CGR File Format

Technical Explanation

What Is a CGR File?

A CGR file stores the graphical representation of a CATIA V5 model. It is not the same as a full CATPart or CATProduct file because it does not contain the complete editable CAD definition of the model.

Instead, CGR stores a tessellated approximation of the model’s visible geometry. In practical terms, the model is represented as a set of flat triangular facets rather than exact B-Rep surfaces, analytic edges, or NURBS geometry.

This makes CGR useful when users need to view, load, review, or share a CATIA model without opening the full design data. It is especially important in large assembly workflows where loading every exact part model would be slow or unnecessary.

What CGR Stores

A CGR file typically stores the information required to display a model efficiently. This may include tessellated geometry, visual attributes, and limited structure or annotation data depending on how the file was created and used.

Common CGR data includes:

The key point is that CGR is a visualization representation. It is optimized for display and review, not for full design editing.

What CGR Does Not Store

A standalone CGR file does not contain the same information as a native CATIA design file. It generally does not preserve:

• Exact B-Rep geometry
• NURBS surfaces or precise analytic edges
• Parametric feature history
• The construction tree
• Editable constraints
• Full design intent
• Complete manufacturing metadata
• Complete assembly relationships across multiple specification-tree levels

This distinction matters because a CGR file may look visually accurate while still being unsuitable for workflows that require exact geometry, such as machining, detailed simulation, or feature-level editing.

CGR, Tessellation, and B-Rep

CGR geometry is tessellated. Tessellation converts smooth CAD geometry into a mesh made of triangles. The smaller and denser the triangles, the closer the visual approximation can appear to the original model.

However, tessellation does not preserve exact geometry. A cylindrical face in a CATPart file may be mathematically defined as a true cylinder, while the same face in CGR is represented by many flat facets that approximate the cylinder’s appearance.

This difference is important for downstream workflows. A CGR representation may be suitable for display, digital mock-up, or approximate inspection, but it should not be treated as equivalent to exact B-Rep geometry.

Visualization Mode vs. Design Mode in CATIA V5

CGR is closely related to CATIA V5 visualization workflows. In Visualization Mode, CATIA can display components using their lightweight CGR representation. In Design Mode, the system loads the full design data required for editing and exact geometry operations.

When a large assembly is opened, components that are not being edited can be displayed from CGR cache data. This reduces memory usage and improves load performance because the application does not need to load every full CATPart or CATProduct definition immediately.

The trade-off is clear: Visualization Mode improves performance, while Design Mode provides access to the complete editable CAD model.

Part-Level CGR vs. Assembly-Level CGR

CGR can be used at different levels of a CATIA V5 workflow.

Assembly-level CGR is useful for performance, but it should not be confused with a complete CATProduct structure. It may not preserve all levels of the CATIA specification tree or all design information associated with the original assembly.

CGR vs. CATPart vs. CATProduct

CGR is often used alongside CATPart and CATProduct files, but the three formats serve different purposes.

A CATPart or CATProduct file may contain both exact geometry and cached visualization data. A standalone CGR file, however, should be treated as tessellated geometry only.

Applications and Industry Use Cases

CGR files are useful in engineering environments where teams need fast access to CATIA V5 geometry without loading the full editable model.

In design review, CGR enables users to inspect the external shape of parts and assemblies, navigate complex models, and perform lightweight visual checks. It can support approximate measurement, sectioning, and interference screening, but exact validation should rely on the native CAD model or another exact geometry representation.

In large assembly management, CGR helps reduce the cost of opening and navigating complex products. Aerospace, automotive, heavy equipment, and industrial machinery assemblies may contain thousands of parts, and loading all exact B-Rep data at once can be unnecessary for review tasks.

In digital mock-up workflows, CGR allows teams to visualize the overall product without loading every editable CATIA component. This supports packaging studies, space reservation, ergonomic review, serviceability checks, and early collaboration between disciplines.

In supply chain collaboration, CGR can be used when a supplier, customer, or internal department needs to view a design but does not need full feature history or editable CAD data. This can reduce file size and limit exposure of some design details, although the external shape of the part is still visible.

In PLM and PDM environments, CGR may be used as a lightweight visualization asset associated with CATIA product structures. This helps users preview and review components without opening the complete authoring model.

In visualization and downstream data pipelines, CGR can provide a fast mesh-based representation for applications that need to display CATIA-derived geometry, create previews, or support lightweight collaboration workflows.

Challenges or Common Pitfalls

A common mistake is treating CGR as exact CAD geometry. A CGR file may look like the original CATIA model, but it is based on tessellated facets rather than precise B-Rep surfaces. Measurements, intersections, and geometric checks performed on CGR data should therefore be treated as approximate unless the workflow explicitly loads exact geometry.

Another pitfall is assuming that CGR can be edited like a CATPart. CGR does not preserve the parametric feature tree, constraints, or construction history required for design modification. Once a workflow becomes CGR-only, design intent is largely lost.

CGR can also create problems when users expect complete metadata. Part numbers, materials, revisions, PMI, assembly constraints, and product structure may be incomplete or unavailable depending on how the CGR was generated and exchanged.

Version drift is another issue. If the source CATPart or CATProduct changes but the CGR cache is not updated, the visual representation may no longer match the authoritative model. This can create discrepancies during review or collaboration.

Assembly-level CGR has additional limitations. It may simplify or flatten product structure and should not be used as a substitute for the complete CATProduct when full assembly intelligence is required.

Finally, CGR still exposes the external shape of a model. In intellectual property-sensitive workflows, this may be useful when teams want to share less than a full native model, but it does not make the geometry confidential by default.

How Spatial Helps

Spatial’s 3D InterOp supports workflows where applications need to read and use CATIA V5 data, including lightweight visualization data and exact geometry depending on the requirements of the downstream process.

For visualization-oriented workflows, 3D InterOp can be used to access tessellated CATIA V5 representation data when a lightweight model is sufficient. This can help developers build applications that need fast model loading, previews, digital mock-up, or review workflows.

When exact geometry is required, 3D InterOp can support access to CATIA V5 B-Rep data instead of relying only on the CGR approximation. This distinction is important for workflows such as manufacturing, simulation preprocessing, model repair, and precise CAD translation.

Spatial modeling technologies such as 3D ACIS Modeler and CGM Modeler can also support applications that need robust geometry operations after CAD data is imported. In a typical workflow, CATIA-derived data may be read, checked, healed, translated, visualized, or prepared for downstream engineering use.

For software developers, this allows CGR and CATIA V5 data to be integrated into broader CAD, CAM, CAE, PLM, metrology, robotics, additive manufacturing, or visualization pipelines without treating lightweight tessellation and exact B-Rep geometry as interchangeable.

Other File Formats