The "Keys" menu of the "Curve Editor" provides several methods to continue a curve before the first or after the last animation key:
ZeroThe parameter's value is set to 0 before the first or after the last key to continue the curve.
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ConstantThis function uses the first or last key's parameter value to continue the curve.
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LoopThis function creates an endless repetition of the curve segment between the first and the last key to continue the curve.
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Loop OffsetThis function creates an endless repetition of the curve segment between the first and the last key to continue the curve: the values are added and the result is a growing or declining curve.
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Follow TangentThis feature uses the last key’s tangent gradient to continue the curve.
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