What is direct editing?
Direct editing is a CAD modeling approach that modifies a model's geometry directly, without relying on the part's parametric history or feature tree. In practice it usually means editing B-rep faces and the surrounding topology through operations such as moving, offsetting, deleting, or replacing faces.
Direct editing works on the current shape of the model rather than replaying a recorded sequence of sketches and features. That makes it especially useful when the original modeling history is unavailable, which is often the case with imported parts.
How does it work?
At a geometric level, direct editing modifies selected faces and then adjusts neighboring faces so the body stays coherent. A typical face-move workflow runs through five steps:
- Detach the target face
- Move or offset it
- Extend or shrink the adjacent faces
- Trim the modified surfaces
- Stitch the result back into a valid solid
A direct edit can still be driven by numeric inputs such as distances, angles, or offsets. The difference from history-based modeling is that the edit applies to the existing geometry directly, instead of being driven by a feature-history chain.
Common direct editing operations
Typical direct editing tools work on faces and the topology around them. The table below summarizes the most common ones.
| Operation |
What it does |
Typical use |
| Move Face |
Translates, rotates, or offsets selected faces |
Repositioning or resizing a region of the model |
| Delete Face |
Removes faces while healing or capping the surrounding region |
Simplification, defeaturing, removing unwanted detail |
| Replace Face |
Trims and extends faces to a replacement surface |
Swapping geometry while keeping the body valid |
More advanced workflows combine face editing with recognized features. Some systems identify bosses, pockets, ribs, or slots, then move or modify them while rebuilding blends and maintaining tangency conditions where possible.
Direct editing vs. history-based modeling
Direct editing is not the opposite of parametric control in every sense. Both approaches can use numeric inputs; they differ mainly in how the edit reaches the geometry.
| Aspect |
Direct editing |
History-based modeling |
| What the edit acts on |
The current geometry of the model |
A recorded sequence of sketches and features |
| Needs feature history? |
No |
Yes |
| Best for |
Imported parts, local changes, design reuse |
Structured, repeatable, parameter-driven updates |
| Can use numeric inputs? |
Yes (distances, angles, offsets) |
Yes |
Applications and Industry Use Cases
Direct editing is especially valuable for imported CAD models, legacy data, and supplier geometry where the original feature tree is missing or inaccessible. It also helps with late-stage engineering changes such as adjusting fillets, resizing holes, moving pockets, simplifying a model, or making manufacturability-driven modifications without rebuilding the part from scratch.
For software developers, direct editing matters in CAD applications that support multi-CAD reuse, geometry preparation, design review with modification, simulation preprocessing, and lightweight editing of imported solids. It is often a key capability when users need to work productively on geometry that was not originally authored in the same system.
Challenges or Common Pitfalls
A common mistake is to assume direct editing is only a "push-pull" user interface. Push-pull interaction is one way to expose it, but the underlying concept is geometry editing without dependence on feature history.
Another pitfall is underestimating how much geometric healing may be required. Moving or deleting a face can force neighboring faces, blends, and tangency conditions to be rebuilt, and poor handling of these updates can produce invalid solids, broken blends, or unintended topology changes.
Direct editing is also not a complete substitute for history-based modeling in every workflow. It is excellent for local geometric changes and design reuse, but a product that needs deeply structured, repeatable, parameter-driven updates across many dependent features may still be more predictable with a feature-history approach.
How Spatial Helps
Spatial's modeling kernels handle direct editing directly, so applications can edit geometry rather than just display it.
The 3D ACIS Modeler supports both history-free direct modeling applications and history-based feature-tree workflows. Its modification toolkit includes Direct Editing alongside Boolean, blending, thickening, and offsetting operations, and it manipulates local areas of a model while managing the surrounding topology so the body stays valid after an edit.
CGM Modeler combines direct editing with feature recognition. It identifies features such as holes, pads, and fillets on imported models without accessing the feature tree, then edits them, for example changing a hole's diameter and shape while keeping the surrounding fillets and other features intact.