PhloemDocs
Markdown

Name channels and units

Give each signal a readable name and unit, and see how it is drawn. A channel is one signal from one input, named by a path like /rig/pressure, /cam/front or /arm/joint/position_deg.

Kinds

What a channel carries decides which tile (one box on Live) draws it.

KindWhat it isDrawn asSet by
scalara number or true/falsea trace on Live, a column in ReplayPhloem
texta line of texta text rowPhloem
imagea camera framea picture tilethe source
segmentation_imagea per-pixel mask over a frameoverlay on the framethe source
vectora list of numbers that belong togethera waveform tilethe source
points3da point cloudthe 3D scenethe source
boxes2dboxes drawn on a camera frameoverlay on the framethe source
boxes3dboxes in 3Dthe 3D scenethe source
transform3dwhere something sits and how it is turnedplaces the others in 3Dthe source
line_strips3dpaths, trajectories, footstep plans, polygonslines in the 3D scenethe source
arrows3dvectors from a point — velocity, force, a headingarrows in the 3D scenethe source
poses3dpositions with an orientation — a robot's pose, waypointssmall axis triads in the 3D scenethe source
mesh3da triangle mesh or a 3D model file (glTF, OBJ, STL)a solid in the 3D scenethe source
ellipsoids3dspheres and ellipsoidsshapes in the 3D scenethe source
cylinders3dcylindersshapes in the 3D scenethe source
text3dlabels pinned to points in spacetext over the 3D scenethe source
grid_mapan occupancy grid, costmap or height mapa raster laid in the 3D scenethe source
pinholea camera's field of viewa frustum in the 3D scenethe source
depth_imagedistance per pixela depth-shaded picture tilethe source
geo_pointsGPS fixesdots and a track on the Mapthe source
geo_line_stringsa route or track on the Eartha line on the Mapthe source
points2dkeypoints on a camera frameoverlay on the framethe source
line_strips2dlines and circles on a camera frameoverlay on the framethe source
text2dlabels on a camera frameoverlay on the framethe source

Phloem recognises numbers and text. Everything else arrives as bytes, so the source must say which kind it is. Recordings do this through their topic types: a ROS path lands as line_strips3d, a Foxglove point cloud as points3d, a GPS fix as geo_points.

When the machine is online, the Map draws OpenStreetMap streets. Pick another source with the tile button on the panel. Offline, the track still draws over a plain grid.

Nothing is drawn

A channel of bytes with no kind still records and replays, but nothing draws it.

Comes fromFix
a Push endpointsay image or segmentation_image in the body — Send your own data
a connectorthe connector decides; if it says nothing, raise it there
a recordingthe file's own topic types decide it
Note

A kind takes effect on the channel's next sample. You don't need to re-import anything.

Paths

  • A missing leading / is added: temp1 becomes /temp1. Empty segments (//cam, a trailing /) are refused.
  • A structured message becomes one channel per field (/imu/data/orientation/x), and an array one per position (/scan/ranges/0).
  • Where you type a path, as in a pipeline step or Trellis rule, ** matches everything below it: /motor/**.
  • Names and units belong to the path, not the input. Swap the box behind /daqmx/Dev1/ai0 and rig pressure stays with the path.

Name a channel, set its unit

Add input has a Channels section with one row per channel: the end of the path, a name box and a unit box. The same rows show when you edit the input later.

  1. Type the name you want to see, like rig pressure.
  2. Type the unit, like bar.
  3. Click away from the box to save. Add & start does not save it.

Your unit replaces the device's own unit everywhere. Clear the box to use the device's unit again.

A board that can list its channels fills the rows straight away. Other inputs fill them once data arrives. Until then the section reads No channels yet — start the input and they will appear here, ready to name.

Waveform tiles

A waveform is one channel holding a list of numbers at one moment, with a label for each slot. Six joint angles are one channel on a J1…J6 axis, not six channels. A source calls this kind vector.

  • Named slots draw as bars, a continuous range as a line. The labels decide.
  • peak hold keeps each slot's highest value on screen, so you don't miss a spike.
  • In Replay you see the sample at the cursor, or No sample at this cursor. It never shows a newer one instead.

A robot's sensor_msgs/JointState is not a waveform. Each joint is its own number channel, named by the robot: /joint_states/position/left_hip_pitch, /joint_states/effort/left_hip_pitch. A safety limit can then watch one joint, and a chart can pick the joints it wants. If the message has no names, the channels are numbered (…/position/0, /1, …).

You cannot send a waveform by hand. It comes from a source that makes one, or from a pipeline step that builds one.

A safety limit checks one number, so it cannot watch a whole waveform. Put the limit on a number channel instead. A Derive channel step on Pipelines makes one from the raw signal.

Updated