Work With QTO Sessions

import DocCallout from ‘../../../components/DocCallout.astro’;

Use a standalone viewer to inspect a file quickly. Use a project QTO session when quantities must be saved, mapped, and used in an estimate.

Choose Standalone or Project-Backed QTO

If you need to…	Use…	What Darwin keeps
Inspect an IFC, PDF, or image without creating project work	A standalone QTO viewer	Local browser cache only
Measure a drawing or map an IFC for an estimate	A project QTO session	A project-linked session, measurements, and mappings

Standalone viewers are useful for a quick first look. You can inspect a model, calibrate a drawing, take measurements, and export results. They do not save to the project or create an estimate. If a file becomes estimate-worthy, open it again from the project’s QTO Sessions area and start a project session.

Work With a Project 2D Session

Use a project 2D session for a PDF or image that needs durable takeoff.

1. Open the project’s QTO Sessions area and start or resume the 2D session.
2. In Takeoff, calibrate the scale against a known dimension for each drawing page you measure. A dimensional page (one with area, rectangle, or linear measurements) must have a positive scale calibration before the session can be reviewed.
3. Draw or edit areas, rectangles, linear measurements, counts, annotations, or auto-count results.
4. Confirm the autosave indicator reports Saved.
5. Switch to Mapping and connect measurements to the appropriate module or material.

Takeoff edits and mapping edits are saved separately. A Saving indicator means Darwin is still persisting work. An Error indicator means the latest save failed, so the unsaved edits remain only in the current browser session until saving succeeds.

Measurement types are not all equal: area, rectangle, linear, and count are real measurements that can be mapped and generated into an estimate. Annotations are on-drawing notes only — they cannot be mapped or used for quantities.

Review Agent-Driven (OpenTakeoff) Sessions

Some QTO sessions are produced by an external estimation agent rather than drawn by hand. Agent-origin sessions start as Pending Review and are not trusted until a human reviews them: Darwin refuses to generate an estimation or use their mappings in an estimate until the session is reviewed.

• The review status is derived per content revision: NotRequired, Pending, or Reviewed.
• Review the agent’s takeoff and mappings, then mark the session reviewed.
• Editing or recalibrating a reviewed agent session bumps its content revision and resets the session back to Pending — the review is about the current content, not a past pass.

Treat agent output the same way you would treat any other source: check it before it becomes an estimate.

Work With a Project IFC Session

Use a project IFC session when a 3D model needs to generate estimate quantities.

1. Start an IFC import from the project’s QTO Sessions area and upload the .ifc file.
2. Review the import session while it is In Progress.
3. Map each layer in bulk to an existing module, a new module, or a material.
4. Add an individual element override only when the layer needs an exception.
5. Generate the estimation after the mappings are ready.

An individual override changes that layer from bulk mapping to individual mapping. When generation succeeds, Darwin creates an IFC-generated estimation and marks the import session Completed.

Use Quantities in the Estimate

Project-backed mappings make quantities available in Estimation Details. Their provenance shows whether a quantity was entered manually, captured through 2D QTO, or derived from IFC. In QTO mapping, each connection is one of: map to an existing module, map to a material, create a module, or leave unmapped. The final quantity is the calibrated quantity multiplied by any multiplier applied during mapping — Darwin does not silently convert units. Review the source before approval, especially when a design file has changed or a session is agent-driven.

Next Steps

• ➡️ Map Elements to Modules
• ➡️ Build the Estimate