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| import numpy as np |
|
|
| def get_intrinsics(H,W): |
| """ |
| Intrinsics for a pinhole camera model. |
| Assume fov of 55 degrees and central principal point. |
| """ |
| f = 0.5 * W / np.tan(0.5 * 55 * np.pi / 180.0) |
| cx = 0.5 * W |
| cy = 0.5 * H |
| return np.array([[f, 0, cx], |
| [0, f, cy], |
| [0, 0, 1]]) |
|
|
| def depth_to_points(depth, R=None, t=None): |
|
|
| K = get_intrinsics(depth.shape[1], depth.shape[2]) |
| Kinv = np.linalg.inv(K) |
| if R is None: |
| R = np.eye(3) |
| if t is None: |
| t = np.zeros(3) |
|
|
| |
| M = np.eye(3) |
| M[0, 0] = -1.0 |
| M[1, 1] = -1.0 |
|
|
| height, width = depth.shape[1:3] |
|
|
| x = np.arange(width) |
| y = np.arange(height) |
| coord = np.stack(np.meshgrid(x, y), -1) |
| coord = np.concatenate((coord, np.ones_like(coord)[:, :, [0]]), -1) |
| coord = coord.astype(np.float32) |
| |
| coord = coord[None] |
|
|
| D = depth[:, :, :, None, None] |
| |
| pts3D_1 = D * Kinv[None, None, None, ...] @ coord[:, :, :, :, None] |
| |
| pts3D_1 = M[None, None, None, ...] @ pts3D_1 |
| |
| pts3D_2 = R[None, None, None, ...] @ pts3D_1 + t[None, None, None, :, None] |
| |
| |
| return pts3D_2[:, :, :, :3, 0][0] |
|
|
|
|
| def create_triangles(h, w, mask=None): |
| """ |
| Reference: https://github.com/google-research/google-research/blob/e96197de06613f1b027d20328e06d69829fa5a89/infinite_nature/render_utils.py#L68 |
| Creates mesh triangle indices from a given pixel grid size. |
| This function is not and need not be differentiable as triangle indices are |
| fixed. |
| Args: |
| h: (int) denoting the height of the image. |
| w: (int) denoting the width of the image. |
| Returns: |
| triangles: 2D numpy array of indices (int) with shape (2(W-1)(H-1) x 3) |
| """ |
| x, y = np.meshgrid(range(w - 1), range(h - 1)) |
| tl = y * w + x |
| tr = y * w + x + 1 |
| bl = (y + 1) * w + x |
| br = (y + 1) * w + x + 1 |
| triangles = np.array([tl, bl, tr, br, tr, bl]) |
| triangles = np.transpose(triangles, (1, 2, 0)).reshape( |
| ((w - 1) * (h - 1) * 2, 3)) |
| if mask is not None: |
| mask = mask.reshape(-1) |
| triangles = triangles[mask[triangles].all(1)] |
| return triangles |
|
|