Time.fixedUnscaledDeltaTime

マニュアルに切り替える
public static float fixedUnscaledDeltaTime ;

説明

The timeScale-independent interval in seconds from the last fixed frame to the current one (Read Only).

For reading the unscaled delta time it is recommended to use Time.unscaledDeltaTime instead because it automatically returns the right unscaled delta time if you are inside a FixedUpdate function or Update function.

Unlike fixedDeltaTime this value is not affected by timeScale.