Module: Gsplat::Backend::RubySphericalHarmonics

Defined in:
lib/gsplat/backend/ruby/spherical_harmonics.rb

Overview

Numo forward/backward implementation of real spherical harmonics.

Class Method Summary collapse

Class Method Details

.backward(degree, directions, coefficients, grad_output, masks: nil, grad_dirs: true, grad_coeffs: true) ⇒ Object

rubocop:disable Metrics/ParameterLists



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# File 'lib/gsplat/backend/ruby/spherical_harmonics.rb', line 25

def backward(degree, directions, coefficients, grad_output, masks: nil, grad_dirs: true, grad_coeffs: true)
  # rubocop:enable Metrics/ParameterLists
  directions, coefficients, masks, leading_shape = validate_inputs(degree, directions, coefficients, masks)
  count = directions.size / 3
  basis_count = coefficients.shape[-2]
  channel_count = coefficients.shape[-1]
  gradient = directions.class.cast(grad_output)
  expected = leading_shape + [channel_count]
  unless gradient.shape == expected
    raise ShapeError, "expected output gradient #{expected.inspect}, got #{gradient.shape.inspect}"
  end

  normalized = normalize_directions(directions).reshape(count, 3)
  bases, derivatives = Math::SphericalHarmonicBasis.evaluate(normalized, degree, basis_count)
  apply_masks!(bases, derivatives, masks)
  gradient = gradient.reshape(count, channel_count)
  coefficient_values = coefficients.reshape(count, basis_count, channel_count)
  coefficient_gradient = if grad_coeffs
                           bases.reshape(count, basis_count, 1) * gradient.reshape(count, 1, channel_count)
                         end
  if grad_dirs
    direction_gradient = direction_gradient(
      directions,
      coefficient_values,
      gradient,
      derivatives,
      leading_shape
    )
  end
  [
    direction_gradient,
    coefficient_gradient&.reshape(*(leading_shape + [basis_count, channel_count]))
  ]
end

.forward(degree, directions, coefficients, masks: nil) ⇒ Object 



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# File 'lib/gsplat/backend/ruby/spherical_harmonics.rb', line 9

def forward(degree, directions, coefficients, masks: nil)
  directions, coefficients, masks, leading_shape = validate_inputs(degree, directions, coefficients, masks)
  count = directions.size / 3
  basis_count = coefficients.shape[-2]
  channel_count = coefficients.shape[-1]
  normalized = normalize_directions(directions).reshape(count, 3)
  bases, = Math::SphericalHarmonicBasis.evaluate(normalized, degree, basis_count)
  apply_masks!(bases, nil, masks)
  colors = (
    bases.reshape(count, basis_count, 1) *
    coefficients.reshape(count, basis_count, channel_count)
  ).sum(axis: 1)
  colors.reshape(*(leading_shape + [channel_count]))
end