Module: Gsplat::Backend::RubyRasterizeToPixelsBackward

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

Overview

Tile orchestration for rasterization VJPs.

Class Method Summary collapse

Class Method Details

.backward(means2d, conics, colors, opacities, backgrounds, masks, width, height, tile_size, isect_offsets, flatten_ids, render_alphas, last_ids, grad_render_colors, grad_render_alphas, absgrad:) ⇒ Object

rubocop:disable Metrics/AbcSize, Metrics/ParameterLists



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# File 'lib/gsplat/backend/ruby/rasterize_to_pixels_backward.rb', line 10

def backward(means2d, conics, colors, opacities, backgrounds, masks, width, height,
             tile_size, isect_offsets, flatten_ids, render_alphas, last_ids,
             grad_render_colors, grad_render_alphas, absgrad:)
  # rubocop:enable Metrics/ParameterLists
  type = means2d.class
  color_gradient_shape = [means2d.shape[0], height, width, colors.shape[-1]]
  grad_render_colors = validate_gradient(type, grad_render_colors, color_gradient_shape)
  grad_render_alphas = validate_gradient(type, grad_render_alphas, [means2d.shape[0], height, width, 1])
  camera_count, gaussian_count = means2d.shape[0...2]
  total_gaussians = camera_count * gaussian_count
  grad_means = type.zeros(total_gaussians, 2)
  grad_conics = type.zeros(total_gaussians, 3)
  grad_colors = type.zeros(total_gaussians, colors.shape[-1])
  grad_opacities = type.zeros(total_gaussians)
  grad_backgrounds = backgrounds && type.zeros(*backgrounds.shape)
  grad_means_abs = absgrad ? type.zeros(total_gaussians, 2) : nil
  flattened = flatten_inputs(means2d, conics, colors, opacities)
  tile_height, tile_width = isect_offsets.shape[-2..]
  camera_count.times do |camera_index|
    tile_height.times do |tile_y|
      tile_width.times do |tile_x|
        backward_tile!(
          grad_means, grad_conics, grad_colors, grad_opacities, grad_backgrounds,
          *flattened, backgrounds, masks, isect_offsets, flatten_ids, render_alphas,
          last_ids, grad_render_colors, grad_render_alphas, camera_index, tile_x, tile_y,
          width, height, tile_size, grad_means_abs
        )
      end
    end
  end
  gradients = [
    grad_means.reshape(*means2d.shape),
    grad_conics.reshape(*conics.shape),
    grad_colors.reshape(*colors.shape),
    grad_opacities.reshape(*opacities.shape),
    grad_backgrounds
  ]
  [gradients, grad_means_abs&.reshape(*means2d.shape)]
end