Task:

Load the Backpack Scan dataset from "backpack/data/backpack_512x512x373_uint16.raw", the information about this dataset:
Backpack Scan
Description: CT scan of a backpack filled with items.
Data Type: uint16
Data Byte Order: little Endian
Data Spacing: 0.9766x0.9766x1.25
Data Extent: 512x512x373
Data loading is very important, make sure you correctly load the dataset according to their features.

Visualize the backpack contents:
1. Apply volume rendering with different transfer functions for different materials
2. Create multiple isosurfaces for different density materials (metal, plastic, fabric)
3. Use distinct colors for different material types
4. Make the backpack exterior semi-transparent to reveal contents

Please think step by step and make sure to fulfill all the visualization goals mentioned above.

Finally, save the paraview state as "backpack/results/backpack.pvsm