The OpenVR CHOP receives positional data, frame rendering info, and action data from the OpenVR SDK. Each CHOP can output in one of 5 modes: Sensors, Projection Matrices, Controllers, Frame Timings, and Actions.
Actions are a set of values that can be bound to controller inputs through SteamVR.
TouchDesigner defines its list of actions and are available to be bound through the SteamVR Binding tool. TouchDesigner provides a default binding for the HTC Vive Controller, but these bindings can be overridden. Bindings for a variety of other devices can also be added.
To add/edit bindings: from the SteamVR menu select "Devices" -> "Controller Input Binding", then select TouchDesigner099.exe from the list of available applications. This will open up the binding creation page for TouchDesigner. If the Vive Controller is selected, a default binding will be on the creation page that can be used. Note: for TouchDesigner099.exe to appear in the application list OpenVR must be initialized, which means that TouchDesigner must be open and there must be an OpenVR OP in the network.
These are available actions for both left and right controllers, with an explanation of their default binding on HTC Vive Controller:
- Hand Pose: Transform matrix, bound to the transform of the controller.
- Trigger: Boolean value, bound to if the trigger is fully pulled.
- Squeeze: Float value, bound to the current pulled position of the trigger.
- Grip: Boolean value, bound to the grip buttons (on the side).
- Trackpad: X/Y value, bound to the position of finger on the trackpad.
- Trackpad Click: Boolean value, bound to the trackpad button.
- Trackpad Touch: Boolean value, bound to the trackpad touch.
- Joystick: X/Y value, unbound on the HTC Vive Controller.
- Joystick Click: Boolean value, unbound on the HTC Vive Controller.
- A Button: Boolean value, bound to the Application Menu button.
- B Button: Boolean value, bound to the System button.
Getting Sensor Data at Higher Rates
By default when running a VR system the file will be throttled to the speed of the VR devices refresh rate by the OpenVR SDK. This helps ensure the low latency output required for a good VR experience. If only controllers/Vive trackers are being used for tracking in a non-VR situation, the file can run and sample those devices at a higher sample rate as long as no OpenVR TOP in the project. If an OpenVR TOP is present anywhere in the project, then playback will be throttled to the VR devices refresh rate.
Parameters - Setup Page
active - Control if this node is querying data from the OpenVR driver.
output - ⊞ - Controls what kind of category of data will be output from this node.
sensor- Output data such as sensor orientation and general information such as render resolution.
- Projection Matrices
projmatrices- Output the projection matrices for each eye.
controllers- Output controller states.
- Frame Timings
frametimings- General information regarding frame rendering.
actions- The values of the bindable Actions. Actions can be bound to controller inputs using the SteamVR configuration tool. TouchDesigner provides a default binding for the HTC Vive Controller.
maxcontrollers - The maximum number of controller whose data should be output from this node.
firstcontroller - The first controller number to be output. For example if this is set to 2 and Max Controllers is 2, then data for controllers 2 and 3 will be output.
orientation - When doing 'Sensor' output, controls of the orientation channels will be output. By default the units for orientation are 1 unit = 1 meter.
generalinfo - When doing 'Sensor' output, controls of general information channels will be output, such as render resolution and play area size.
near - When outputting 'Projection Matrices', controls the near plane the projection matrix will be built with.
far - When outputting 'Projection Matrices', controls the far plane the projection matrix will be built with.
unitscale - OpenVR by default works in a scale where 1 unit = 1 meter. This parameter allows the scale to be changed incase a scene is imported with a different scale.
Parameters - Common Page
timeslice - Turning this on forces the channels to be "Time Sliced". A Time Slice is the time between the last cook frame and the current cook frame.
scope - To determine which channels get affected, some CHOPs use a Scope string on the Common page.
Sample Rate Match
srselect - ⊞ - Handle cases where multiple input CHOPs' sample rates are different. When Resampling occurs, the curves are interpolated according to the Interpolation Method Option, or "Linear" if the Interpolate Options are not available.
- Resample At First Input's Rate
first- Use rate of first input to resample others.
- Resample At Maximum Rate
max- Resample to the highest sample rate.
- Resample At Minimum Rate
min- Resample to the lowest sample rate.
- Error If Rates Differ
err- Doesn't accept conflicting sample rates.
exportmethod - ⊞ - This will determine how to connect the CHOP channel to the parameter. Refer to the Export article for more information.
- DAT Table by Index
datindex- Uses the docked DAT table and references the channel via the index of the channel in the CHOP.
- DAT Table by Name
datname- Uses the docked DAT table and references the channel via the name of the channel in the CHOP.
- Channel Name is Path:Parameter
autoname- The channel is the full destination of where to export to, such has
autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.
exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).
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Binding is a Parameter Mode that ties two or more parameters together, where changing the value of any one of the bound parameters changes value of all the bound parameters. The actual value is stored in one of bound parameters, called the bind master parameter.
A Time Slice is the time from the last cook frame to the current cook frame. In CHOPs it is the set of short channels that only contain the CHOP channels' samples between the last and the current cook frame.
A parameter in most CHOPs that restricts which channels of that CHOP will be affected. Normally all channels of a CHOP are affected by the operator.
samples-per-second of a CHOP. Each CHOP in your network has a sample rate, whether it is used or not. The overall timeline has a "frame rate", which is the number of animation frames per second, generally your monitor display frequency.
Exporting is the connection of CHOP channels to parameters of operators. The output of each exporting CHOP is one or more channels, active only while the CHOP Viewer is on. The current value of a channel can be exported to a parameter of any operator, overriding that parameter's value. See Parameter.
Parameters in TouchDesigner are an operator's settings (numbers, menus, flags, strings, paths) which the user can alter. Parameters for any operator can be opened by right-clicking on the operator and selecting "Parameters..." A currently selected operator's parameters can be viewed in a Network Editor by pressing the keyboard shortcut 'p'.