pointcloudprocessing/docs/usecase3.md

Go to the documentation of this file.

# Copyright (c) 2019-2020, NVIDIA CORPORATION.  All rights reserved.

@page pointcloudprocessing_usecase3 Point Cloud Stitching

@note SW Release Applicability: This tutorial is applicable to modules in both **NVIDIA DriveWorks** and **NVIDIA DRIVE Software** releases.

This tutorial shows how to stitch multiple point clouds in a common coordinate system.

Assume there are three individual point clouds created and accumulated. You can initialize the module:

```{.cpp}
dwPointCloud accumulatedPointClouds[3];
dwPointCloud stitchedPointCloud;
dwTransformation3f pointCloudTransformations[3];

// allocate memory for individual point cloud and stitched point cloud
......

// accumulate lidar packets to point cloud spin
......

// get transformations for each point cloud
......

dwPointCloudStitcherHandle_t stitcher;
dwPointCloudStitcher_initialize(&stitcher, context);
dwPointCloudStitcher_setCUDAStream(stream, stitcher);

for (uint32_t i = 0; i < 3; i++)
{
    dwPointCloudStitcher_bindInput(i, &accumulatedPointClouds[i], pointCloudTransformations[i], stitcher);
}

dwPointCloudStitcher_bindOutput(&stitchedPointCloud, stitcher);
```

There is an ability to apply global transformation to all stitched points. To do this:

```{.cpp}
dwPointCloudStitcher_setGlobalTransformation(&rigToWorld, stitcher);
```

In reality each point cloud was captured in a different timestamp, stitching together would cause motion artifacts.
To correct such distortion:

```{.cpp}
dwPointCloudStitcher_enableMotionCompensation(referenceTimestamp, egomotion, stitcher);
dwPointCloudStitcher_process(stitcher);
cudaStreamSynchronize(stream);
```

`egomotion` is needed to correct the distortion based on the relative egomotion between `referenceTimestamp` and individual point cloud's timestamp.
Please see @ref egomotion_usecase1 for egomotion usecase.


To release the module:

```{.cpp}
dwPointCloudStitcher_release(stitcher);
```

For more details see @ref dwx_pointcloudprocessing_sample