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Clicking any of the other letters will change the viewport to a 3D perspective or an orthographic view:
- 3D change to a 3D perspective view; by default it will show the last active perspective in that window.
- T for top orthographic view.
- D for bottom orthographic view.
- L for left orthographic view.
- R for right orthographic view.
- F for front orthographic view.
- B for back orthographic view.
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