This flyout provides a quick way to set a default tangent type for new animation keys created with Set Key Mode or Auto Key Mode. You can also access the tangent types from the Key Info (Basic) rollout and the Curve Editor's Key Tangency toolbar.
On each new set keyframe, the Key Tangent flyouts on the Key Info (Basic) rollout updates with the current default tangent type.
When you set a default tangent type, both the in and out tangents are set to match that type. If you set different in and out tangents via the Controller Defaults group of the Animation Preferences panel, the current flyout icon changes to a question mark.
Example: To set the default tangent type:
Position curves with Auto tangents
The curves are rounded at frame 10 but straighten out near frame 20. The interpolation transitions from Auto out tangents at frame 10 to Linear in tangents at frame 20.
The Position curves going from Auto to Linear tangents
The curve interpolations from frame 20 to 30 are straight lines because the keys' tangents are set to Linear.
The Position curves going from Auto to Linear to Linear tangents