Live Rendering

Open a document when a viewer must follow parameter changes or file edits. Each view subscription independently renders the document's evaluations. Exports use its committed evaluation.

Prerequisites

• Complete the Quick Start.
• Choose a transport and filesystem for the model source.

Steps

1. Open and subscribe

import { createRuntimeClient } from '@taucad/runtime/client';
import { fromMemoryFs } from '@taucad/runtime/filesystem';
import { inProcessTransport } from '@taucad/runtime/transport/in-process';
import { defineRuntime } from '@taucad/runtime/worker';
import { replicad } from '@taucad/replicad';
import { esbuild } from '@taucad/esbuild';

const runtime = defineRuntime({ plugins: [replicad(), esbuild()] });
const client = createRuntimeClient({
  transport: inProcessTransport({ runtime, fileSystem: fromMemoryFs() }),
});
const document = client.open({
  source: {
    files: {
      'main.ts':
        'import { makeBox } from "replicad"; export default ({ width = 50 }) => makeBox([0,0,0],[width,20,10]);',
    },
  },
});
const view = document.view('model');
const unsubscribe = view.on('rendered', (rendering) => {
  if (rendering.success) {
    console.log(rendering.artifact.mimeType, rendering.hash);
    // Present rendering.artifact using its MIME type.
  }
  for (const issue of rendering.issues) {
    console.warn(issue.code, issue.message);
  }
});

try {
  await view.rendering();
  await document.update({ parameters: { width: 75 } });
  await view.update({ options: { tessellation: { linearTolerance: 0.05 } } });
} finally {
  unsubscribe();
  view.close();
  document.close();
  await client.shutdown();
}

open() returns synchronously and connects lazily. Filesystem watches default to enabled. view.on('rendered') receives the settled Rendering; rendering() also reads the current projection. Keep the document and view handles for the UI's lifetime, closing them when it unmounts.

2. Separate model inputs from projection inputs

document.update({ parameters }) evaluates changed model inputs; supplied parameters replace the effective parameter bag, with model defaults resolved by the kernel. evaluateOptions belong to evaluation. view.update({ options }) changes only that projection request. Other subscriptions keep their own view, options, and instance.

document.view() follows the first offered view. For dynamic kernels, inspect evaluation.views before creating a subscription: a successful export-only evaluation may offer none. A saved declared view can become unavailable after an edit; retain its choice and expose recovery instead of silently changing it.

3. Handle supersession and failures

Both document updates and view reads/updates return a union. Check superseded before accessing evaluation or rendering. Newer work can displace older work normally; operational cancellation, timeout, and transport loss reject. Model failures resolve with success: false and structured issues. See Handle Errors.

Keep the last successful artifact visible while a replacement is pending or fails. Clear it after a successful empty result, and show unsupported MIME types without pretending they are model failures.

Variations

Create multiple document.view(id, request) subscriptions for independent panes. Instance-capable views accept a named sheet/part using instance; camera placement remains host-owned. Exports use document.export(target, request) and do not inherit the visible pane's options or transient parameter changes.

For React, useRuntime owns the document/subscription lifecycle. See Framework API.

Related

• Client API
• Render Lifecycle
• Configure Render Timeouts