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Limitations in Revit renderings

Kurt Bieri

The added value of BIM planning essentially lies in the workflow as a whole and in the information on the materials and products used in a building. 

To achieve this, ReluxNet® makes available Revit Family Files on 100 manufacturers and constantly adapts these to market requirements.

In the basic version, Revit also contains an artificial light and daylight renderer. 

Relux does not check whether this operates in a physically correct manner. 

It can, however, be said that the conditions necessary for correct calculations are not fulfilled. 

Here are two points that would suggest that it does not calculate correctly (for Revit Versions up to 2018):

1. Incorrect interpretation of 3D geometries in conjunction with measured data for luminaires. 

The following picture shows how a light distribution curve can be embedded in a luminaire geometry, preventing the outflow of light to a certain extent.

In this example, the indirect portion is either fully or partially lost.

The only way to create physically correct conditions for a calculation at the moment is to switch off 

the visibility of the luminaire geometries prior to their calculation and visualisation.

2. Luminaires that are not calculated and visualised correctly in lighting engineering terms 

are those whose dimensions mean that they are too close to objects and thus do not respect the photometric distance law. 

Renderers that work solely with point light sources and do not subdivide flood lamps give rise to an incorrect picture.

Wrong: linear luminaire as a point light source

Right: linear luminaire with a large number of small point light sources