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2022-09-19 17:08:24 -0500 | marked best answer | PointCloud2 Storage Format Hi, I am trying to implement in FPGA a ROS publisher node of PointCloud2 messages. As a first step, i have already implemented a publisher node on the FPGA that is publishing strings. Now, i am trying to do the same but for the PointCloud2 message format. It is very simple to understand how a string is stored, basically each character is converted to its ASCII value and stored (as it can be seen here). On the other hand, a PointCloud2 is a complex data type that is not so easy to understand. I have made some progress on understanding how the metadata of a PointCloud2 is stored, however, it is being very difficult to understand the storage of the data part of the PointCloud2 data type. To simplify, I have also tried a PointCloud2 with only one point but i couldn't decode it either. I know that the X, Y and Z are sequentially ordered with 4 bytes each (the datatype is a Float32). Therefore, i can isolate the 4 bytes corresponding to one of the coordinates. I have tried to assign to the X coordinate the values from 0 to 17 (in decimal). This are the values stored when using these values (they are all in decimal): 1 = [0, 0, 128, 63] -> little-endian so, the most significant byte is 63 followed by, 128, 0, 0 2 = [0, 0, 0, 64] 3 = [0, 0, 64, 64] 4 = [0, 0, 128, 64] 5 = [0, 0, 160, 64] 6 = [0, 0, 192, 64] 7 = [0, 0, 224, 64] 8 = [0, 0, 0, 65] 9 = [0, 0, 16, 65] 10 = [0, 0, 32, 65] 11 = [0, 0, 48, 65] 12 = [0, 0, 64, 65] 13 = [0, 0, 80, 65] 14 = [0, 0, 96, 65] 15 = [0, 0, 112, 65] 16 = [0, 0, 128, 65] 17 = [0, 0, 136, 65] So, my question is, how are the values stored? Supposedly the data part is stored in binary blobs according to here. However, i don't understand what does this mean and how it works. Also, i have not found any concrete example on how to convert a decimal value to this representation. For a PointCloud2 with X, Y and Z my current understanding is the following (here is the corresponding data): header:
height: 4 bytes width: 4 bytes fields:
is_bigendian: 1 byte point_step: 4 bytes row_step: 4 bytes size: 4 bytes data: size bytes is_dense: 1 byte |
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2021-07-16 09:53:18 -0500 | edited question | PointCloud2 Storage Format PointCloud2 Storage Format Hi, I am trying to implement in FPGA a ROS publisher node of PointCloud2 messages. As a firs |
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2021-07-14 11:05:55 -0500 | answered a question | PointCloud2 Storage Format As I selected the datatype 7 (FLOAT32) the data part is stored as indicated in the standard IEEE 754 (which is a widely |
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2021-07-08 12:41:24 -0500 | asked a question | PointCloud2 Storage Format PointCloud2 Storage Format Hi, I am trying to implement in FPGA a ROS publisher node of PointCloud2 messages. As a firs |
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2021-02-08 19:44:50 -0500 | asked a question | Publisher doesn't respond when more processing is required Publisher doesn't respond when more processing is required Hi, I have a ROS Node that is responsible for reading data |
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