Časování animací
*Relativní vs absolutní
*From-To, To, By, From-By
*Aktivace více animací najednou kompozicí (i na jedné vlastnosti)
*Zrychlení/zpomalení vyvolává přirozený vzhled
*Není-li určeno, rychlost je lineární
Numerical animations provide From, To, and By properties. If you specify From and To, this indicates the absolute start and end values of the animation. The previous value of the relevant property will be ignored in this case.

If you just specify To, the animation will animate from the property’s current value to the target specified by To.

If you specify just By, the animation is relative – it will start from the property’s current value and add the value specified in By to form the target value. (Not all animation types have a By property – only types for which addition is defined support this. ColorAnimation does not, for example.)

If you specify From and By, this indicates an absolute start position and a relative target position.

You might have multiple animations applied to the same property. This is useful for multi-stage animations. If you use the By property, each animation applies from where the previous one left off. If animations overlap, then if the second is a By animation, it will simply be added to the first one.

If an animation specifying From overlaps in time with another animation for the same property, the later of the two overrides the earlier one.
By default, animations perform linear interpolation – they change the animated property at a constant rate over the duration of the animation. This can result in a rather unrealistic feel for certain kinds of animations.

Animation timelines therefore support a soft start and/or finish to the animation. By specifying an AccelerationRatio, you can make the animation gradually ramp up to speed. This property indicates the proportion of the total duration that should be spent accelerating. For example, if you specify a value of 0.3, the animation will start at zero speed, and will ramp up to full speed over the first 30% of the duration. (The appropriate value for ‘full speed’ is calculated automatically.) You can also specify a DecelerationRatio, which indicates the proportion of the total time that should be spent slowing down to a halt at the end of the animation.

Obviously the sum total of these two properties must be less than or equal to one: you cannot spend more than 100% of the time speeding up and slowing down!
All timelines have a RepeatBehavior property which indicates whether the timeline should repeat, and if so for how long. A value of Forever means it should repeat indefinitely. (However, if the timeline is a child of a timeline with a specific finite duration, ‘Forever’ really just means ‘Until the parent timeline ends’.) You can specific finite repetition either by indicating how long the timeline should repeat for, or the number of repetitions. Note that in both cases this includes the first run through, so a RepeatBehavior of “1x” is effectively the default. Likewise, if you make the RepeatBehavior a duration that is the same as the animation’s behavior, this also lets the animation run just once.

All timelines also have an AutoReverse property. If this is set to true, the timeline will run in reverse once it reaches the end. This doubles the effective duration of the timeline.