ETT Rules

ETT rules are designed to approximate real ITTF (International Table Tennis Federation) rules for competition games.

## Basic rules

These rules are what unranked multiplayer games are governed by. These are similar to the full ITTF rules, with the exception that there is no restriction on the how the ball must thrown before service (2.6.2 in the ITTF handbook) or in which part of the throw the ball must be struck (2.6.3 in the ITTF handbook "as the ball is falling") .

## Ranked rules

These rules govern ranked multiplayer games. Rule 2.6.2 (which is ignored in the basic rules) is partly adhered to in these rules: the ball must be thrown 16cms (about the height of the net) vertically, must be "near vertical" (tolerance in-game is 22° in any direction) and must be allowed to start to fall before striking (2.6.3).

## Reason for lost points

When a player loses a point, the reason will be displayed on the TV screen along with the score in each environment:

* toss was too forward
* toss was under the table **(ranked only)**
* toss was too low **(ranked only)**
* toss was too angled **(ranked only)**
* service hit was under the table **(ranked only)**
* service hit was while ball was rising **(ranked only)**
* service hit was too far forward
* did not hit near side of table after your service hit
* did not hit far side of the table after service hit
* hit out of turn
* did not hit the ball after it bounced on the table
* did not hit the far side of the table

"Toss was too low" and "Toss was too angled" are currently given a warning instead of an instant fault, if they are the only rules broken, and only on the second infraction will they result in a lost point. This is because they are relatively new rules in ETT, so to give players who are not used to them a chance to adapt.

## Rule Differences between ITTF and ETT

Ignoring that the basic rules are more lenient, not every ITTF rule is implemented into ranked ETT rules:

### Potential future ETT rule changes

* There is no current restriction on the distance the service throw can move laterally. This may change in future.
* While there is a restriction on the angle that the ball toss can deviate from vertical, it is more lenient than in ITTF practice. 22° tolerance means the ball can move 1.6 times as far laterally than the height it reached when it falls again to the height it was thrown from. The exact amount of angle tolerance may be revisited.
* Since ETT can be sure about whether a ball was landing out or in, there is no need for rules stating when it is acceptable to catch or touch the ball which was assumed to be going out. These rules exist so that umpires don't have to make a judgment call, but the program knows for sure whether a ball was landing in or out, and may in future implement that ability when a ball is touched before landing.
* "Toss was too low" and "Toss was too angled" are currently given a warning instead of an instant fault, if they are the only rules broken, and only on the second infraction will they result in a lost point. This is because they are relatively new rules in ETT, so to give players who are not used to them a chance to adapt. This may change when players are more used to it, as the amount of warnings is far more than ITTF rules would allow.
	+ Though the amount of warnings is greater than ITTF would allow, they do give leeway for umpires to give a warning instead of fault for "close call" serves which are not blatantly illegal, only technically. ETT may change to resemble this.
	+ The current warning system is bugged, unintentionally giving people an extra chance with serves which break other, long-established rules, when they also break the new ones. This will be fixed.

### Irrelevant rules

* As no hand is rendered and the ball is thrown without any method of imparting spin, the requirement to have a flat palm and not to impart spin on the throw before service are ignored.
* Rules outlawing hiding service point of contact with the body are irrelevant, since a body is not rendered. However, it is currently possible to obscure point of contact using the headset or controller.
* You are not permitted to deliberately make sound to distract your opponent in real games, but an option to mute your opponent while a point is in progress is planned, and you can choose to mute opponents completely in any case.

### Discarded rule for service toss

In ITTF rules, you are not allowed to abort a service toss and are awarded a fault. There is no penalty for this in ETT, as there are various factors difficult to account for:

* Many players like to bounce the ball on the floor or the table before service and this is hard to differentiate from a ball toss
* A courteous player may notice in the middle of their ball toss that their opponent is not ready to receive
* Some players have reported issues with unintended high ball tosses resulting from tracking anomalies
* Some real-life players find it harder to emulate their ball toss in ETT with a controller than with their open hand

As such this rule is not likely to be implemented, although a fault for a near miss of the ball on service may be considered in future.

### VR-specific rules

Due to the nature of playing table tennis without the limitations of a physical table, some players have gotten used to being able to pass the bat through the table. This allows some players to do stronger swings at short balls that in real life would require a "flick" shot, and thereby gain an advantage. Without the point loss, pain and potential damage to bat and hand, players have no reason to learn otherwise unless they wish to be authentic or try real table tennis.

As such, simple table-bat physics will be added where swinging the bat through the table will make the bat get stuck on the original side temporarily, and the bat leaning into the table will make it deflect off it at an angle.

## Common misunderstandings of rules

There are many popular "house rules" which are believed to be actual table tennis rules. If you wish to play a game with rules such as these, you have to do it in free hit and self-referee:

* The beginner serve (where you bounce the ball with your hand on your side of the table before hitting the ball directly to your opponent's side of the table) is not legal, and you have to hit the ball above and behind the baseline on serve, make the ball bounce once on your side and then at least once on your opponent's side of the table.
* There is no need to serve diagonally as is often believed. This applies only to doubles in ITTF rules, where the ball must be served with the first bounce on the near right side and the second on the far left side.
* A serve that bounces once on your side and then twice on your opponent's side is not a fault. In fact, this is usually the aim for serves by professional players.
* Volleys (hitting the ball before it has bounced on your side) are not legal in table tennis and result in a lost point.
* If the ball strikes the edge or corner of the table, that is legal and the rally continues, but if it hits the side of the table without touching any part of the edge or corner, that is not legal and results in point loss.
* You are permitted to move to the other side of the table to hit a shot the has spun backwards back over the net. Of course, most people do not prioritise this area when setting up their playspace, so this usually ends up being impossible in VR anyway.
* There is no limit to the amount of times you can serve brushing the net but with the ball still landing in. You will receive a let each time and replay.
* The net for rules' purposes includes every part of the structure, including the posts and clamps. Except on serve as above, hitting the net is a completely neutral event at any point of the ball's flight.
	+ An unintuitive consequence is that extreme backspin shot or serve that starts going backwards after going over the net, and hits the net going the other way may still be hit by the receiver, the point is still active despite the ball hitting something between bounce and bat.