Roblox Asset Pipeline and UGC

Target: Roblox Studio (October 2026 build) on macOS, driven through the scenario-roblox-expert toolkit.

Expert level here means every mesh arrives in Studio already at its size in studs, facing -Z, under its triangle budget, closed when it must be, with maps sized and split for Roblox, and with numbers that prove it. Fix in Blender, preview and audit in Studio without uploading, validate locally to green, and stop exactly where Roblox needs an uploaded asset.

If a sibling skill named here is missing from your available skills, ask the user to install it (npx skills add scenario-labs/skills --skill <name>); unattended, proceed from tool schemas and flag the gap.

REQUIRED BACKGROUND: scenario-roblox-expert (channels, review loop, toolkit, current-Roblox traps).

Stance (the expert delta)

1. Treat an AI GLB as raw input with known defects. Image-to-3D output arrives about 0.95 units across, front facing +Z, every material doubleSided, metallicFactor 1.0 with painted partial metalness, 2048 px JPEG maps and pinholes [added, measured on two generator outputs]. Raw meshes need remesh, pivot and scale work (CallMeDogey).
2. Decide size in studs in Blender, not in Studio. One Blender unit is one stud; glTF then needs no Importer scale (Creator Docs, Importer; KatsBits [00:02:56]). Props pivot at the bottom center (Common Sense Machines [00:02:39]); accessories at the mesh center (validation #173).
3. Turn the front to -Z before export. glTF fronts face +Z; Roblox's LookVector is -Z. A 180 degree yaw in Blender fixes it for good [added].
4. An accessory is its bounding box, and a hat is its crown. Bounds are per AccessoryType, measured around the attachment, and rotation grows the box (KatsBits [00:10:34]). The box follows AvatarPartScaleType: none or Classic gives the GetValidationRules() box (Hat 3 x 4 x 3), ProportionsNormal the docs row (1.87 x 2.5 x 1.87) [added, live]. Scale a hat so its crown clears the head, then check the box: filled to the Normal box by its brim, the test hat's crown was narrower than the default head [added].
5. Measure watertightness; do not trust a fill operator. bmesh.ops.holes_fill capped 2 of 9 pinholes on the test hat, and decimation then created edges with three faces [added]. Cap each loop, repair after decimation, count boundary edges again. Never use Make Double Sided to hide holes (Creator Docs, Importer).
6. Preview without uploading. EditableMesh plus EditableImage rebuild the prepared mesh and its PBR maps in the place for audits, wear tests and captures [added]. That content is session-only and empty in a playtest copy [added]; ship through the Importer with Upload to Roblox off while iterating (Creator Docs; Templates [00:02:31]).
7. Validate locally to green, then stop. ValidateUGCAccessoryAsync runs Roblox's validator inside a playtest. Fix every string about geometry, schema, materials or bounds; ownership and moderation strings need an uploaded asset and end the agent's part (Creator Docs, validation system).
8. Textures follow density, not the source. 256 px per 2 x 2 x 2 studs, power of two; OpenGL normals; metalness 0 or 1 unless satin by design; opaque ColorMap on accessories (Creator Docs, texture specifications and SurfaceAppearance).

Establish first

• Destination: in-experience prop, or Marketplace avatar item. Only the second must pass validation and be watertight.
• Size in studs per asset (an R15 character is about 5 to 6 studs tall), and for accessories the AccessoryType and the AvatarPartScaleType it will declare (Classic, ProportionsNormal, ProportionsSlender).
• Budget class: hero prop, clutter, or accessory (4,000 triangles).
• Source: GLB from scenario-3d (preferred), FBX (needs FBX Unit Scale), or OBJ (mesh only).
• Rigged or skinned input goes to scenario-roblox-animation after import.
• Defaults when unanswered: prop, bottom pivot, longest side from the concept's scale, texture side from texture_side, hat crown opening 1.35 studs, no scale type (Classic box).

Procedure

Full code and recorded results: procedures.md. Setup: import rbx_assets as ra (it finds the lead toolkit). Every snippet ran in Studio 0.743 or Blender 5.2 on 2026-10-19, except those marked not yet run; Edit and playtest captures confirmed the fit (a covered window returns dark frames: judge on numbers then).

1. Triage. Goal: know the defects. How: ra.glb_info(path) offline. GATE: triangles, size, map sizes, doubleSided, skins and extensions written down per asset.
2. Fix in Blender. Goal: size, facing, pivot, budget, closed mesh, Roblox maps. How: ra.blender_prep({**ra.PROP_PREP or ra.ACCESSORY_PREP, "input", "out_dir", "yaw": 180, "scale": ...}), with {"opening": 1.35, "band": [0.08, 0.2], "cap": [3, 4, 3]} for hats; it waits for the machine guard, runs blender -b, writes a report and four Workbench views. GATE: ra.gates(report["after"], kind, type) all pass, and the front view shows the front.
3. Read live rules. Goal: today's limits. How: ra.run(studio, "return AssetAudit.rules()", kit=["AssetAudit"]). GATE: AccessoryMaxTriangles, MaxTextureSize and the type's attachment Size and Offset recorded; the offline gates use them.
4. Preview and audit in Studio. Goal: the asset in the place, measured. How: ra.stage the packed mesh and maps, then MeshBuild.build and AssetAudit.prop. GATE: Size equals the Blender size within 0.01 stud, the triangle count matches, no audit error, the front capture shows the front.
5. Build the accessory. Goal: Accessory, Handle, one attachment named for the type. How: MeshBuild.accessory, then AssetAudit.accessory(acc, rules). GATE: zero errors; AvatarPartScaleType is the only warning (the Accessory Fitting Tool adds it).
6. Wear test. Goal: it sits right. How: UGCCheck.rig and UGCCheck.wear in Edit, then captures front and side. GATE: a joint exists, attachment error under 0.01 stud, opening.clears (crown at least head-wide at the head top), and the brim rests on the head in the captures.
7. Validate locally. Goal: only upload-bound strings left. How: in a Playtest, ra.stage(..., dm="Server") and UGCCheck.validate(acc, Enum.AccessoryType.Hat); run single-fault copies as negative controls, at most 10 calls per 60 seconds. GATE: the item returns valid with no string; every fault copy fails.
8. Hand off the import. Goal: the shipping path. How: the human or a computer-use agent imports <name>_roblox.glb with the settings in gui-paths.md; the Accessory Fitting Tool generates the final accessory. GATE: the imported MeshPart's Size equals the preview's; P7 audits it again.

Numbers

Value	Relative to	Source
20,000 triangles	One mesh in a place	Creator Docs
4,000 triangles	Rigid or layered accessory	Creator Docs; live AccessoryMaxTriangles
60,000 vertices, 20,000 triangles	One EditableMesh; a quad counts as 2	EditableMesh reference
256 px per 2 x 2 x 2 studs	Texture side, next power of two	Texture specifications
4096 px	Place textures (since 2026-01-30)	DevForum
1024 px	Avatar ColorMap, live MaxTextureSize; other avatar maps 256	Validation system; live
1024 px	EditableImage side	AssetService reference
Hat 3 x 4 x 3 studs	No AvatarPartScaleType or Classic; ProportionsNormal 1.87 x 2.5 x 1.87	Live rules and validator; accessory specifications
10 pieces	Disconnected components per accessory MeshPart	Validation #187
0.05 to 4.0 studs	Per-axis MeshPart size for avatar parts	Validation #176, #177
0.02	Lowest MeshPart.Transparency for soft alpha with AlphaMode Transparency	SurfaceAppearance
0 to 40	EmissiveStrength on Marketplace items	SurfaceAppearance
1.35 studs	Hat crown opening, for a 1.16-stud default R15 head	[added, wear test]
0.3 stud	Hat attachment above the mesh bottom: brim a quarter of the head height below its top	[added, wear test and fit render]
10 calls per 60 s	ValidateUGCAccessoryAsync rate limit	Live error string

Quality gates

Measurable:

• Blender report: every ra.gates entry passes; the raw input fails what it should (negative control).
• Studio: AssetAudit returns no error; Size and triangle count equal the report.
• Wear: joint present, attachment error under 0.01 stud.
• Validator: no string left that is fixable without an upload.

Visual (one contact sheet, 1,600 px at most, opened and read):

• Front of each asset faces the camera from -Z; props stand on the ground; nothing black or inside out.
• The hat sits on the head from the front and the side, neither floating nor sunk past the brim.
• Textures read like the concept: details in place, no smeared atlas.

Score the result with critique.md before calling it done.

Common mistakes

Mistake	Symptom	Fix
Importing the unit-sized GLB as is	Prop the size of a brick	Scale in Blender to studs; Scale Unit Studs
No yaw on glTF input	Lock or face on the back side	yaw: 180 before export
Make Double Sided to hide holes	Validation boundary-edge error; double triangles	Close holes in Blender
Trusting holes_fill	"Not watertight" after the fix	Cap loops, repair after decimation, recount
Decimating in Studio's head	Over 4,000 triangles at upload	Decimate in Blender to 3,800
Packed metallic-roughness used as one map	Metal everywhere or nowhere	Split G and B to grayscale maps
Partial metalness kept	Tinted, plastic-looking metal	Snap to 0 or 1 after reading the mask
ColorMap with alpha on an accessory	Validation #145, see-through spots	opaque_color
TextureID and SurfaceAppearance both set	Validation #146	One of them
Attributes or tags left on the accessory	Validation #191	Strip before validating
Pivot at the feet for an accessory	"Mesh data is not centered"	Center pivot
Rotating the hat inside the fitting box	Box red although the mesh looks inside	Re-center and orient in Blender
Sizing a hat by its brim	Head pokes through the crown	scale.opening, then opening.clears
Massless true on the Handle	Validator: "Expected to be = false"	Leave the default
AddAccessory from the client on your own character	No joint; the hat falls	Attach on the server; seat a local preview by CFrame
Hat mesh and texture built from Editable content on the server	Clients draw a small checkered cube at the Handle	Keep the joint on the server; on each client, apply a locally built mesh (ApplyMesh) and SurfaceAppearance (procedures P8)
Expecting an EditableMesh preview to save	Part empty after reopening	Session only; import for real
Expecting the Edit preview in a playtest	Copied parts keep Size but have no mesh	Stage and build in that data model

Handoffs

• Receives from scenario-3d: GLB or FBX meshes with PBR maps (image-to-3D, remesh, retexture, rigging). Ask for a remesh run when decimation damages the silhouette.
• Receives from scenario-textures: PBR sets for one mesh, which become SurfaceAppearance here. Tileable sets go to scenario-roblox-environment as MaterialVariants.
• Receives from scenario-game-assets: the concept image that scenario-3d turns into a mesh (one centered subject, plain background, front view). Icons, sprites and UI art go to scenario-roblox-ui, decals to scenario-roblox-environment.
• Delivers to scenario-roblox-environment: MeshParts at true size with a bottom pivot, a proposed CollisionFidelity and the gate report; it places, sets final fidelity and LevelOfDetail, and lights.
• Delivers to scenario-roblox-animation: rigged or skinned imports, checked for scale and facing.
• Delivers to scenario-roblox-performance: each import batch, for its memory and batching audit (references/memory-and-crowds.md, PerfAudit.assets), which this skill does not repeat.

Current Roblox notes

• EditableMesh and EditableImage are not creatable with Instance.new; use AssetService:CreateEditableMesh(), CreateEditableImage() and Content.fromObject. Published experiences need the Mesh and Image APIs setting.
• CreateSurfaceAppearanceAsync takes EditableImage content only; maps cannot be swapped afterward.
• The Avatar Joint Upgrade joins rigid accessories with RigidConstraint, not a weld. Find attachments with FindFirstChild(name, true).
• GenerateMeshAsync is scheduled for deprecation; GenerationService:GenerateModelAsync with schema Car5 or Body1 replaces it.
• Places take 4096 px textures since 2026-01-30; avatar limits come from GetValidationRules().
• Studio MCP runs with plugin rights: in Edit it wrote SurfaceAppearance.ColorMap, ColorMapContent and MeshPart.CollisionFidelity without error. Game scripts have fewer rights; test a snippet in a Script before shipping it in one.
• generate_mesh (Studio MCP) returns only {generationName, tag} and inserts a Model of segmented MeshParts with asset IDs and a TextureID; pass size, maxTriangles and segmentation.

References

• references/expert-notes.md: principles by source, disagreements, and what the live runs added.
• references/procedures.md: full code for P1 to P11 with test ids and results.
• references/avatar-item-checks.md: engine calls behind each wrapper, motion on several bodies, six-view opacity, tilt, Fitting Tool leftovers (Unknown type, TexturePack, MeshSize).
• references/critique.md: blocking and quality checks for your own output.
• references/gui-paths.md: Importer, Accessory Fitting Tool, validation plugin and Blender paths.
• references/sources.md: every doc and video with credentials and timestamps.
• scripts/rbx_assets.py: GLB triage, Blender runner with the machine guard, gates, texture sizing, payloads, kit runner.
• scripts/blender_roblox_prep.py: the headless Blender inspect and prep pass.
• scripts/agentkit/assets/: Payload, MeshBuild, AssetAudit, UGCCheck.