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Fix look_at corner case

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Summary: When the camera is vertically oriented, calculating the look_at x-axis (also known as the "right" vector) does not succeed, resulting in the x-axis being placed at the origin. Adds a check to correctly calculate the x-axis if this case occurs.

Reviewed By: nikhilaravi, sbranson

Differential Revision: D23511859

fbshipit-source-id: ee5145cdbecdbe2f7c7d288588bd0899480cb327
This commit is contained in:
Amitav Baruah 2020-09-10 12:52:13 -07:00 committed by Facebook GitHub Bot
parent f8ea5906c0
commit eb517dd70b
2 changed files with 20 additions and 0 deletions
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6
pytorch3d/renderer/cameras.py
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@ -1226,6 +1226,12 @@ def look_at_rotation(
z_axis = F.normalize(at - camera_position, eps=1e-5)
x_axis = F.normalize(torch.cross(up, z_axis, dim=1), eps=1e-5)
y_axis = F.normalize(torch.cross(z_axis, x_axis, dim=1), eps=1e-5)
is_close = torch.isclose(x_axis, torch.tensor(0.0), atol=5e-3).all(
dim=1, keepdim=True
)
if is_close.any():
replacement = F.normalize(torch.cross(y_axis, z_axis, dim=1), eps=1e-5)
x_axis = torch.where(is_close, replacement, x_axis)
R = torch.cat((x_axis[:, None, :], y_axis[:, None, :], z_axis[:, None, :]), dim=1)
return R.transpose(1, 2)

14
tests/test_cameras.py
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@ -433,6 +433,20 @@ class TestCameraHelpers(TestCaseMixin, unittest.TestCase):
RT = get_world_to_view_transform(R=R, T=T)
self.assertTrue(isinstance(RT, Transform3d))
def test_look_at_view_transform_corner_case(self):
dist = 2.7
elev = 90
azim = 90
expected_position = torch.tensor([0.0, 2.7, 0.0], dtype=torch.float32).view(
1, 3
)
position = camera_position_from_spherical_angles(dist, elev, azim)
self.assertClose(position, expected_position, atol=2e-7)
R, _ = look_at_view_transform(eye=position)
x_axis = R[:, :, 0]
expected_x_axis = torch.tensor([0.0, 0.0, -1.0], dtype=torch.float32).view(1, 3)
self.assertClose(x_axis, expected_x_axis, atol=5e-3)
class TestCamerasCommon(TestCaseMixin, unittest.TestCase):
def test_view_transform_class_method(self):