Tracing with the smart manual mode(3D)

Before you start

Open an image stack or single images.
Make image adjustments as necessary.
Open the 3D Visualization window.
If you're using the 3D Volume view, select Partial projection under Image stack settings in the Image Display panel.

Click the Vessel button to display the Trace Vessels panel and select Smart manual.
Check Snap cursor to tracing so that you can easily connect two segments while tracing or resume tracing later (potential connecting points will be displayed as wireframe spheres or rings).
Check Pan to window after each click so that the program re-centers each point outside the field of view automatically.
Place the cursor over the vessel and adjust the cursor diameter to match the diameter of the vessel at that point: Hold down Ctrl and scroll the mouse wheel.
Click to place the first point.
Place the cursor over the next point, adjust the cursor diameter, and click to place the next point.
Move the partial projection sliders as needed to reveal more of the vessels and continue tracing.
When you want to end the vessel or connect to another segment, click to place the last point then right-click and select Ending.

Place the cursor over the vessel until you see a potential connecting point (signaled by a wireframe sphere or ring).
Click and continue tracing.

Use Ctrl-Z to undo your last click.