asset-pipeline

Original：🇺🇸 English

Translated

Turn generated or hand-made art into exactly what a game engine loads. Covers sprite cutout, trim and nearest-neighbour fitting to frame sizes, pixelation to a palette, sprite sheets and strips, player/team-colour masks, seamless textures, and rendering a 3D model into sprite frames from the game's own camera (isometric/RTS 8 or 16 headings, side view, top-down) with Blender. Use after generating assets, or when the user asks to make sprites, sprite sheets, animation frames, isometric unit sprites or icons for a game.

4installs

Sourcerehan-remade/universal-modder

Added on2026-10-01

NPX Install

npx skill4agent add rehan-remade/universal-modder asset-pipeline

SKILL.md Content

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Asset pipeline: from art to engine-ready files

The fal-assets skill makes pictures. This skill makes files the game accepts: the right size, frame layout, orientation, alpha, palette and format. All commands are

um sprite ...

and

um render3d ...

; each has

--help

with examples.

1. Learn the target format from the game itself

Before converting anything, open two or three of the game's own assets and write down in MODLOG.md:

Dimensions: frame size, frames per sheet, and the layout (vertical strip / grid / one file per frame).
Orientation: which way the art faces (Terraria: items point right, NPCs face left, the engine flips them), and where the pivot or hotspot sits (AoE2: the unit's ground point at the canvas centre).
Alpha: hard 1-bit edges (BC1 punch-through, pixel art) or soft.
Style: palette size and outline (dark 1-2 px outline in most pixel-art games).
Format: PNG, DDS BC1/BC3/BC7, XNB, SLD, atlas + JSON...

The draw code is the final authority. In Terraria, NPC frame height = texture height /

Main.npcFrameCount

, so any consistent frame size works.

2. 2D pipeline

bash

um sprite info raw.png                                    # size, alpha coverage, corner colour
um sprite cutout raw.png cut.png                          # flat bg → transparent (border flood fill keeps interior whites)
um sprite cutout raw.png cut.png --grey 150 --keep-top 0.8   # also remove a soft grey shadow / the floor under it
um sprite fit cut.png item.png --size 64x26 --hard-alpha  # trim + ONE nearest-neighbour scale into the frame
um sprite fit cut.png npc.png --size 38x34 --anchor bottom   # standing sprites sit on the frame's bottom edge
um sprite pixelate cut.png px.png --size 32x32 --colors 16 --outline   # true pixel art from painterly art
um sprite palette px.png px2.png --from stock_sprite.png  # snap to the game's own colours
um sprite frames npc.png frames/ --n 3 --kind bob          # cheap idle animation (bob/squash/wobble/flash)
um sprite sheet sheet.png frames/*.png --vertical         # Terraria-style strip (or --cols N grid)
um sprite slice sheet.png out/ --frame 32x32              # the other direction
um sprite team-mask unit.png unit_grey.png --hue blue     # player-colour mask (+ desaturated sprite)
um sprite preview item.png look.png --scale 6             # checkerboard + zoom: LOOK at it before shipping

Pixel art: scale once, with nearest neighbour, to the final size. Never scale pixel art twice.
Painted / HD art: use
```
fit --smooth
```
.
Real frames: for animation frames beyond bob/squash, generate each frame with the fal edit endpoint using the base sprite as reference ("same drone, rotors tilted, frame 2 of 4"), then cut out and fit each frame the same way. Or go 3D (below).

3. 3D → sprites (consistent angles and animations)

bash

um fal model3d concept.png --name unit                   # textured GLB (Trellis 2 by default)
um render3d assets/gen/unit.glb frames/ --preset aoe2 --length 80 --forward-yaw -90 \
  --anims idle:10:bob,walk:12:walk,attack:16:lunge,death:20:die --shadows --samples 40
um render3d assets/gen/unit.glb side/ --preset side --canvas 128 --length 110 --engine eevee   # platformer facing R + L

Presets:

Preset	Projection	Camera	Facings
`aoe2`	ortho	30°	16 clockwise from east
`iso8`	ortho	30°	8
`trueiso`	ortho	35.264°	8
`topdown`	ortho	—	8
`side`	ortho	—	2 (right, left)
`turntable`	persp	—	24 (promo/icon spins)

```
--length
```
sets the model's longest horizontal side in pixels at 1x, so match stock units.
```
--forward-yaw
```
turns the model so its nose faces +X; check the first frame.
```
--shadows
```
adds a shadow-only pass (
```
*_s.png
```
) for engines that keep shadows in their own layer.
Motions: bob, walk, lunge, die, wreck, spin.
Then pack with
```
um sprite sheet
```
, or with an engine writer (e.g.
```
examples/aoe2-de-civ/sld.py
```
).
Needs Blender (
```
blender
```
on PATH or
```
BLENDER=...
```
). Cycles uses the GPU when available.
Dark generated textures: raise
```
--sun
```
/
```
--ambient
```
, or brighten in post.
For game-ready 3D (not sprites), remesh with
```
um fal run tripo3d/tripo/remesh mesh_url=@unit.glb face_limit:=8000
```
, then convert in Blender (GLB → FBX/OBJ) with the engine's scale and axis convention: Unity Y-up metres, Unreal Z-up centimetres, Bethesda NIF via PyNifly.

4. Textures and materials

Tiling:
```
um fal texture
```
generates it tiled. Check with
```
um sprite tile-preview t.png t3.png
```
. Fix seams on other images with
```
um sprite seamless
```
.
PBR sets:
```
um fal pbr
```
. Convert to the engine's packing: Unreal ORM (occlusion/roughness/metal in RGB), Unity metallic-smoothness (smoothness = 1 - roughness in alpha).
DDS: texconv (DirectXTex) or
```
magick
```
with DXT settings. BC7 for quality, BC1 for cutout sprites, BC3 when alpha is soft.

5. Verify in the game

Put one converted asset into the game and screenshot it next to stock art (

um win shot

). Check the scale, facing, pivot, outline and palette. Fix the recipe, then batch-convert the rest with the same commands (a small script or Makefile, so the pipeline is reproducible from

assets/gen/

).