Casting animation

Every time an unit uses a ability, it must go through it's Cast Animation in order to sucessfully cast it. The duration of the cast animation determines how fast an unit can cast abilities and recover from them. For example, a hero like Leshrac will have a hard time chaining his abilities because of his enourmous cast animation; in the other side, Invoker, having no cast animation at all, can chain abilities as fast as his cooldowns permit (and how fast can his player can press buttons). Cast animation is divided between Cast Point and Cast Backswing.

Cast Point
The cast point is the delay between when an ability command is issued, and the ability is actually performed. For example, if Death Prophet is issued to cast Crypt Swarm, she must first raise her hands in the air before the bats are summoned de facto, and this animation takes 0.5 seconds to do so. Therefore, it's said that she has a cast point of 0.5, and there will always be a delay of a half second before Death Prophet casts any ability.

An ability will only apply it's effect, enter cooldown and spend mana if it sucessfully reaches the casting point. For example, if Death Prophet starts casting something and she is disabled exactly at 0.49 of her cast animation, the ability won't happen but neither will it start cooling down or draw from the manapool. Conversely, if she's stunned exactly at 0.51, the ability will already have been sucessfully used, applying it's effects, entering cooldown and using mana. Because the casting animation can be interrupted by it's user by issuing another order (like the stop command), it's possible to cancel one's own ability even after it has been issued. There are many uses for this trick, like feinting or correcting a mistakenly aimed spell. Obviously, this can only be done with units with long cast point, since short cast points leaves not enough time to proper reaction. It worthy mentioning that the longer the cast point of a hero is, the easier it is to the opponent to react and even disable you before finishing your cast. For example, Rattletrap can easily prevent Earthshaker and Leshrac from casting their abilities with Battery Assault.

Channeling abilities must first be casted to start the channel, and then effect can be done. Once started, their mana costs and cooldowns are applied, even if the user interrupts the channel immediately. For example, Bane, having a 0.5 cast point, will not waste Fiend's Grasp if he gets stunned at 0.49 of his animation, but he will lose it if he gets stunned at 0.51 seconds.

No Cast Point
Certain abilities have no cast point (like Queen of Pain's Scream of Pain), and will be casted instantly regardless of the user's cast point. All items with active abilities are considered to have no casting time.

Delayed Cast Point
Other abilities have delayed cast point, meaning that these abilities will have the user's base cast time plus an arbitrary amount of casting to be sucessfully performed. For example, Sniper's Assassinate has a 1.7 delayed cast point. This means that Sniper, who was 0.3 cast point, will take 2 seconds to cast his ultimate. Other than having an extended casting, delayed cast point abilities do not differ at all from normal cast point abilities: Sniper will only spend fire the shoot, spend mana and send his ultimate into cooldown if he sucessfully casts for 2 seconds, and they can be canceled as usual. Delayed cast point must not be mistaken with channeling, the later requires continuous casting to keep the effect on, the former only needs a longer period of cast until it's effect occurs.

Cast Backswing
The cast backswing is the delay between a sucessfully finished cast point and when another queued command will be performed. For example, Warlock has 0.5 cast point and 0.5 cast swing. After issuing Shadow Word, it takes 0.5 seconds until the ability is actually used. After that, it takes another 0.5 seconds until Warlock proceds with his activities (like autoattacking the enemy hero). This totalizes a 1 second cast animation for Warlock. Unlike the cast point, the backswing is purely cosmetic and interrupting it has no negative effect whatsover (it can be interrupted in the same ways that he cast point can be). Because of this, the backswing can and should be canceled by immediately issuing another order, to be able to squeeze a few more actions in, with no drawbacks in doing so. This is mostly notably on Crystal Maiden and Keeper of the Light, since they have a small 0.3 cast point but a huge 2.4 backswing. Backswing cancel is an extremely important skill in serious Dota 2 play.

Delayed cast point abilities have backswing as usual. Channeling abilities have backswing as well, but they only happen when the channel is completed. Because often the channel is interrupted, either by enemy's crowd control or by user's input, it's rare having to deal with it. Most importantly, however, is that no cast point abilities also have backswing. These abilities allow fluid use, since they have no cast point and the backswing can be interrupted without problems, and thus is fundamental to perfect backswing cancelation on them to obtain the best results possible.

Items never have backswing.

List of abilities with no Cast Point
''Because all active items have no cast point, they will not be listed here. Instead, only unit abilities are going to be listed. Also, there are many heroes with 0 cast point (Dragon Knight, Ember Spirit, Goblin Techies, Invoker, Sand King and Venomancer), but only abilities that have no cast point themselves are going to be listed here.''