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nerfstudio/tests/utils/test_math.py
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2025-01-18 20:15:12 -08:00

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Python

import numpy as np
import pytest
import torch
from scipy.spatial.transform import Rotation as ScR
from nerfstudio.utils.math import components_from_spherical_harmonics, rotate_spherical_harmonics
@pytest.mark.parametrize("components", list(range(1, 5 + 1)))
def test_spherical_harmonics(components):
torch.manual_seed(0)
N = 1000000
dx = torch.normal(0, 1, size=(N, 3))
dx = dx / torch.linalg.norm(dx, dim=-1, keepdim=True)
sh = components_from_spherical_harmonics(components, dx)
matrix = (sh.T @ sh) / N * 4 * torch.pi
torch.testing.assert_close(matrix, torch.eye(components**2), rtol=0, atol=1.5e-2)
@pytest.mark.parametrize("sh_degree", list(range(0, 4)))
def test_rotate_spherical_harmonics(sh_degree):
torch.manual_seed(0)
np.random.seed(0)
num_coeffs = (sh_degree + 1)**2
coeffs = torch.rand(1000, 3, num_coeffs)
# Norm Preservation
rot_matrix = ScR.random().as_matrix()
rotated_coeffs = rotate_spherical_harmonics(coeffs, rot_matrix)
norm_original = torch.norm(coeffs, dim=-1)
norm_rotated = torch.norm(rotated_coeffs, dim=-1)
torch.testing.assert_close(norm_original, norm_rotated, rtol=0, atol=1e-6)
# 0th order coeffs are invariant to rotation
torch.testing.assert_close(coeffs[..., 0], rotated_coeffs[..., 0], rtol=0, atol=1e-6)
# 1st order coeffs undergo simple rotation
if sh_degree > 0:
torch.testing.assert_close(rot_matrix @ coeffs[..., 1:4], rotated_coeffs[..., 1:4], rtol=0, atol=1e-6)
# Identity Rotation
rot_matrix = np.eye(3)
rotated_coeffs = rotate_spherical_harmonics(coeffs, rot_matrix)
torch.testing.assert_close(coeffs, rotated_coeffs, rtol=0, atol=1e-6)