Create a usdz box in ruby land

usdz.rb

USDZ_TEMPLATE = File.open('cube.usdz', 'rb').read

def generate_usdz(length, width, height)
  usdz = USDZ_TEMPLATE.dup

  # This is the block of bytes in the buffer that represent the vertex positions
  # They are stored as 32-bit floats
  buffer = usdz[1168,624].unpack("F*")

  buffer = resize_box_buffer(buffer, length, width, height)

  usdz[1168, 624] = buffer.pack("F*")

  usdz
end

# This function can be used by both the .glb and .usdz generation for modifying buffers.
# It takes in a buffer representing vertex data, and resizes the vertices based on specified dimensions
def resize_box_buffer(buffer, length, width, height)
  
  # Divide by two because of the symmetry of the cube. Ex: if the width is 3, then one side will be -1.5 and the other will be 1.5
  length *= 0.5
  width  *= 0.5
  height *= 0.5

  thickness = 0.01

  buffer.map { |element|
      sign = element<=>0
      if element.abs == 51
          sign * length 
      elsif element.abs == 52
          sign * height
      elsif element.abs == 53
          sign * width
      elsif element.abs == 41
          sign * (length - thickness)
      elsif element.abs == 42
          sign * (height - thickness)
      elsif element.abs == 43
          sign * (width - thickness)
      else
          element
      end
  }
end

# Example usage. You can use the output of this to save as a file or serve as a file
generate_usdz(1, 1, 4)