What if the curves don't show up all the way, or don't show up at all?

The following situations have arisen

① Curve display is incomplete, or disappear once the curve is selected.

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Possible causes:

① Generally, it is because the graphics card is AMD graphics card.

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Solution:

Step1：

Find “Options” in “Tools” on the top menu bar. 

Step2：

① Find "OpenGL" in “View” on the left side.

②Uncheck the "GPU Tessellation".