RTX LiDAR: timestamp length is ~half of point count (XT32 / dual-return), cannot map 1:1 to XYZ

[dreamroboat]

Description

When using RTX LiDAR in Isaac Sim (tested with the built-in Hesai PandarXT-32 10Hz config), exampel the output from IsaacExtractRTXSensorPointCloudNoAccumulator always returns a timestamp array whose length is approximately half of the point cloud data length (often len(timestamp) ≈ len(data)/2 ± 1). This makes it impossible to associate a unique timestamp per point (XYZ) using this annotator. Besides, info.numChannels/numEchos is always zero

I also attempted the recommended approach of using IsaacCreateRTXLidarScanBuffer (expecting “timestamp of each return”), but the timestamp length still remains ~half of the number of returns/points in my setup. This behavior is consistent across frames.

Isaac Sim version

5.1.0

Operating System (OS)

22.04

GPU Name

RTX 4090

GPU Driver and CUDA versions

Driver Version: 560.35.05 , CUDA Version: 12.6

Logs

Additional information

No response

[zwdoescode]

Hi @dreamroboat ! Thanks for bringing this issue up. This is a known issue and our internal engineers are working on this.
A similar post https://forums.developer.nvidia.com/t/rtx-lidar-scan-buffer-timestamp-count-is-half-of-the-point-cloud-size/354993