Accessory slots Types work now

These are the slot types the game already knows. A truck can have any number of slots, including several of the same type (two toolboxes, left and right exhaust, many light pads). Give each slot its own empty and its own name, starting with SLOT_.

The Modder Kit already ships placeholder blocks at ~/TerraGenesis_ModKit/Generated/Blocks/SLOT_<Type>.fbx. Each block is the right size, with a bump that points forward (+X) and the pivot at the slot origin. Snap your part to the block, then delete the block before you export.

Tie points Written, not yet tested

Tie points can come from, in this spirit: the New Equipment window’s Tie points (trailers) tab (the tab is written, not compiled or tested yet), tie_points in a mod vehicle JSON, TIE_ empties from the export script, mesh sockets TIE_* / TieDown*, or automatic deck-edge points if nothing else is set.

Play plan Written, not yet tested: F on foot at a point does up or undoes that one point. F in the cab does up or undoes every point at once. Chains are for machines and trucks; straps are for cargo. When every point on a load is done, the load is locked to the deck. There is no warning and no speed limit for an unsecured load.

Lights Recommended empty names

The export script does not yet collect LIGHT_ empties (it reads TIE_, SLOT_, ATTACH_, RECEIVER_, and WHEEL_). The vehicle already has light sockets you can list on the equipment definition. The empty names below are still the standard to put in Blender so a later pass, or a hand edit, can fill those lists.

Other useful names

5. Custom names

The standard list is a starting point, not a cage. If you are building a logging bunk, a hay spike, a spreader bar, or a hitch that isn’t one of the five built-in pairs, you can make up a clear name and register it in data. You should not need a code change.

How to invent a name

• Keep the prefix so the export script and the game know what the empty is for: ATTACH_ (towing), RECEIVER_ (towed), SLOT_, WHEEL_, TIE_. ROOT and ENTER are fixed names, not prefixes. LIGHT_, CYL_, and TOOL_ are useful in the .blend even though the current export script does not collect them.
• After the prefix, use letters, digits, and underscores only, 1 to 32 characters. No spaces. CamelCase is recommended: ATTACH_LoggingBunk, SLOT_Winch, TIE_Bunk_L1, RECEIVER_LoggingBunk.
• Matching is case-insensitive. Blender’s .001, .002 suffixes are dropped, so a duplicated empty is not a new type.
• To have more than one of the same type, add _2, _3, and so on: ATTACH_FifthWheel_2, SLOT_Toolbox_2.
• Make the name describe the joint or the part, not the truck. ATTACH_Pintle can live on many vehicles; ATTACH_MyT800Thing should not.
• Do not reuse a standard name for a different meaning. If you need something new, pick a new word.
• For a custom type, pair ATTACH_YourName with RECEIVER_YourName (same type word on both sides) and list what it can couple to in the hitch-type data.

Where you define it Approved, being implemented

Custom hitch types are declared in one of two places, with no C++ work:

• New Equipment window — the Hitch types list (Tools → TERRA GENESIS → New Equipment…).
• Mod JSON under Mods/<mod>/Hitches/*.json. A file holds a hitch_types list. Each type has a name, a side (towing, towed, or both), compatible types it may couple to, yaw / pitch / roll limits, a couple radius, and a joint style. Vehicle files in Vehicles/*.json get attachers and receivers arrays (the export script already writes those keys).

What already works today, without a new type

• Custom slot names of an existing type. You can add SLOT_Toolbox_L and SLOT_Toolbox_R as two slots of type Toolbox, or thirty Lights pads, each with its own location. The slot’s name is free; the type must be one of the types in section 4 until custom slot types ship.
• Extra wheel empties following the R-series or T-series pattern. There is no fixed axle cap in the naming.
• As many TIE_ points as the deck needs, with any suffix.

6. Object, mesh, and hierarchy naming

Unreal and the export scripts are much happier with plain, unique names: letters, digits, and underscores. Avoid spaces in names you want the game to find (5th wheel on a converted truck works only because a special-case script looks for it — don’t add more of those).

Suggested mesh names

Hierarchy

• Armature (if skeletal) at the vehicle origin, rest pose already correct, no leftover rotation on the armature object.
• Body mesh parented to the armature (skeletal) or sitting at the origin (static).
• Wheels as separate meshes — not joined into the body.
• Split accessories (bumper, visor, exhaust, rack) as their own objects, still in the same scene position they had on the truck. When they are exported alone, they keep that same world position so a 0,0,0 slot places them correctly. This is how the T800 bumper and exhaust split is set up.
• Empties either at the root or parented to the part they belong to (a boom empty should follow the boom). The export script writes each empty’s position relative to ROOT (or the world origin if ROOT is missing), so parenting is for your sanity, not a requirement.
• Collision boxes parented to, or sitting with, the mesh they describe.

7. Wheels

Rules that matter in-game

• One wheel mesh per corner (or a shared L/R mesh instanced at each empty). Duals can be one mesh that includes both tires, still pivoted at the hub, or two meshes — pick one style and stick to it.
• Pivot at the hub center. Apply transforms so the wheel object’s origin is the spin axis.
• Do not bake wheels into a trailer or body mesh if they should spin. The current low loader and Talbert RGN have baked wheels, so those wheels stay still. New models should not repeat that.
• Left and right. The shared Alcoa sets have separate left and right meshes. Face the outside of the wheel outward. If a mesh comes in facing inward, the wheel set has an extra-yaw field — but it is better to fix the mesh.
• Converted wheel FBXs in this project often have their axle along X and use a 90° yaw in the wheel-set data so Unreal’s wheel axle (+Y) lines up. If you model a new wheel, you can either match that or model with the axle already on Y and leave the extra rotation at 0. Check a test import; do not guess twice.

Shared Alcoa wheels — do not modify

The project has a shared semi wheel set. Reuse it on new trucks and trailers when the size is right. Do not edit these files to suit one model; you would change every truck that uses them.

If a truck needs a different size or style, make a new wheel set and new meshes. Leave the Alcoa files alone. Hide any tires that are modeled into the body (the wheel set can hide named bones or material slots) so you do not see two tires in the same place.

The game does not use engine motion blur (it is off project-wide), so a very low-segment tire will look faceted at speed. Give the tread and rim enough segments to read as round, but there is no need for a race-sim wheel.

8. Empties: placement, orientation, and display

Empties are how you tell the game where wheels, hitches, slots, ties, lights, doors, and cylinders are, without building that into the mesh. Name them from the standard (or custom) list, leave them at factory scale (1,1,1), and include a ROOT object at the vehicle origin. Run ~/TerraGenesis_ModKit/blender_export_empties.py to write the JSON (you can also pack the empties into the FBX).

Display tips in Blender

• Viewport display: Plain Axes or Arrows, size about 0.2 to 0.5 m so you can see them next to a truck but they don’t fill the screen.
• Put empties in a collection named Empties or Sockets. Hide the collection from render; keep it visible while you work.
• A different color or a short custom shape per family (wheels, attachers, ties) helps when the deck is crowded.
• Lock scale. If you accidentally scale an empty, Apply Scale or reset it to 1.

Orientation rules

• Align each empty to the vehicle: no random tilt. After import, its local +X should match the vehicle’s forward, +Z up, unless the point has a real facing of its own.
• Headlights and work lights should shine forward (Unreal +X, which is Blender +Y before export). Point the empty’s local forward that way.
• Tail lights face rear (Unreal −X).
• Attachers and receivers sit on the coupling: the fifth-wheel empty on the plate, at hook height; the kingpin empty on the pin axis, at the height the plate should meet. A pintle empty sits in the throat of the hook. Rotation 0,0,0 in vehicle space is the default unless the hook itself is rotated.
• Slots use the same space as the truck (cm, X forward). The ModKit block’s bump points forward. A part modeled on that block, with the same pivot, drops in cleanly. The T800 factory bumper and exhaust use a zero offset because the part was cut from the body and left in place.
• Tie points sit on the deck surface, just inboard of the side rail, where a hook would land — not floating a meter in the air and not buried under the deck.
• Wheel empties at hub center, with the empty’s axes lined up with the vehicle (spin is handled by the game).

The export script writes each empty’s position (and rotation when it matters) into JSON, already converted to Unreal centimeters, relative to ROOT. It collects TIE_, SLOT_, ATTACH_, RECEIVER_, and WHEEL_ empties, plus ENTER. Run it in Blender with blender my_model.blend --background --python ~/TerraGenesis_ModKit/blender_export_empties.py -- out.json, or paste the script into the Text Editor and press Run (it writes <blend name>_empties_ue.json next to the .blend). You can also enter positions in the New Equipment window (slots, Hitch types, Tie points (trailers), fifth-wheel rest height, rear hitch location).

9. Attachers, receivers, and trailer chains

What works today

• A truck with Has Fifth Wheel on can couple a semi trailer. The plate is a slidable fifth-wheel component; the trailer is held at a Kingpin socket (or a tagged component, or a bounds guess). Put ATTACH_FifthWheel and RECEIVER_Kingpin empties on new models anyway.
• The hitch key is H. Once chaining ships, H couples the nearest compatible free pair anywhere in the chain; if nothing is in reach, H unhooks the last trailer. Brakes, lights, and ABS pass down the chain.
• The Kenworth 521 has Has Fifth Wheel off and a pintle point at the rear (from SOCKET_Attacher_PanelHitch in its converted file). It cannot pull a fifth-wheel low loader or RGN. Rear hitch type can already be stored as a name such as Pintle. Use ATTACH_Pintle on the truck and RECEIVER_Lunette on the trailer.

What to model for every new truck or trailer

• Place the approved empties even if a type’s gameplay is still being implemented. A pole trailer should have RECEIVER_PoleReach at the front (or RECEIVER_Lunette, if that is the real joint) and, if it can lead another trailer, a rear ATTACH_… as well.
• Height matters. Measure the real fifth-wheel or pintle height and put the empty there. A kingpin that is 20 cm too high will stand the trailer on its nose or hang it in the air.
• If the fifth wheel slides, the rest position is the empty (or the rest position in data). Slide limits are stored in centimeters along X (the T800 slides roughly from −598 to −346 cm, resting near −511).

Chains of trailers — Super B, dollies, and up to six Approved, being implemented

The rule for new trailers: a trailer may have a receiver in front and its own attacher at the rear. That is how a Super B (B-train) works — the lead trailer has RECEIVER_Kingpin and a rear ATTACH_FifthWheel; the second trailer’s RECEIVER_Kingpin can hook to the lead or directly to a truck. A converter dolly is the same idea with different types: RECEIVER_Lunette in front and ATTACH_FifthWheel at the rear, so a pintle truck can pull a fifth-wheel trailer.

The game will allow a chain of up to six trailers. H couples the nearest compatible free pair anywhere in the chain. If nothing is in reach, H unhooks the last trailer. Brakes, lights, and ABS pass down the chain. This behavior is approved and being implemented.

New hitch types (a logging bunk pin, anything we have not listed) follow section 5: ATTACH_YourName on the towing side, RECEIVER_YourName on the towed side, declared in Mods/<mod>/Hitches/*.json or the New Equipment Hitch types list, with no code change.

10. Collisions

Keep the simple boxes

Your FS25 habit of building a few boxes, not a high-poly “accurate” collision mesh, is the right one. Unreal wants convex primitives. They are faster and they behave more predictably than using the visible model as collision — and a decorative bumper or a chain should not be what a tire drives on.

Naming (static meshes, including most trailers, decks, ramps, and accessories)

Put the boxes in the same FBX as the visible mesh. Unreal reads them automatically when the name matches this pattern:

• The text after the prefix must be the exact visible mesh name, then _01, _02, … If the mesh is front_bolster, the boxes are UCX_front_bolster_01, UCX_front_bolster_02. UCX_front_bolster_bottom is not picked up unless the mesh is literally named front_bolster_bottom.
• Each box must be convex (a regular Blender cube is). Do not use a C-shaped or hollow mesh as one UCX piece — split it into convex bits.
• Deck and ramp tops must be flat and level along the driving surface. That plane is what trucks and loads ride on. A wavy or sloped box top will spin tires, drop a load through the wood, or throw a machine off the trailer.
• Skip collision on small details: lights, chains, air lines, mudflaps, mirrors, steps if they are only visual. They cost performance and they snag vehicles.
• Do not leave the collision boxes visible (no material you care about, or put them in a collection that is not rendered). Unreal will hide them as collision.

Skeletal meshes (typical trucks and machines)

A skeletal body does not use UCX_ boxes in the same automatic way a static mesh does. After import, Unreal gives it a Physics Asset: simple bodies (boxes, capsules, spheres) parented to bones — chassis, cab, hood, each boom section, and so on. Wheels are usually handled by the vehicle wheel system, not by a fat physics body on the tire mesh.

• You still want simple shapes, one per moving part. A single giant body on the root bone will fight the wheels and the hitch.
• Keep cab and frame boxes inside the visible metal so doors and the ground do not jitter.
• You can author hint boxes in Blender for yourself, but the Physics Asset in Unreal is what the game runs. Budget time after import to check it.

FS25 boxes you already have

Keep them. An export or import script can rename a collection of FS25 collision boxes to UCX_<Mesh>_01 and so on. If you would like that script in your Blender file, ask and we can add it so you never have to rename boxes by hand.

11. Materials, textures, and LODs

Material slots

Give every material slot a stable, readable name before you export. The configurator and any hide-body-tire logic look at slot names. Good examples: M_Paint, M_Chrome, M_Glass, M_Rubber, M_Lights, M_Interior, M_Decal. Avoid Material, Material.001, and empty slots you do not use.

If a part should take the truck’s paint color, put that surface on a dedicated paintable slot. Glass, chrome, and rubber stay on their own slots so a paint job cannot tint the windshield.

UVs and textures

• Unwrap to the 0–1 UV square. Mirroring is fine. Wild overlaps that were only for Giants shaders may look wrong in Unreal.
• Use power-of-two textures (2048, 4096, …). A typical set is Base Color, Normal, Roughness, and Metalness (or a packed ORM). If you bake a normal map in Blender (OpenGL), say so — Unreal expects DirectX normals unless the material flips the green channel.
• Do not embed absolute computer paths in the FBX (an older Talbert export did this and it breaks on another machine). Keep textures in a folder next to the file, or use Relative path mode.

Motion blur

Engine motion blur is off in TERRA GENESIS. Do not rely on blur to hide a chunky tire or a sharp shadow on a wheel. Model the rim and tread so they still look all right when the truck is moving.

LODs and polycount

LODs are optional but welcome. There is no hard cap, but new models should aim lower than the heaviest converted trucks if you can (the T800 body LOD0 is about 239,000 faces — that is a lot). Practical targets:

12. Vehicles (trucks and pickups)

Driveable vehicles are usually a skeletal mesh with wheel bones, a body, opening parts, and one or more hitch empties. Copy a close existing definition (T800 for a highway tractor, 521 for a pintle / pole truck) in the New Equipment window so physics, wheels, and the vehicle class come along.

What to include

• Body at the vehicle origin, tires on the ground.
• Wheel empties WHEEL_FL, WHEEL_FR, WHEEL_R1L, … (the export script’s prefix). If you author an armature, existing project vehicles use lowercase bone names such as wheel_FL — see section 4. Doors and hood as separate bones if they open: the T800 uses Door_L, Door_R, Hood, with the pivot at the hinge.
• Hitch empties: ATTACH_FifthWheel and/or ATTACH_Pintle, ATTACH_Ball, and so on. Turn Has Fifth Wheel off in the definition when the truck truly has no plate (the 521).
• Slot empties for every place a part can go. Required slots on current semi trucks are Exhaust, Front Bumper, and Rear Bumper. If a part is still modeled into the body, mark the slot Baked until you split the mesh.
• A ROOT object at the vehicle origin, and an ENTER empty at the driver’s door.
• Light empties (sections 4 and 15).
• A Physics Asset after import, with simple bodies on the chassis and cab — not one body that covers the tires.

Pickups

Same rules, usually a ball or pintle and a SLOT_BedOrDeck. Pickup and pickup-trailer categories already exist as store tabs. Use ATTACH_Ball with RECEIVER_Coupler, or ATTACH_Pintle with RECEIVER_Lunette, as they fit. Those hitch types are being implemented; the empties should still go in.

13. Trailers

Trailers are towed. Their vehicle class must not be a driving class (Validate All will warn). A good starting copy in the editor is the Talbert RGN / low-loader definition, then change the mesh and the points.

What to include

• A clear front receiver at the real pin or ring: RECEIVER_Kingpin, RECEIVER_Lunette, RECEIVER_Coupler, RECEIVER_GooseneckCoupler, or RECEIVER_PoleReach. Do not rely on the automatic “front of the box” guess if you can help it.
• If this trailer can lead another, a rear attacher: Super B leads use RECEIVER_Kingpin plus rear ATTACH_FifthWheel; a converter dolly uses RECEIVER_Lunette plus rear ATTACH_FifthWheel.
• Separate wheel meshes and WHEEL_T1L … empties at the hubs.
• Flat, level collision on the deck and on every ramp. Ramps that fold should be their own meshes, with the pivot at the hinge (the low-loader ramp fold is a moving tool; the fold key in the current build is X).
• TIE_01, TIE_02, … along both deck edges. Put as many as the deck needs so a truck or a machine can be chained at the corners.
• Bolsters, bunks, and headboards as named meshes with their own UCX boxes if a log or a load should rest on them.

Loads on the deck

A hauled truck or machine has to ride the deck, not the ground under the trailer. That ride-along behavior is being finished in code. Your job on the model is: a flat deck collision, a ramp a vehicle can climb, and tie points. With all straps or chains done, the load will lock to the trailer; until then it can still slide on hard braking, which is intended (and there is no warning light for an unsecured load). This tie-down behavior is written, not yet tested.

14. Equipment and machines

Copy the closest existing machine definition (skidder, feller buncher, log loader, processor, excavator) so tracks or wheels, mass, and moving tools come with it. Then replace the mesh and retarget the bones or tags.

Moving parts

• House, boom, stick, head, grapple, blade, winch drum — each is a separate mesh or bone.
• The origin of that part (or the bone pivot) is the joint, not the middle of the tube.
• Rest pose should be a natural parked pose. Angle limits live on the moving-tool data (min/max degrees or translation), not in the mesh.
• Articulated machines (skidders, some loaders) also need an articulation pivot — a bone or empty at the hinge, on the centerline. The definition already has an articulation block (min/max degrees, pivot in cm, default bone name articulation).

Hydraulic cylinders

A cylinder is a barrel mesh, a rod mesh, and two anchors. The game looks at the anchors each frame and slides the rod so the visible length matches the distance (clamped to the stroke). Name them in a family, for example:

• CYL_Boom_Barrel / CYL_Boom_Rod — the two meshes
• CYL_Boom_BarrelAnchor / CYL_Boom_RodAnchor — empties (or bones) at the pins

Those become component tags or bone names on the definition (the converted T800 steering rams already follow a …_Barrel, …_Rod, …_BarrelAnchor, …_RodAnchor pattern). Put the anchors on the parts that actually move, so the ram follows the boom.

Tool attach points

If a head, bucket, or grapple can be swapped or is a separate attachment, give it a TOOL_Head (or a custom TOOL_… / ATTACH_…) at the pin. Attachments are their own equipment category and definition; the parent machine holds the matching point.

Tracks

Tracked machines use track contact points (position, radius, width, left/right) rather than wheel hubs. If you are converting from FS25, the existing pipeline can fill those from the sidecar. For a new tracked model, place contact empties along the ground path and we can wire them into the definition the same way as hubs.

15. Lights

Two different things are easy to mix up:

• Light placement empties (LIGHT_Head_L, and so on) tell the game where to put a real light (a spot or a point) and which mesh should glow. These empty names are the standard, and wiring them from Blender is Planned. Today you can still add socket names on the equipment definition’s light lists (low beam, high beam, running, tail).
• A Lights accessory slot (SLOT_Lights) is a pad where a player can install a light bar or a beacon as a part. That slot type already exists; no base truck has one yet, but a mod truck can.

Place empties at the lens, aimed the way the lamp should shine (forward for headlights, rear for tails). If you model a light bar as a swappable part, author it on a SLOT_Lights block from the ModKit, with its own small lamps parented to the part if needed.

16. Export checklist (Blender 5.2 → Unreal 5.2)

Run this in order for a new model built at real size in meters.

FBX settings (File → Export → FBX)

In Unreal, on import

• Import uniform scale 1.0. Convert Scene on. Convert Scene Unit on (meters → centimeters).
• Force Front X Axis: leave off for these standard Blender exports. (The project’s older skeletal import script turns it on, because those converted FS25 files were already X-forward in the FBX. If you use that script on a new model and the truck comes in sideways, turn it off for that file.)
• Import normals as they are if you exported custom normals. Do not generate a second set “just in case” until you have looked at the mesh.
• For static meshes, do not “auto generate” collision if you already shipped UCX boxes — you want your boxes, especially on a deck.
• For skeletal meshes, open the Physics Asset and check the bodies before you drive the machine.
• Spot-check: front of the truck is +X, roof is +Z, a known length (wheelbase, deck length) matches the real machine in centimeters.

17. Pre-flight checklists

18. Where the game data lives

The mesh is only half of a machine. The other half is an equipment definition data asset (DA_<Name>). The store, the workshop, saves, and delivery all read from it. You do not have to edit C++ to add a truck, a trailer, or a machine.

New Equipment window

In the Unreal Editor, open it in any of these ways:

• Tools → TERRA GENESIS → New Equipment…
• The + button on the main toolbar (tooltip “New Equipment”), to the right of Platforms
• Type ALS.NewEquipment in the Cmd box at the bottom of the editor

The same window also has a New Accessory tab, a Slots tab, a Hitch types list, and a Tie points (trailers) tab (that last tab is written, not compiled or tested yet). You can also run the export script and paste the JSON.

Fill the form from top to bottom: pick or copy a mesh, pick a category, pick a similar model so physics and the vehicle class are copied, then set name, price, fifth wheel, pintle, slots, and so on. Press Create. After that, use Validate All Equipment in that window (or on the Accessory tab) to check every model, slot, and part. Problems show in the window and in the log as ALS_REGISTRY problem: ….

What the definition stores (the bits that touch your model)

• Body mesh (skeletal or static), wheel set, optional fifth-wheel mesh
• Hubs (bone name, left/right, steers, radius and width in cm, position in cm)
• Fifth-wheel slide and rest position; Has Fifth Wheel; rear hitch type and location
• Mount points (slots): name, type, offset or socket, required, baked, factory part
• Tie points (cm, actor space), lights, moving tools, hydraulic cylinders, enter point
• Category, price, model tags (for example Semi, LongFrame), and the vehicle class to spawn

Mods

Outside the editor, a mod is a folder: Mods/<mod>/Vehicles/*.json and optional Parts/*.json, plus a small mod.json. The Modder Kit at ~/TerraGenesis_ModKit/ has a README, an example truck, the part catalog, and the SLOT_<Type>.fbx blocks. validate_mod.py checks the same rules as the game. Custom hitch types go in Mods/<mod>/Hitches/*.json (section 5); vehicle files use attachers and receivers. This is approved and being implemented.

A sidecar file next to a converted model (*_ue.json) is another way hubs, enter points, fifth-wheel slide, and tie points get into a definition. Units in that file are centimeters, axis X forward, Y right, Z up. Do not scale those numbers by 100 again.

19. Appendix

Renaming FS25 collision boxes

If your Blender file still has Giants-style collision boxes (often in a collision collection, named however FS25 wanted), you can keep the shapes. They need Unreal names before export:

1. Know the visible mesh name each box belongs to, exactly (for example front_bolster).
2. Rename the boxes UCX_front_bolster_01, UCX_front_bolster_02, …
3. Make sure each is a single convex hull (a cube or a convex mesh). Apply scale.
4. Export them in the same FBX as that mesh.

A small Blender script can do the rename from a collection, so your working names can stay as they are in the .blend. If you want that script dropped into your setup, say so and we will add it.

Useful project paths

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The same guide is also a 25-page US Letter PDF, last updated Nov 14, 2026.

Download the PDF