Transform_train.json file analysis

File content analysis

{
    
    
    "camera_angle_x": 0.6911112070083618,
    "frames": [
        {
    
    
            "file_path": "./train/r_0",
            "rotation": 0.012566370614359171,
            "transform_matrix": [
                [
                    -0.9999021887779236,
                    0.004192245192825794,
                    -0.013345719315111637,
                    -0.05379832163453102
                ],
                [
                    -0.013988681137561798,
                    -0.2996590733528137,
                    0.95394366979599,
                    3.845470428466797
                ],
                [
                    -4.656612873077393e-10,
                    0.9540371894836426,
                    0.29968830943107605,
                    1.2080823183059692
                ],
                [
                    0.0,
                    0.0,
                    0.0,
                    1.0
                ]
            ]
        }
 	]
 }

This JSON file appears to be a configuration file used to describe camera and frame information, commonly used in computer graphics. Let me explain what's in it:

• "camera_angle_x": 0.6911112070083618: This value represents the horizontal viewing angle (angle) of the camera, that is, the width of the field of view. It describes the horizontal range of the camera from left to right.

• "frames": This is a list containing multiple frames. Each frame describes a different perspective or camera position within a scene.

  • "file_path": "./train/r_0": This value represents the file path of a frame. May be the path to an image file.

  • "rotation": 0.012566370614359171: This value represents the rotation angle of the frame relative to a reference position. Usually the angle of rotation about some axis.

  • "transform_matrix": This matrix describes the transformation information of a frame, usually the camera's transformation matrix, used to transform objects from the world coordinate system to the camera coordinate system. This matrix is ​​a 4x4 matrix, including translation, rotation and scaling information.

    Each row of this matrix represents a row of the transformation matrix, the first three rows are the rotation and scaling parts, and the last row is the translation part.

    For example, the first line [-0.9999021887779236, 0.004192245192825794, -0.013345719315111637, -0.05379832163453102]represents the rotation and scaling transformation parts.

    The second line [-0.013988681137561798, -0.2996590733528137, 0.95394366979599, 3.845470428466797]represents the transformed position information.

    The last row [0.0, 0.0, 0.0, 1.0]represents the last row of the transformation matrix.

The content of this JSON file is usually used to describe the camera perspective and the transformation relationship between different frames in the scene, and is used for computer graphics tasks such as graphics rendering and visual effects generation.

transform_matrix

When it comes to transformation matrices in graphics, a 4x4 matrix is ​​usually used. This matrix can represent a series of transformation operations such as translation, rotation, and scaling. The following is an abstract representation of the transformation matrix, with the meaning of each symbol explained:

|  s_x * r_11   s_y * r_12   s_z * r_13   t_x |
|  s_x * r_21   s_y * r_22   s_z * r_23   t_y |
|  s_x * r_31   s_y * r_32   s_z * r_33   t_z |
|      0            0            0          1  |

in:

s_x, s_y, s_z: represent the scaling factors along the x, y and z axes respectively.
r_11, r_12, r_13: Unit vector representing the transformed x-axis direction.
r_21, r_22, r_23: Unit vector representing the transformed y-axis direction.
r_31, r_32, r_33: Unit vector representing the transformed z-axis direction.
t_x, t_y, t_z: represent the translation amount on the x, y and z axes respectively.
The last line is [0, 0, 0, 1], which is used to represent the constant terms in homogeneous coordinates.

This matrix can be used to describe the transformation from the world coordinate system to the camera coordinate system, or other types of transformation operations. The meaning of each part is as described above, and together they form a complete transformation matrix that converts input points or vectors into output points or vectors.