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The coordinate of the dataset

#10
by Doduchuy12 - opened
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Doduchuy12

I have few questions about the coordinate of the dataset:

  1. What is the origin of the world coordinate in the top down map of the floor (in pixel)?
  2. How can I project an object in the world coordinate (meters) in the ground truth file into the pixel coordinate of the file top down map (map.png) in the data?
  3. What does the cameraMatrix mean in the calibration.json file?. It is not equal to intrinsicMatrix.dot(extrinsicMatrix)
visionNoob

hi

  1. you can get the origin with scaleFactor & translationToGlobalCoordinates. see https://huggingface.co/datasets/nvidia/PhysicalAI-SmartSpaces/discussions/9
  2. you need to apply transformations like intrinsicMatrix(camera -> pixel) @ extrinsicMatrix(world->camera) @ bev_to_world(bev->world)
  3. cameraMatrix: intrinsicMatrix @ extrinsicMatrix
zhengthomastang
 NVIDIA org

@Doduchuy12 @visionNoob Thanks for the questions.

  1. The origin of the world coordinate system corresponds to the bottom-left corner of the top-down floor map. The x-axis points to the right, and the y-axis points upward.

  2. To project an object from world coordinates (in meters) to pixel space on the top-down map (map.png), apply the following transformation:

    (coordinates + translationToGlobalCoordinates) * scaleFactor

    This converts ground-plane positions into pixel coordinates.

  3. The cameraMatrix in calibration.json represents the full projection matrix. It is equivalent to:

    intrinsicMatrix @ extrinsicMatrix

    This relationship holds after normalization, since the projection matrix is defined up to scale.

For future inquiries, please feel free to also email us at aicitychallenges@gmail.com to ensure we can respond promptly.

zhengthomastang changed discussion status to closed

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