Motion Prediction

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Motion Prediction

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Navigation:  Widget Designer > Nodes > Input Nodes > Devices Input > ID Tag Tracker Input >

Motion Prediction

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This topic explains the section "Motion Prediction" of the ID Tag node, for general information about IR ID tracking and links to other chapters please see the topic ID Tag Tracker.

wd_nodes_input_id-tag-tracker_motion-prediction

This section includes settings for smoothing, predicting and damping a tag's position. For predicting where the tag will be in the next frame, a complex formula is needed. Depending on the specific movement of your tag, some factors need to be adjusted. A fast movement without abrupt stops is very different to a slow continuous one.
The factors include adjustments for velocity and acceleration. However, the most important settings are "Smoothing", "Time" and "Damping". For most tracking scenarios, the Velocity and Acceleration settings can stay on there default values.

Smoothing

The prediction calculation includes an internal velocity and acceleration part. The "Smoothing" value smoothes this data. It can be understood as a multiplying factor. The smaller Smoothing is, the more the data is damped and modified to reduce noise. Recommended values of 0.1 - 0.2 result in a lot of smoothing as commonly there is much data noise that needs to be reduced.
The higher it is, the more the VA-part influences the prediction calculation. A factor of 1 means no data modification, no smoothing.

Time (ms)

"Time" should be adjusted to meet the real duration that exists between measuring the tag's position and seeing or hearing the result, e.g. projecting an image onto this position. This delay is measured in milliseconds. Delay times up to 80-120ms are common.

Blend VA
V Start
A Start

The velocity and acceleration part contribute to the calculation as soon as a "Start" value is met. In other words, if the velocity (and acceleration respectively) is below that start value, the VA-part is not taken into account. Velocity is measured in mm/sec and Acceleration in mm/sec². If your tag jitters slightly eventhough the tag does not move at all, you can raise the VA Start to 0.3 mm for instance to discard the VA-prediction for these small movements
Blend VA blends between these two formulas with and without the VA-part.

Lighting and Aux. Tracking

This applies when you have a node attached to the ID Tag Tracker node. Per default you see in the node's input drop-down list, that every tag is expressed with a position (X, Y, Z). In case you have more than one device following the tracking it might be needed to add different damping times to the XYZ-position to route them to different output nodes. When enabling "Lighting (PSN)" you will see that each tag has an additional X2, Y2 and Z2 value; when enabling "Auxiliary Tracking" X3, Y3 and Z3 are available. As soon as you add different damping times (see below) to these values, they will not coincide any more.
Please note that the two check boxes are not of interest when outputting PSN data directly from the node!

Post Damping

This activates an additional damping calculation.
"Damping" is similar to the "Smoothing" as it smoothes the data. But as "Damping" happens at the very end of the calculation, after prediction, it can be understood as a post damping that smoothes the predicted curve to reduce jittering.
"Post Damping" can be applied to three data sets introduced above. You can setup different damping times to...:
- "XYZ Tracking Values" = X1 Y1 Z1 (default values of the node)
- "Lighting (PSN)" = PSN output send out directly from the node as well as X2 Y2 Z2 if the left check box is ticked
- "Auxiliary Tracking" = X3 Y3 Z3 if the left check box is ticked
You can set up damping times to adjust the tracking behavior for different devices. A factor of 1 means no data modification, no damping whilst values between 0 and 0.1 mean a lot damping.