Create geometry.py

geometry.py

@@ -0,0 +1,72 @@
+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 converts from your coordinate to PyTorch3D's coordinate system
+    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)  # z=1
+    coord = coord.astype(np.float32)
+    # coord = torch.as_tensor(coord, dtype=torch.float32, device=device)
+    coord = coord[None]  # bs, h, w, 3
+
+    D = depth[:, :, :, None, None]
+    # print(D.shape, Kinv[None, None, None, ...].shape, coord[:, :, :, :, None].shape )
+    pts3D_1 = D * Kinv[None, None, None, ...] @ coord[:, :, :, :, None]
+    # pts3D_1 live in your coordinate system. Convert them to Py3D's
+    pts3D_1 = M[None, None, None, ...] @ pts3D_1
+    # from reference to targe tviewpoint
+    pts3D_2 = R[None, None, None, ...] @ pts3D_1 + t[None, None, None, :, None]
+    # pts3D_2 = pts3D_1
+    # depth_2 = pts3D_2[:, :, :, 2, :]  # b,1,h,w
+    return pts3D_2[:, :, :, :3, 0][0]
+
+
+def create_triangles(h, w, mask=None):
+    """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