MotionForge

MotionForge turns a declarative JSON document into rendered motion graphics. There is no timeline UI and no node editor — the document is the source of truth, which makes compositions diffable, reviewable, and generatable by a program or an agent.

The project began with a deliberate core reset, and that reset is still the design discipline: a feature lands only when it fits cleanly into the staged pipeline. Nothing gets bolted on sideways.

The pipeline

JSON document
  -> mf-parser      read source-shaped JSON into raw schema data
  -> mf-compiler    validate, normalize, expand generators, resolve references,
                    build the dependency graph, prepare typed property sources
  -> mf-eval        compute one concrete frame from frame-native context
  -> mf-layout      Taffy-backed block/flex plus absolute positioning
  -> mf-transform   anchor, position, scale, rotation, skew, perspective
  -> mf-resolver    convert to renderer-ready scene data
  -> mf-render-vello
  -> PNG / frame sequence / MP4 / transparent WebM + MOV

Each stage has a contract, and the contracts are the point. The renderer consumes resolved scene data only — it cannot reach back for the document, which is what keeps it swappable. Evaluation is frame-native, so any frame can be computed independently without simulating the ones before it.

What it renders today

• Variables, layers, children, and style/transform/property namespaces.
• Frame-native context: $frame, $time, $fps, $duration, $progress.
• References, numeric expressions, keyframes, easing, and dependency-cycle detection.
• Vector nodes — rect, ellipse, line, polygon, star, path — plus .svg import that expands into native vector paths, so imported artwork animates and takes effects like anything else.
• group nodes with hierarchy, clipping, opacity, grouped effects, and blend modes.
• Text, image, video, and shader render providers. Video supports constant-rate playback_rate and an animatable time_remap curve for speed ramps, freeze frames, and reverse.
• audio timeline nodes with trim, volume, and pan, muxed into MP4.
• Reusable prefab definitions with child time scopes and time remapping.
• Vector masks — clip and alpha mattes — with invert, feathering, and reveal presets.
• Scene transition nodes: fade, slide, wipe, iris, radial, and zoom.
• Linear, radial, and conic gradient paints.

Assets resolve from local paths, http(s), or data: URIs — images, video, audio, fonts, and .cube LUTs — fetched and decoded once, then cached. Remote fetching goes through an injectable AssetFetcher so the library has no opinion about networking.