Single-frame export
Use a single selected frame when you need a representative scan for a bug report, scene check, annotation test, or small point-cloud example.
PointCloud2 frame extraction
ROS 2 MCAP Frame Extractor — Download PointCloud2 Frames
Extract binary PCD samples from a supported ROS 2 MCAP PointCloud2 recording without installing ROS 2 or uploading the file. WolkeViz exports the current frame, every Nth frame, or an approximately fixed number of frames distributed across a selected range or the entire sequence.
At a glance
What to know before opening the file
Regular interval sampling
Choose every n frames when the recording has a stable enough cadence and you want a predictable temporal interval without exporting every message.
Distributed sampling
Choose a range and target count when you want approximately that many deterministic frames spread across the inclusive range instead of one consecutive block.
Practical workflow
Build a traceable PCD frame sample
- Open the supported MCAP recording and select the PointCloud2 topic to extract.
- Inspect the timeline and set a start and end frame that cover the event or route segment you need.
- Choose one frame, every n frames, or a requested number of equally spaced frames.
- Download the selected frames and retain the source topic, timestamps, and selection rule in the resulting dataset notes.
Technical notes
Choosing frames is a data-curation decision
A recording may contain multiple point-cloud topics at different rates. Select the intended channel first; otherwise a correct frame-selection rule can still produce the wrong sensor data.
For every-N sampling, output follows message order within the selected inclusive range. For target-count sampling, deterministic frame indices are distributed across that range. The point budget affects only the display; supported export sources are decoded again at source resolution.
Multiple frames are written as binary PCD files in a ZIP with a wolkeviz-export.json provenance manifest. PCD does not carry complete LAS-style CRS metadata, and WolkeViz does not apply TF or pose alignment. Very large jobs remain limited by browser memory because the final ZIP must fit in memory before download.
See it in use
Watch the workflow.
See WolkeViz open and inspect a ROS 2 MCAP point-cloud recording in the browser.
Questions and answers
Common questions
Can I download multiple PointCloud2 frames from MCAP?
Yes. WolkeViz can export every Nth frame or an approximately fixed number of distributed frames from an inclusive range or the entire supported PointCloud2 sequence.
What does evenly spaced frame extraction mean?
It selects frames distributed across the chosen start/end range. It is useful when you want a fixed-size sample that covers the sequence rather than a consecutive block.
Do I need to convert the whole MCAP file first?
No. For supported PointCloud2 recordings, a browser workflow can select and export the frames you need without a separate full-file conversion step.
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