witySceneRender — Render Gateway

witySceneRender is the single public entry point for all wity-scene rendering. Send a scene XML document and an optional output format — the gateway parses the scene, selects the correct internal pipeline, and returns the rendered output URL. Callers never invoke the downstream Lambdas directly.

Location: services/scene-render/gateway/

---

Input

{
  "sceneXml":      "<wity-scene>...</wity-scene>",
  "outputFormat":  "mp4",
  "options": {}
}

Field	Type	Default	Description
sceneXml	string	required	The <wity-scene> XML document
outputFormat	string	"mp4"	Output format: "mp4", "pdf", "pptx"

"mp4" options:

Option	Type	Default	Description
options.fps	number	30	Output frame rate
options.sceneWidth	number	1280	Canvas width px
options.sceneHeight	number	720	Canvas height px
options.fontManifest	object	{}	Custom fonts: { "FontName": "https://url/font.ttf" }

"pdf" options:

Option	Type	Default	Description
options.ts	number	0	Scene time (seconds) to snapshot
options.timestamps	number[]	—	One page per timestamp; overrides ts
options.variant	"standard" | "print"	"standard"	Screen (96 DPI) or print-ready (300 DPI)
options.dpi	number	96 / 300	Override render DPI
options.fontManifest	object	{}	Custom fonts

"pptx" options:

Option	Type	Default	Description
options.ts	number	0	Scene time (seconds) to snapshot
options.timestamps	number[]	—	One slide per timestamp; overrides ts
options.fontManifest	object	{}	Custom fonts

---

Output

{ "url": "https://...", "fileSize": 9876543, "pipeline": ["witySceneToVideo", "witySceneCompose"] }

Field	Type	Description
url	string	Public S3 URL of the rendered output
fileSize	number	Output file size in bytes
pipeline	string[]	Which internal Lambdas were invoked (observability / cost attribution)
pages	number	Number of pages — "pdf" only
slides	number	Number of slides — "pptx" only

---

Routing

"mp4" — content-aware routing

The gateway parses the scene and inspects element tags across all layers:

Scene content	Route	pipeline value
Only ws-rect / ws-text / ws-image	witySceneToVideo only	["witySceneToVideo"]
Graphics + ws-video / ws-audio	witySceneToVideo → witySceneCompose	["witySceneToVideo", "witySceneCompose"]
Only ws-video / ws-audio	witySceneCompose only (graphicsMp4Url: null)	["witySceneCompose"]

caller → witySceneRender
              │ parse + detect content
              ├─ hasGraphics? → witySceneToVideo → graphicsMp4Url
              └─ hasMedia?    → witySceneCompose(graphicsMp4Url) → final URL → caller

"pdf" and "pptx" — single downstream call

No content inspection. ws-video and ws-audio are silently skipped by the snapshot renderer.

caller → witySceneRender
              ├─ "pdf"  → witySceneToPdf  → S3 URL → caller
              └─ "pptx" → witySceneToPptx → S3 URL → caller

---

Lambda config

Setting	Value
Function name	witySceneRender
Runtime	Node.js 20
Memory	512 MB
Timeout	660 s (11 min — accommodates two sequential 300 s downstream calls for mp4)
Ephemeral storage	512 MB
FFmpeg layer	Not required — this Lambda only parses and routes

---

Environment variables

Variable	Default	Description
SCENE_TO_VIDEO_FUNCTION	witySceneToVideo	Graphics compiler Lambda
SCENE_COMPOSE_FUNCTION	witySceneCompose	Full compositor Lambda
SCENE_TO_PDF_FUNCTION	witySceneToPdf	PDF renderer Lambda
SCENE_TO_PPTX_FUNCTION	witySceneToPptx	PPTX renderer Lambda
AWS_REGION	ap-south-1	AWS region for Lambda invocations

IAM note: The execution role must have lambda:InvokeFunction on all four downstream Lambdas.

---

Error responses

Status	Condition
400	sceneXml missing
400	Invalid JSON body
400	Malformed XML (parse error)
400	Unknown outputFormat
400	Scene has no renderable elements (mp4 only)
500	Downstream Lambda failed

---

Downstream Lambdas (internal — do not invoke directly)

witySceneToVideo — graphics compiler

Renders ws-rect, ws-text, ws-image → PNG frame sequence → silent MP4. ws-video and ws-audio are silently ignored.

Package: @wity/scene-to-video

Setting	Value
Memory	3008 MB · Timeout 300 s · Ephemeral 4096 MB
FFmpeg layer	arn:aws:lambda:ap-south-1:175033217214:layer:ffmpeg:1

witySceneCompose — full compositor

Blends ws-video clips + ws-audio tracks + optional graphics overlay via FFmpeg filter_complex.

Package: @wity/scene-compose

Setting	Value
Memory	2048 MB · Timeout 300 s · Ephemeral 4096 MB
FFmpeg layer	arn:aws:lambda:ap-south-1:175033217214:layer:ffmpeg:1

witySceneToPdf — PDF renderer

Snapshots scene at one or more timestamps via node-canvas → pdf-lib → PDF file.

Package: @wity/scene-to-pdf

Setting	Value
Memory	2048 MB · Timeout 120 s · Ephemeral 1024 MB
FFmpeg layer	Not required

witySceneToPptx — PPTX renderer

Snapshots scene at one or more timestamps via node-canvas → pptxgenjs → PowerPoint file.

Package: @wity/scene-to-pptx

Setting	Value
Memory	1024 MB · Timeout 120 s · Ephemeral 1024 MB
FFmpeg layer	Not required

---

S3 output

The gateway does not write to S3. Downstream Lambdas write to the wity-user-generated-content bucket:

Lambda	Prefix
witySceneToVideo	scene-compiled/
witySceneCompose	scene-composed/
witySceneToPdf	scene-pdf/
witySceneToPptx	scene-pptx/

---

Extensibility

The gateway uses a PIPELINE_REGISTRY keyed by outputFormat. Adding a new format:

1. Deploy a new specialized Lambda.
2. Add one entry to PIPELINE_REGISTRY in handler.js.
3. Add the corresponding env var to the gateway config.

No changes to any existing Lambda.

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Related

• Deployment guide — full server-side pipeline walkthrough
• @wity/scene-to-video — graphics compiler package
• @wity/scene-compose — full compositor package
• @wity/scene-to-pdf — PDF renderer package
• @wity/scene-to-pptx — PPTX renderer package