What is Autodesk Revit?
Autodesk Revit is a BIM software tool for architects, engineers, and construction professionals to model shapes, structures, and systems in 3D. It stores these 3D models in a proprietary RVT file format with the .rvt file extension.
These RVT files contain:
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A geometry model of a building or facility, including spatial elements, materials, and shapes
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A so-called feature data model describing typical BIM properties of that data, such as layer, material, and so on
LuciadLightspeed can decode both the geometry and the feature data, handling the two data types in a distinct way.
Geometry model: conversion to OGC 3D Tiles
If you load Revit data directly in LuciadLightspeed, it is converted internally to an OGC 3D Tiles dataset, on-the-fly.
You can also convert the data to OGC 3D Tiles up front, as described in the Converting Revit data to OGC 3D Tiles tutorial.
See the OGC 3D Tiles documentation for more information about that data format. |
During the conversion, the Revit data undergoes a number of changes to make it more suitable for decoding and visualization.
Tile structuring
OGC 3D Tiles datasets have a tile structure that is optimized for streaming.
Revit data doesn’t have a tiling structure. Therefore, the data is organized into a new tile structure during the conversion. Due to the nature of CAD data, tiles can still overlap, though.
Generation of 3D meshes and levels-of-detail
The conversion process generates 3D meshes for the original geometries at multiple levels-of-detail by means of distinct quality settings for each level. At lower levels-of-detail, smaller objects are left out.
Metadata
The conversion process doesn’t store the metadata of the original Revit data in the OGC 3D Tiles dataset. It does generate a unique FeatureID for every object, though, and stores the feature IDs in the batch table information of the OGC 3D Tiles dataset.
Using this FeatureID, you can link the metadata inside the feature data model to the OGC 3D Tiles data.
Performance impact of the conversion
The internal conversion of Revit data affects LuciadLightspeed performance:
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Because all geometric information of the Revit data is interpreted before the OGC 3D Tiles structure is created, it can take a long time for a dataset to load.
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All geometric information of the Revit data and the resulting OGC 3D Tiles structure must be kept in memory, resulting in a large memory footprint.
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The 3D mesh of each tile is calculated on-the-fly, resulting in a high CPU load.
As a consequence, it is typically not practical to visualize the Revit data model directly on a Lightspeed map.
Therefore, the recommended way of handling Revit data in LuciadLightspeed is converting the data in the OGC 3D Tiles format up front, and visualizing the OGC 3D Tiles data on a Lightspeed map, as explained in the Converting Revit data to OGC 3D Tiles tutorial.
Feature data model: make the feature data available
The Revit decoder can also decode the Revit data to a feature data model. This model contains the metadata of the Revit objects. The elements in this feature model have a FeatureID property, which corresponds to the Revit objects in the OGC 3D Tiles dataset.
A client application must load the feature data separately from the geometry data. To allow the client application to load the feature data, you must expose the data. You have several options to do so:
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Convert the feature model to GeoJSON, with each GeoJSON feature containing the metadata of the original Revit data. For more information, see the Converting Revit data to GeoJSON tutorial.
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Serve the feature model as a WFS service in LuciadFusion. For more details, refer to the BIM serving article in the LuciadFusion documentation.