Visualizing camera trajectory in Open3D

[maheshkkumar]

Hi @AlexanderFabisch,

I am trying to use pytransform3d for some visualizations. So, I was wondering if there is a particular example/tutorial in the documentation related to this image in README for visualizing the camera trajectory in Open3D.

Thank you!

[AlexanderFabisch]

Hi @maheshkkumar,

there is no magic. Figure.plot_camera is all you need to read. If the explanation is not enough, let me know how to improve it.

The specific example that you refer to has been generated from the output of the software meshroom with this code:

import sys
import json
import numpy as np
import pytransform3d.transformations as pt
import pytransform3d.camera as pc
import pytransform3d.visualizer as pv


mesh_filename = sys.argv[-2]
camera_filename = sys.argv[-1]

with open(camera_filename, "r") as f:
    cameras = json.load(f)

camera_poses = cameras["poses"]
camera_intrinsics = cameras["intrinsics"][0]

px_focal_length = float(camera_intrinsics["pxFocalLength"])
px_principal_point_x = float(camera_intrinsics["principalPoint"][0])
px_principal_point_y = float(camera_intrinsics["principalPoint"][1])
M = np.array([
    [px_focal_length, 0, px_principal_point_x],
    [0, px_focal_length, px_principal_point_y],
    [0, 0, 1]
])
sensor_size = (float(camera_intrinsics["width"]), float(camera_intrinsics["height"]))

transformation_matrices = np.empty((len(camera_poses), 4, 4))
for i, camera_pose in enumerate(camera_poses):
    R = np.array(list(map(float, camera_pose["pose"]["transform"]["rotation"]))).reshape(3, 3)
    p = np.array(list(map(float, camera_pose["pose"]["transform"]["center"])))
    transformation_matrices[i] = pt.transform_from(R=R, p=p)


fig = pv.figure()
fig.plot_mesh(mesh_filename)
for pose in transformation_matrices:
    fig.plot_transform(A2B=pose, s=0.1)
    fig.plot_camera(M=M, cam2world=pose, virtual_image_distance=0.1, sensor_size=sensor_size)
fig.show()