# U3D Reader

U3D Format
File Extension | U3D
Supported Versions | ECMA-363
Platforms |
B-rep | N/A
PMI | N/A
Tessellation |
Views |
Visualization |

The U3D (Universal 3D) file format was developed by a consortium called the 3D Industry Forum (3DIF), spearheaded by Intel Corporation, and later standardized by Ecma International (as ECMA-363) in the mid-2000s to facilitate sharing 3D CAD data, especially within PDF documents.

Our U3D Reader provides access to the visualization data stored within a U3D file. The most common file extension for U3D files is .U3D.

HOOPS Exchange geometry access for U3D includes:

- Tessellation: Mesh or polygonal geometry is imported directly.
- B-rep: Not supported by this format - HOOPS Exchange treats it as tessellation only.

## How to Import From U3D

If you are new to reading models with HOOPS Exchange, see the basic load workflow </guide/basic_operations/load_model>` section of the Programming Guide.

To load a U3D file, use `A3DAsmModelFileLoadFromFile()`.

Below, the `A3DParamsLoadData` structure is used to customize the loading behavior. See our `API reference manual` for more information about this important data type.

    A3DAsmModelFile* pModelFile = 0;

    A3DRWParamsLoadData sReadParam = A3D_MAKE_DATA(A3DRWParamsLoadData);
    sReadParam.m_sGeneral.m_bReadSolids = true;

    // ... set other A3DRWParamsLoadData fields as necessary

    A3DAsmModelFileLoadFromFile("path/to/file.u3d", &sReadParam, &pModelFile);

See Simple Load and Export for general information about loading model files.

## Assembly

This concept is not supported by U3D. However, U3D files may contain multiple components or objects. HOOPS Exchange represents these as a model tree that you can traverse using the standard structure APIs.

To learn more about how HOOPS Exchange handles assemblies, see our tutorial about assembly traversal.

## B-Rep

This concept is not supported by U3D.

## Visualization

This concept is not supported by U3D.

## Views

HOOPS Exchange does not currently support U3D views.

## PMI

This concept is not supported by U3D.

## Miscellaneous

Construction geometries are handled by the reader.

### Advanced Publish

Advanced Publish is an authoring SDK within HOOPS Exchange that enables creation and export of rich engineering data using the PRC data model. It supports generating output for several supported formats, such as U3D, through file import or API-based authoring.

For more information about using Advanced Publish with this file format, refer to the Advanced Publish section of the Programming Guide here.

### Limitations

The animation stored within a particular file is not exposed to developers. However, if you are providing a U3D file to Advanced Publishing to put into a PDF document, then the U3D remains unchanged and the animation remains available and can be exposed in the PDF document.

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