AVF, Ray Tracing and Signal Attenuation

I have been a bit quieter in the Revit API discussion forum in the past day or two.


Well, I implemented a neat new little sample add-in, RvtFader.

In a rather simplified manner, it calculates and displays signal attenuation caused by distance and obstacles, specifically walls.

That provided an opportunity for me to dive in again into two very interesting pieces of Revit API functionality:

In the course of implementing the AVF part of things, I also resuscitated my trusty old RevitWebcam add-in.


RevitWebcam uses AVF and an external event to display a live webcam image on a selected element face.

The external event polls the webcam for updated images at regular intervals.

I now created a new GitHub repository to host this add-in and migrated it to Revit 2017.

Here it is displaying a webcam image on a wall:

RevitWebcam in action in Revit 2017

Back to RvtFader, though:


RvtFader is a Revit C# .NET API add-in to calculate and display signal attenuation using the analysis visualisation framework AVF and ReferenceIntersector ray tracing.



This application works in a Revit model with a floor plan containing walls.

It calculates the signal attenuation caused by distance and obstacles.

In the first iteration, the only obstacles taken into account are walls.

Two signal attenuation values in decibels are defined in the application settings:

Given a source point, calculate the attenuation in a widening circle around it and display that as a heat map.


To achieve this task, RvtFader implements the following:

Summary of the steps towards achieving this:

RvtFader displaying distance using AVF

Graphical debugging displaying model lines

Attenuation calculation results

For more details on the implementation steps, please refer to the list of releases and commits.

Further Reading