Coordinate Systems for Imported 3D Models

ReGame scenes use a right-handed, Y-up coordinate system. Imported glTF models are converted into that coordinate system before they are placed in a scene.

Use this guide when a model has the correct shape but appears on the wrong side of a level, faces the wrong direction, or does not align with coordinates measured in Blender.

Blender, glTF, And ReGame Space

Blender and ReGame name their axes differently:

• Blender uses X and Y across the ground plane, with Z pointing up.
• glTF uses X and Z across the ground plane, with Y pointing up.
• ReGame uses the glTF-style Y-up layout for imported 3D content and scene transforms.

For an unrotated Blender scene exported through glTF, the position basis is:

Blender (X, Y, Z) -> ReGame (X, Z, -Y)

Blender +X -> ReGame +X
Blender +Y -> ReGame -Z
Blender +Z -> ReGame +Y

The exporter also converts object rotations and hierarchy transforms. Rotation Euler values should not be copied component by component between Blender and ReGame.

GLTF And GLB Use The Same Rules

.gltf stores the glTF document as JSON with separate or embedded resource data. .glb stores the same glTF scene data in one binary file. Both formats use the same coordinate system, units, node transforms, and model-facing convention.

A coordinate difference between .gltf and .glb exports of the same scene indicates an export or import defect. It is not an expected format difference.

Position Models In ReGame Space

Place the imported model in the ReGame 3D viewport, then use its ReGame Transform3D values for scene layout. The imported hierarchy already contains the required Blender-to-glTF conversion.

For precise environment alignment:

1. Import and place the complete reference structure.
2. Select the imported wall, floor, or anchor in the ReGame scene.
3. Align new gameplay objects against the imported geometry in the ReGame viewport.
4. Use ReGame world-space bounds when code or automation needs exact placement.
5. Validate collision after the visual placement is correct.

Do not measure a Blender position and assign the same three numbers to a ReGame Transform3D. Convert the basis first, or perform the measurement after import.

Forward Direction

ReGame cameras look forward along local -Z. Oriented glTF assets use +Z as the model's front. In Blender, an authored model that faces -Y exports to the glTF +Z model-front convention.

Keep model front separate from camera forward: a character's front describes the character asset, while camera forward describes the viewing direction.

Scale And Units

glTF distances are expressed in meters. ReGame preserves the imported model data, but Auto-Scale Small Models may apply a helper scale to the generated template root. Disable that import option when the scene must retain its exact source-authored scale.

When a model has the correct orientation but the wrong size, inspect the generated template root scale before changing individual mesh nodes.

Modular Models And Building Pieces

Use Blender for mesh construction, pivots, UVs, materials, and reusable art assemblies. Use the ReGame viewport for gameplay layout, purchase pads, sensors, doors, navigation, and collision that must align with the active scene.

For a modular building kit:

• author pieces around deliberate pivots or a shared origin;
• reuse the same wall heights, wall thicknesses, floor depth, cutaway height, materials, and trim pieces when extending an existing building;
• preserve the model hierarchy when several pieces must remain aligned;
• place the imported assembly once before splitting gameplay behavior into child objects;
• keep visual pieces and their collision shapes in the same imported transform space.

Treat the existing kit as the visual contract for an expansion. Do not create a second set of generic walls and floors with approximate colors or proportions. If a missing piece is required, add it to the kit first, then assemble the new room from that shared piece in the ReGame viewport.

This avoids rebuilding an artist's coordinate conversion by hand for every wall or prop and keeps later rooms visually consistent with the original structure.

Author Fixed Expansions In The Scene

A planned room, shop wing, bridge, or other fixed level expansion should be instantiated in the scene at its final Transform3D. Keep it visible in the editor so the complete layout can be selected, measured, snapped, and checked against nearby geometry.

At runtime, a build or progression component can begin with the expansion's visual assembly and interaction branch disabled. Unlocking reveals the purchase marker; completing the purchase enables and animates the authored assembly. The progression script finds the authored object and changes its state—it does not recreate the building or own its coordinates.

Use runtime template instantiation for content whose location or quantity is genuinely dynamic, such as spawned customers, projectiles, procedural props, or repeated player-placed structures.

Troubleshooting

The model is correct but appears on the opposite side of the level.

Check whether Blender Y was copied directly into ReGame Z. Blender +Y maps to ReGame -Z for a normal glTF export.

The model faces backward after import.

Check the authored model front in Blender. For an oriented asset, Blender -Y should export as glTF +Z model front.

The model is too small or too large.

Check the Blender unit scale and the ReGame model import setting Auto-Scale Small Models. Inspect the generated template root before scaling mesh children.

The visual model aligns, but collision does not.

Confirm that collision was generated from the same imported node and follows the same Transform3D hierarchy. Reimport after changing the source model or its collision metadata.

An imported glTF hierarchy does not preserve this mapping.

Treat that as an importer defect. Record the source transform, imported Transform3D, importer options, and the smallest model that reproduces the mismatch.

The coordinate convention is defined by the glTF 2.0 specification.