| “ |
|
„ | |
| — Duncan Geere[1] |
An observer is a block that emits a redstone signal when an adjacent block is updated.
Obtaining
An observer requires a pickaxe to be mined. When mined without a pickaxe, it will drop nothing.
| Block | Observer | |
|---|---|---|
| Hardness | 3 | |
| Tool | ||
| Breaking time[A] | ||
| Default | 15 | |
| Wooden | 2.25 | |
| Stone | 1.15 | |
| Iron | 0.75 | |
| Diamond | 0.6 | |
| Netherite | 0.5 | |
| Golden | 0.4 | |
- ↑ Times are for unenchanted tools as wielded by players with no status effects, measured in seconds. For more information, see Breaking § Speed.
Crafting
| Ingredients | Crafting recipe |
|---|---|
| Cobblestone + Redstone + Nether Quartz |
Usage
An observer is placed similarly to a piston, and will observe the block that it is placed against. The texture of the detecting side is that of an 'observing' face. As observers can detect the state of other observers, placing two adjacent observers, each watching the other, can make a fast and compact redstone clock.
Behavior
In Java Edition, an observer will detect changes in its target's block ID or data value, or the breaking or placing of a block (i.e. changes in its basic block state, but not its extended/actual block state). This means that changes like the age of crops will be detected, since they are part of the basic block state that is converted to metadata when the world is saved; however, changes such as the shape of a fence will not be detected, since those are part of the extended block state, which is not saved when the world is saved.
In Bedrock Edition, an observer acts as a block update detector, and detects anything that causes a block update in that edition.
Note that what causes a block update and how they propagate is very different between Java Edition and Bedrock Edition. As a result, each can detect some kinds of changes that the other can't. See the table below for a comparison.
When it detects something, the observer emits a redstone pulse of strong power at level 15 for 2 game ticks (1 redstone tick). The pulse can power redstone dust, a redstone comparator, a redstone repeaters, or any mechanism component located at its opposite end.
In the Java Edition, the pulse is emitted with a delay of 1 redstone tick. In Bedrock Edition, it is supposed to be delayed by 1 tick as well, but is actually delayed 2 redstone ticks due to MCPE-15793, a bug causing redstone delays to be incorrect when components are activated by world changes (which, in the case of the observer in MCPE, is the only way it can be activated), as opposed to pure redstone components ticking.
It also counts as a block change/block state change/block update when the observer itself is moved by a piston. When this happens, an observer emits a pulse after being pushed or pulled, but not beforehand.
Observers behave as a transparent block even though they block light. This means they cannot be powered by an external power source, nor power themselves with their own output.
Because observers in Java Edition detect changes in the basic block state, and not block updates, they can detect a wider range of phenomena than a block update detector (BUD) circuit in Java Edition can detect (as some block state changes don't cause block updates). However, they do not detect client-side blockstate changes that do not change the block data value, such as a fence reshaping or redstone dust rerouting. Observers in Bedrock Edition do detect block updates (but not block state changes), and so they detect the exact same things that any other BUD would detect in that edition.
Limitations
| Block state change: | Detected in Bedrock Edition | Detected in Java Edition | Detected in Legacy Console Edition |
|---|---|---|---|
| Locking / unlocking a redstone repeater | No | ||
| Changes to the data value of fire that signifies flammable surfaces surrounding fire | No | ||
| Changes in the shape of walls, fences, iron bars, glass panes, stairs, tripwire, redstone dust, vines, melon stem or pumpkin stem | No | ||
| A grass, mycelium, dirt, coarse dirt, or podzol block becoming snowy or not snowy | No | ||
| Changes to inventory of any blocks that comparators measure as containers | No | ||
| Activating / deactivating a beacon | No | ||
| Playing a note block | No | ||
| Opening and closing shulker boxes, chests & ender chests | No | ||
| Success of a command block | No | N/A | |
| Teleporting something by the end gateway | Yes | No | Yes |
| Adding / removing contents from a flower pot | Yes | No | Yes |
| The opening/closing of the top part of a door by hand, as opposed to by redstone power. | Yes | Yes | Yes |
| Powering / depowering of activator rails | Yes | Yes | Yes |
| Inverting / deinverting a daylight sensor | Yes | Yes | Yes |
| Activation of a dropper or dispenser | No | Yes | Yes |
| Activation / deactivation of redstone torch | Yes | Yes | Yes |
| Activation / deactivation of redstone ore | No | Yes | Yes |
| A piston (not the head) extending or contracting | Yes | Yes | Yes |
| Locking / unlocking a hopper | No | Yes | Yes |
| Spread of grass to dirt, or decay of grass into dirt | No | Yes | Yes |
| Growth of nether wart, forced growth of cocoa pods by bone meal, or growth of vines into empty space | Yes | Yes | Yes |
| Forced growth of sugar canes by bone meal | Yes | N/A | No |
| Aging of saplings, sugar canes or fire | No | Yes | Yes |
| Farmland going through its hydration stages | No | Yes | Yes |
| Moving potions and other items to / from a brewing stand | No | Yes | Yes |
| Activation / deactivation of a dragon head | Yes | No | Yes |
| Placing / removing an item frame, adding / rotating / removing an item in an item frame | Yes | No | Yes |
| All other block / block state changes | Yes | ||
Data values
Block data
| Bits | Values |
|---|---|
| 0x1 0x2 0x4 |
Three bits storing a value from 0 to 5:
|
| 0x8 | If set, the observer is powered. |
Block state
| Name | Default value | Allowed values | Description |
|---|---|---|---|
| facing | south | downeastnorthsouthupwest | The direction the observer is observing. The same direction the player faces when placing the block. |
| powered | false | falsetrue | True while the observer is observing a change and emitting a pulse. |
| Name | Metadata Bits | Default value | Allowed values | Values for Metadata Bits |
Description |
|---|---|---|---|---|---|
| facing_direction (Hidden) | 0x10x20x4 | 0 | 012345 | 012345 | The direction the observer is observing.
|
| minecraft:facing_direction | Not Supported | down | downeastnorthsouthupwest | Unsupported | The direction the observer is observing. |
| powered_bit | 0x8 | false | falsetrue | 01 | True while the observer is observing a change and emitting a pulse. |
History
| release | |||||
|---|---|---|---|---|---|
| 1.11 | 16w39a | Added observer block. When first added, the observers acted as a block update detector, and would emit pulses that lasted 1 game tick (0.5 redstone ticks) and had a signal strength of 1. The observer could also power blocks (like a repeater). It also had no delay between detecting a block update and emitting a pulse, meaning that observers were essentially instant. They were also placed with the observing, or input, side facing the player. | |||
| File:Observer 16w39a.png Note: the "arrow" texture on the top/bottom of the observer was pointing the wrong direction (towards the input, rather than the output). This was not noticed by most people, though, since the observer in Pocket Edition had a texture bug where the top & side textures would not rotate properly (except the output/input sides), causing the arrow texture to always point in the same direction. | |||||
| 16w41a | Observers were changed to emit 4 game tick (2 redstone tick) pulses[2], and their signal strength was changed to 15.[3][4] | ||||
| Observers *appear* to no longer strongly power blocks, and now only emit activation power, like a block of redstone. (And this may have been the intended behavior for this snapshot.) However, in reality, they still strongly power blocks, but the blocks adjacent to those blocks aren't given block updates, causing weird and buggy behavior.[5] | |||||
| Observers are now placed with the output facing the player.[6][7] | |||||
| Fixed a bug where observers would redirect redstone dust from all 4 directions.[8] (They are only supposed to redirect dust from their output side.) | |||||
| 16w42a | The devs attempted to make observers no longer detect block updates happening to air blocks, in order to make observer behavior more predictable.[9] In the process they broke redstone mechanics a bit, so that the block update bug from the previous snapshot now affected repeaters & comparators, too.[10] | ||||
| 16w43a | File:Observer 16w43a.png Fixed the rotation of the "arrow" texture so it would point in the right direction. | ||||
| General redstone mechanics work as they did before 16w42a, with the exception of the change named below. | |||||
| Observers now output strong power like in 16w39a, except that they, as well as repeaters & comparators, no longer provide block updates to transparent blocks or air. | |||||
| 16w44a | The block update changes relating to redstone from 16w42a & 16w43a were fully reverted. | ||||
| Observer behavior was overhauled/redefined. The observer changed from a block update detector to a block state change detector. Observers were changed to detect when the block it was observing changed, its basic block state changed, or the block was placed/destroyed. (Note that it does not detect changes in the extended block state, AKA changes that are not saved when the world is unloaded, such as the shape of a fence, or whether or not a repeater is locked.) This change made observer behavior much more predictable, as unexpected/invisible block updates would no longer trigger observers.[11] | |||||
| Observers were changed to emit a 2 game tick (1 redstone tick) pulse when activated.[12] | |||||
| Observers no longer output power instantly.[13] | |||||
| 1.11-pre1 | |||||
| The redstone output side now blinks red when it outputs power. | |||||
| Pocket Edition Alpha | |||||
| 0.15.0 | May 2, 2016 | Jeb tweeted that Daniel Wustenhoff is a working on a BUD block.[14] | |||
| Tommaso Checchi tweeted his "rejected graphics" for the block.[15] | |||||
| build 1 | File:Observer PE.png Added observer block. | ||||
| 0.15.3 | Observers are now placed like a piston and not a log. | ||||
| Bedrock Edition | |||||
| 1.2 | build 1 | File:Observer BE.png Updated textures to match Java Edition. | |||
| Observer blocks can now detect many more block changes. | |||||
| Increased the strength of the redstone pulse outputted by Observer blocks and they no longer pulse twice when observing a retracting piston. | |||||
| Opening and closing the command block screen will no longer activate an observer block | |||||
| Legacy Console Edition | |||||
| TU54 | CU44 | 1.52 | Patch 24 | Patch 4 | Added observers. |
Issues
Issues relating to "Observer" are maintained on the bug tracker. Report issues there.
Trivia
- When moved by a piston, an observer sends a 2 game tick (1 redstone tick) pulse after being moved, which makes it useful for slime block flying machines.
- The current Observer texture was created because Jeb kept confusing which side was front/back. He said it was inspired by the "rejected texture" created by Tommaso Checchi.[16][17]
Gallery
See also
References
- ↑ "Block of the Week: Observer" – Minecraft.net, November 10, 2017
- ↑ https://bugs.mojang.com/browse/MC-107410
- ↑ https://bugs.mojang.com/browse/MC-107783
- ↑ https://bugs.mojang.com/browse/MCPE-17439
- ↑ https://bugs.mojang.com/browse/MC-108696
- ↑ https://bugs.mojang.com/browse/MC-107934
- ↑ https://bugs.mojang.com/browse/MCPE-17321
- ↑ https://bugs.mojang.com/browse/MC-107795
- ↑ https://bugs.mojang.com/browse/MC-107730
- ↑ https://bugs.mojang.com/browse/MC-108897
- ↑ https://bugs.mojang.com/browse/MC-107760
- ↑ https://bugs.mojang.com/browse/MC-108697
- ↑ https://bugs.mojang.com/browse/MC-107623
- ↑ "Hype train! @darngeek is working on a device that will act as a proper BUD block in MC:PE (PC eventually), currently called "Observer"" – @jeb_ (Jens Bergensten) on X, May 2, 2016
- ↑ "Here's my rejected graphics for the Observer, because @darngeek has no artistic sensibility" – @_tomcc (Tommaso Checchi) on X, May 2, 2016
- ↑ https://twitter.com/jeb_/status/795625080067866624
- ↑ "Here's my rejected graphics for the Observer, because @darngeek has no artistic sensibility" – @_tomcc (Tommaso Checchi) on X, May 2, 2016
