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I have and use brushes to do this, but for those who don't...here you go. Start with any image and make multiple duplicates.
You need to roll/rotate and change each one slightly different. This will take some time to get enough. The final image did not have enough for my liking, but you should get the point.
Here i made a new layer and used the random shape brush at 6 pixels and drew black as you see. You select one area with the wand, and with it still selected you you click on any of the 4 starting layers. Copy, and paste to a new layer. Use each layer for each of the 4 areas.
This is an option for each broken glass section to help sell the effect. Select the area and make a new layer. Fill that layer with a white and transparent gradient. If you do each section a little different, your outcome may be more realistic. Otherwise, you can ignore or come back to this.
Now you have each of your sections on layers. This is where i should have rolled each beginning image just a little more.
Each section needs some edge cleaning with AA's < no swearing >istant.
Now you select each layer and move them a bit. This makes the cracks vary is width.
Drop shadow with settings like this, or your own.
Do all sections with varying offset drop.
Cleanup each drop layer with another AA's as shown The bottom layer is the same image untouched and now seen through the crack.
Hit each layer with a light color or white as shown.
Before this final result you can darken the bottom layer, add dents, noise or or whatever you like. Now, you can also go back to the white gradient from a few images ago and add some reflection to each of the 4 areas. This will help sell the final result as more realistic if that's what you're going for. As always, change it up and have fun.