Up until now we have been measuring the position of markers, but we can also use the position of a series of markers to measure the speed of their movement. Speed is really a measure of distance over time. The time increment we receive data from Vicon Tracker is 100 times a second. This means we would be measuring the change in position of a marker over 0.01 seconds. For instance, when that distance is greater it means the speed is faster.
To measure the speed we simply need to find the distance between the latest marker position and its previous position.
We can easily measure the distance between the current and previous marker coordinates with the Data Recorder component in Grasshopper by setting the record limit to 2. This will give us a list of the current position and the previous position. We can then get the distance between those two vectors and that will be the current speed of the marker movement.
The above definition uses the distance between the current and previous coordinate (speed) to define the radius of a circle. You can download the definition here: Speed
Speed cam be used to control a number of other components and geometry. In the example above the definition is creating s line segment between each of the recorded points of one marker. The segments are piped with a radius determined by the speed. The speed per line segment is remapped to a domain of 0-1 to determine the color of each piped surface using the gradient component.
You can download the above definition here: Speed+Color+Pipe