Reference

Glossary

Definitions of the CAD and geometry terms behind QuantCAD, and of the words you'll see across the app and these docs.

Last updated Sep 27, 2026

CAD and geometry

B-rep (boundary representation): A way of storing a 3D solid by its exact bounding surfaces (planes, cylinders, freeform patches) together with the topology that connects them: which faces meet along which edges, and which side is solid material. QuantCAD builds every part as a B-rep solid.
Mesh: A surface made of flat triangles that approximate a shape. Good for display and 3D printing, but it holds no exact faces, edges or dimensions.
Tessellation: Turning exact surfaces into triangles for display or STL export. A B-rep solid can be tessellated at any resolution; turning a mesh back into exact surfaces is hard.
NURBS: Non-uniform rational B-splines, the mathematical surfaces CAD uses for freeform shapes. A B-rep solid stores them exactly.
Solid: A closed set of faces that encloses a volume. A B-rep solid is only valid when its faces close into a watertight shell.
Topology: The connections between the faces, edges and vertices of a solid.
Watertight: A shell or mesh with no gaps, so it encloses a volume. Slicers need watertight meshes to print.
Geometry kernel: The software library that creates and edits solid geometry and computes operations such as booleans, fillets and offsets. QuantCAD uses Open CASCADE.
Open CASCADE: The geometry kernel QuantCAD builds its B-rep solids on, also known as Open CASCADE Technology (OCCT).
STEP: ISO 10303, the neutral file format CAD systems use to exchange B-rep solids with their surfaces and topology. QuantCAD writes STEP AP242 in millimetres. See File Formats.
AP242: The STEP application protocol for managed model-based 3D engineering (ISO 10303-242), used to exchange 3D CAD models between systems.
STL: A file format that stores a triangle mesh and nothing else, not even units. Slicers use it for 3D printing. QuantCAD generates STL from the solid in Draft, Normal or High quality.
Fillet: A rounded transition between two faces, defined by a radius.
Chamfer: A flat, angled cut that replaces a sharp edge.
Tolerance: The allowed variation from a nominal dimension, such as 10 mm ± 0.1 mm.
Parametric model: A model defined by dimensions and relationships, so changing a value updates the geometry.
Text-to-CAD: Using AI to turn a written description into a CAD model: a solid with exact faces, edges and dimensions, rather than a mesh. See What is text-to-CAD?.
Text-to-mesh (text-to-3D): Using AI to turn a description into a triangle mesh, usually for renders, games or concept visuals. See Text-to-CAD vs text-to-mesh.

Core product terms

Product: A QuantCAD design: the container for your prompts, revisions and exports. Created from New Product.
Prompt: A natural-language instruction you send in the chat. Either a Build or an Ask.
Build mode: A prompt mode that modifies geometry. Each Build creates a new revision. See Build vs Ask.
Ask mode: A prompt mode that asks a question without modifying the model. See Ask Mode.
Run: A single execution of a Build or Ask prompt. The chat shows status while a run is in progress.

Credits & billing

Credit: The unit of usage in QuantCAD. Reserved at the start of a run and captured when the run completes.
Plan credits: Monthly subscription credits from your active plan. They roll over up to a tier-specific bank limit. See Credits & Plans.
Bonus credits: Credits that never expire, from the signup bonus, refill purchases, referrals or feedback rewards. Spent after plan credits.
Bank limit: The maximum balance of plan credits that can roll over. Limits are set per tier and are larger on higher tiers. Once reached, additional plan credits aren't added until you spend some.
Daily drip: An onboarding bonus of 5 credits per day, capped at 25/month, granted for the first 2 months on any plan.
Refill pack: A one-time credit purchase for Pro/Business subscribers. See Billing.
Reservation / hold: Credits temporarily set aside for a run that's about to start. Released back if the run is cancelled.
Stripe Customer Portal: The secure portal where you change your plan, update payment methods, and download invoices. Opened from the in-app Billing page.

Workspace & viewer

Workspace: The product page combining the chat, the 3D viewer and the project header. See Workspace Overview.
Project header: The slim top bar of the workspace. Hosts search, versions, lifecycle, downloads, settings and help. See Project Header.
Action Bar: The viewer toolbar with select, hide, measurements, clipping and downloads. See Action Bar.
Clipping plane: An invisible plane that hides everything on one side of it, letting you look inside the model without modifying geometry.
Projection: Perspective (with depth) or Orthographic (no foreshortening). Toggle in the Action Bar.
Z-up: QuantCAD's coordinate convention: the Z axis points up. Matches Fusion 360, SolidWorks and most CAD tools.

Lifecycle & history

Revision: A snapshot of geometry created by a Build prompt. Browse and switch them in the Versions menu. See Versions & Revisions.
Full Revision: A fork: duplicates the current revision into a brand-new product. See Full Revision.
Lifecycle: The high-level stage of a product: Draft, Prototype In Work, In Review, Released or Obsolete. See Product Lifecycle.
In Review lock: Products in the In Review stage are locked from edits until moved back to Prototype In Work.
Lineage: The chronological history of all revisions of a product, shown on the Traceability page. See Traceability.