1+ import numpy as np
2+ import torch
3+
4+
5+ def create_camera_to_world_matrix (elevation , azimuth ):
6+ elevation = np .radians (elevation )
7+ azimuth = np .radians (azimuth )
8+ # Convert elevation and azimuth angles to Cartesian coordinates on a unit sphere
9+ x = np .cos (elevation ) * np .sin (azimuth )
10+ y = np .sin (elevation )
11+ z = np .cos (elevation ) * np .cos (azimuth )
12+
13+ # Calculate camera position, target, and up vectors
14+ camera_pos = np .array ([x , y , z ])
15+ target = np .array ([0 , 0 , 0 ])
16+ up = np .array ([0 , 1 , 0 ])
17+
18+ # Construct view matrix
19+ forward = target - camera_pos
20+ forward /= np .linalg .norm (forward )
21+ right = np .cross (forward , up )
22+ right /= np .linalg .norm (right )
23+ new_up = np .cross (right , forward )
24+ new_up /= np .linalg .norm (new_up )
25+ cam2world = np .eye (4 )
26+ cam2world [:3 , :3 ] = np .array ([right , new_up , - forward ]).T
27+ cam2world [:3 , 3 ] = camera_pos
28+ return cam2world
29+
30+
31+ def convert_opengl_to_blender (camera_matrix ):
32+ if isinstance (camera_matrix , np .ndarray ):
33+ # Construct transformation matrix to convert from OpenGL space to Blender space
34+ flip_yz = np .array ([[1 , 0 , 0 , 0 ], [0 , 0 , - 1 , 0 ], [0 , 1 , 0 , 0 ], [0 , 0 , 0 , 1 ]])
35+ camera_matrix_blender = np .dot (flip_yz , camera_matrix )
36+ else :
37+ # Construct transformation matrix to convert from OpenGL space to Blender space
38+ flip_yz = torch .tensor (
39+ [[1 , 0 , 0 , 0 ], [0 , 0 , - 1 , 0 ], [0 , 1 , 0 , 0 ], [0 , 0 , 0 , 1 ]]
40+ )
41+ if camera_matrix .ndim == 3 :
42+ flip_yz = flip_yz .unsqueeze (0 )
43+ camera_matrix_blender = torch .matmul (flip_yz .to (camera_matrix ), camera_matrix )
44+ return camera_matrix_blender
45+
46+
47+ def normalize_camera (camera_matrix ):
48+ """normalize the camera location onto a unit-sphere"""
49+ if isinstance (camera_matrix , np .ndarray ):
50+ camera_matrix = camera_matrix .reshape (- 1 , 4 , 4 )
51+ translation = camera_matrix [:, :3 , 3 ]
52+ translation = translation / (
53+ np .linalg .norm (translation , axis = 1 , keepdims = True ) + 1e-8
54+ )
55+ camera_matrix [:, :3 , 3 ] = translation
56+ else :
57+ camera_matrix = camera_matrix .reshape (- 1 , 4 , 4 )
58+ translation = camera_matrix [:, :3 , 3 ]
59+ translation = translation / (
60+ torch .norm (translation , dim = 1 , keepdim = True ) + 1e-8
61+ )
62+ camera_matrix [:, :3 , 3 ] = translation
63+ return camera_matrix .reshape (- 1 , 16 )
64+
65+
66+ def get_camera (
67+ num_frames ,
68+ elevation = 15 ,
69+ azimuth_start = 0 ,
70+ azimuth_span = 360 ,
71+ blender_coord = True ,
72+ extra_view = False ,
73+ ):
74+ angle_gap = azimuth_span / num_frames
75+ cameras = []
76+ for azimuth in np .arange (azimuth_start , azimuth_span + azimuth_start , angle_gap ):
77+ camera_matrix = create_camera_to_world_matrix (elevation , azimuth )
78+ if blender_coord :
79+ camera_matrix = convert_opengl_to_blender (camera_matrix )
80+ cameras .append (camera_matrix .flatten ())
81+
82+ if extra_view :
83+ dim = len (cameras [0 ])
84+ cameras .append (np .zeros (dim ))
85+ return torch .tensor (np .stack (cameras , 0 )).float ()
86+
87+
88+ def get_camera_for_index (data_index ):
89+ """
90+ 按照当前我们的数据格式, 以000为正对我们的情况:
91+ 000是正面, ev: 0, azimuth: 0
92+ 001是左边, ev: 0, azimuth: -90
93+ 002是下面, ev: -90, azimuth: 0
94+ 003是背面, ev: 0, azimuth: 180
95+ 004是右边, ev: 0, azimuth: 90
96+ 005是上面, ev: 90, azimuth: 0
97+ """
98+ params = [(0 , 0 ), (0 , - 90 ), (- 90 , 0 ), (0 , 180 ), (0 , 90 ), (90 , 0 )]
99+ return get_camera (1 , * params [data_index ])
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