Vision

[Lordshinjo]

Vision

This is a guide about vision in Warcraft III and DotA in particular, and it has nothing to do with Pacman.

Or does it ?

The DotA section of this guide is up to date with the 6.73c version.

• Introduction
• General Concepts
• DotA Specifics
• X

If you've ever started a game in Warcraft III, using any map, you'll have remarked this : you can see stuff. This is the basis of this game, if you didn't see anything, you simply couldn't play.
You'll also have realized that some heroes/units see farther than others, depending on whether it's night or day, and that you usually can't see past a tree.

The goal of the first section is to explain what vision is in Warcraft III, and how it works, in greater details.
The second section shows some particular cases of vision in DotA.

• Map Grid
• Fog Update Time
• Sight Radius
• Day and Night
• Dying Units
• Occlusion
• Height
• Flying Units
• Fog Modifiers
  

To understand how vision works, the most important thing to understand is that a map is composed of a big grid.
Every square in this grid is called Cell, its dimensions are 128x128 (in Warcraft III distance units).

The fog of war is updated every 0.4s since the start of the map.

This means that every 0.4s, the position of every unit, their sight range, and any sight that should be blocked or not are computed.
Then, the fogged or visible status of each grid cell is decided for each player.

You can then see a visual delay when the fog goes away or comes back on some cells, but this is only visual : as soon as the fog of war begins to appear or disappear, the vision has already been completely lost or gained on a particular zone.

Whether a unit is visible or not can however be changed outside of this update time, as a unit leaving a visible cell for a fogged cell will immediately cause this unit to be fogged, without waiting for the next update.

Every unit in Warcraft III has 2 fields defining how far it can see : one for the day, and one for the night. These values are capped at 1800.

But these values aren't directly used.
Instead, they can be classified in 15 different Sight Levels, defining how many cells away the unit can see.

Sight level	Min. sight radius	Max. sight radius	Picture		Sight level	Min. sight radius	Max. sight radius	Picture
0	0	63	None		8	960	1087
1	64	191			9	1088	1215
2	192	319			10	1216	1343
3	320	447			11	1344	1471
4	448	575			12	1472	1599
5	576	703			13	1600	1727
6	704	831			14	1728	1800
7	832	959

Every unit having a day field and a night field, you can easily understand that its vision differ depending on whether it is night or day.

But a particular case is the transition between day and night : this is the only moment when a unit's sight radius can be different from these 2 values, as the game makes it transition smoothly from one value to the other.
This transition usually lasts 3.2s (less when the transition lasts 1 or 2 levels), with the vision gaining 1 or 2 levels of sight range at short intervals of time, usually 0.4s. (and more generally always a multiple of 0.2s)

The most usual transition for heroes, from 800 (level 6) to 1800 (level 14), is the perfect example, as the unit gains 1 sight level every 0.4s during 3.2s.
This particular transition is also symmetrical, as it is exactly the same from 1800 to 800, even though this is usually not the case.

A dying unit still has vision during a time equal to its death time, but its sight range is capped by the Gameplay Constant "Fog Reveal Radius - Dying Unit".
In DotA, this constant is set to 500. This means that units with more than 500 sight range will have their sight range reduced to 500 (level 4) while dying. Units with less than 500 will not have their vision changed at all.

Note that due to an engine bug, only units having gone through at least one day->night (or night->day) transition will have their vision reduced this way.

Some objects, like trees or cliffs, can block vision.
These objects are called Occluders.

An occluder must cover the bottom right corner of a cell to be considered as covering the entire cell.

The first thing to know how vision is blocked is how the unit is placed around the blocker. There are 4 possibilities :

Position	Occlusion mask
In a straight line
In a diagonal line
Between a straight and a diagonal line
On the same cell

When surrounded by multiple occluders, the resulting occlusion mask is the superposition of the occlusion masks of each occluder.
The minimum number of vision blockers to completely block a unit's vision is 8, one in each cell around the unit.

You surely know that sometimes, being higher than a tree can make your vision go over it.
This is because all trees have an Occluder Height.
This value is usually 230 for a tree of medium size (called Tree Wall in World Editor), and 300 for a bigger tree (called Canopy Tree).
But like sight range, these exact values aren't used. Instead, they are converted in Cliff Levels.
A cliff level corresponds to 128 height, but also to the height of a cliff.

Cliff level	Min. height	Max. height
0	0	0
1	1	128
2	129	256
3	257	384
4	385	512
...	...	...

With their 230 occluder height, medium trees can be said to be occluder level 2. This means that you need to be at least on a cliff level 2 to see over them.

In this example, the north tree is level 3, the west tree level 2, and the unit is placed on a cliff level 2 :

Note that a unit can change height only by going on a cliff, or an elevated object (like a platform).
The "Apply Height" tool in World Editor, used to create smooth hills, will not change the height of the terrain.

When going up a ramp, the cliff level increases at a particular point : the middle of the second cell.

For the purpose of determining whether a unit's vision is blocked or not, flying units can be considered as being always at an infinite cliff level.
This means that their vision can never be blocked by anything.

Some spells can create Fog Modifiers, via the CreateFogModifierRadius function.
Some hardcoded spells, Mirror Image and Storm, Earth and Fire (more known as Primal Split in DotA), also create a fog modifier.
For Mirror Image, the radius is specified by the area of effect field (this field has no other purpose), and the fog modifier is destroyed when the unit casting Mirror Image appears.
Storm, Earth and Fire creates fog modifier with a radius equal to the casting unit's sight range, and the fog modifier is destroyed after 3s.

These fog modifiers have a center and a radius, but as before, the radius isn't directly used, it is instead converted into a size, each size corresponding to the approximate radius in cells.
Fog modifiers obviously ignore any occluders.

Fog modifier size	Min. radius	Max. radius	Result		Fog modifier size	Min. radius	Max. radius	Result
0	0	127	Nothing		5	640	767
1	128	255			6	768	895
2	256	383			7	896	1023
3	384	511			8	1024	1151
4	512	639			...	...	...	...

There is a second way for fog modifiers to be created : whenever a unit is attacked or targeted by a spell of a second unit, a fog modifier is created around the second unit.
This fog modifier has a radius equal to the "Fog Reveal Radius - Attacking Unit" Gameplay Constant, and it will disappear either after a number of seconds equal to "Decay Time (Sec) - Fog of War Flash", or when the second unit creates another fog modifier this way.

• Hero Vision
• Spells Providing Vision
• Roshan Area
  

Most heroes in Dota have a 1800/800 vision (which is short for 1800 sight range during the day and 800 during the night).

The following heroes have a different vision :

• Night Stalker: 1200/1800
• Tormented Soul: 1800/900
• Bounty Hunter: 1800/1000
• Sniper: 1800/1000
• Faerie Dragon: 1800/1200
• Priestess of the Moon: 1800/1200
• Treant Protector: 1800/1200
• Ancient Apparition: 1800/1400
• Alchemist: 1800/1400
• Drow Ranger: 1800/1700
• Enchantress: 1800/1800
• Geomancer: 1800/1800
• Nightcrawler: 1800/1800
• Lycanthrope (under Lycanthropy): 1800/1800
• Moon Rider (with Lunar Blessing): 1800/1800

The visions of other units in DotA are listed there.

Some spells in DotA provide vision where they are cast.
The mechanics behind this vision can be of multiple origin.

The first and most common source of vision is a unit.
This unit is created either to cast a spell, or to exist as a visual.
The unit is very often flying, so the vision it provides is unobstructed, but it happens that some spells create ground units.
For some of these spells, the unit stays at a fixed position during its death. (this is the red duration in the table)
Short list of examples : Mirana's arrow, Wave of Terror.

The second source of vision is a fog modifier, centered on where the spell was cast, and with a radius specified in the spell. (through triggered or hardcoded means)
Short list of examples : Sticky Napalm, Mirror Image.

Another source of vision is the Faerie Fire spell: this spell gives you the vision of the affected unit, and allows to see it even if it is invisible.
Track and Amplify Damage are directly based on Faerie Fire.

The last one is done by giving a unit's vision to a player.
This allows this player to see what the unit sees
If the unit turns invisible, it will still be invisible to the player, but units will still be able to attack it (even though you can't directly click on it).

Here is the entire list of spells creating vision, with the type of vision they provide :

Skill	Type	Radius	Location	Duration	Note
Torrent	Fog modifier	400	Torrent	4s
X Marks the Spot	Flying	1000/1000	X	5.94s
Ghost Ship	Flying	800/800	Boat	Boat travel (3s) + 3.34s
Wild Axes	Ground	500/500	Axes	Axes travel
Primal Split	Fog modifier	1800/800	Panda's location	3s
Storm Bolt	Flying	800/800	Projectile	Projectile travel + 3.34s
Echo Stomp	Flying	600/600	Spirit, if he's not already summoned	Channeling duration
Ancestral Spirit	Flying	600/600	Spirit	While the Spirit exists
Earth Splitter	Fog modifier	500	Every 200 distance along the split	4s each
Overgrowth	Flying	350/350	Position of every affected unit	Flash
Spirits	Flying	400/400	Spirits	While the Spirit orbits, then 3.34s after explosion
Relocate	Fog modifier	500	Io's original location	Until the end of the spell or Io's death
Unstable Concoction	Flying	400/400	Projectile	Projectile travel + 3.34s
Power Cog	Ground	1600/600	Cogs	Spell duration + 3s
Rocket Flare (1)	Flying	450/450	Rocket	Rocket travel
Rocket Flare (2)	Fog modifier	600	Impact	10s
Hookshot (1)	Flying	100/100	Regular hook link	Duration of the link
Hookshot (2)	Flying	450/450	Last hook link	Duration of the link
Fire Spirits	Flying	300/300	Spirit	While the Spirit exists
Sun Ray (1)	Fog modifier	225	Every 150 distance along the ray	2s, created every 0.2s
Sun Ray (2)	Fog modifier	500	Phoenix's position	For 2s after being damage by Sun Ray	Given to the enemy
Supernova	Flying	450/450	Sun	Sun duration + 3.34s
Ice Shards	Flying	800/800	Projectile	Projectile travel
Snowball	Flying	800/800	Snowball	Snowball travel + 3.34s
Timber Chain (1)	Flying	100/100	Regular hook link	Duration of the link
Timber Chain (2)	Flying	450/450	Last hook link	Duration of the link
Chakram	Flying	800/800	Chakram	Duration of the spell + 3.34s
Phantasm	Fog modifier	1000	CK's location	Around 0.63s (0.5s + illusion projectile travel)
Infest	Shared vision	N/A	Infested unit	Until the end of the spell
Night Stalker with Aghanim's	Flying	0/1800	NS's position	As long as NS has Aghanim
Pit of Malice	Fog modifier	800	Center of the pit	7s
Meat Hook	Flying	500/500	Position of hooked enemy	4s when an enemy is hooked
Amplify Damage	Faerie Fire	N/A	Target	Spell duration
Charge of Darkness	Flying	400/400	Target's position	Charge duration + 0.94s
Sand Storm	Ground	1000/750	4 units offset by (-150,-150), (-150,150), (150,-150), (150,150) to SK	Spell duration
Assassinate	Shared vision	N/A	Target	Until Sniper stops casting the spell
Waveform	Flying	1000/1000	Morphling's position	Travel time
Mirror Image (Naga Siren)	Fog modifier	1000	Naga's position	Around 0.43s (0.3s + illusion projectile travel)
Spirit Lance	Flying	800/800	Projectile	Projectile travel + 3.34s
Elune's Arrow	Flying	800/800	Projectile	Projectile travel + 3.34s
Whirling Axes (ranged)	Flying	500/500	Axes	Axes travel (0.6s) + 3s
Whirling Axes (melee)	Flying	500/500	Axes	Axes travel (3s) + 3s
Homing Missile (1)	Flying	500/500	Missile	Missile travel + 3.34s
Homing Missile (2)	Shared vision	N/A	Missile	From 1 second after the missile starts moving	Given to the enemy
Call Down	Fog modifier	350	Center of the target area	4s
Wave of Terror	Flying	500/500	Every 400 distance along the wave	3s each
Track	Faerie Fire	N/A	Target	Spell duration
Sleight of Fist	Fog modifier	600	Center of the target area	Spell duration
Fire Remnant	Ground	450/450	Fire remnant	Remnant duration + 0.1s
Strygwyr's Thirst (1)	Shared vision	N/A	Non invisible heroes under 40% HP inside the AoE	As long as they have under 40% HP and are not invisible
Strygwyr's Thirst (2)	Faerie Fire	N/A	Heroes under 20% HP inside the AoE	As long as they have under 20% HP
Stifling Dagger	Flying	600/600	Projectile	Projectile travel + 3.34s
Requiem of Souls (1)	Ground	1000/750	SF's position	5s	These are units casting Carrion Swarm
Requiem of Souls (2)	Ground	1000/750	On each unit in a 700 AoE around SF	5s	These are units casting Cripple
Sunder	Flying	1800/1800	Position of TB and target	3.2s	Vision on TB is given to TB, vision on target is given to target
Spectral Dagger	Flying	500/500	Each shadow of the shadow path	15s
Venomous Gale	Flying	800/800	Projectile	Projectile travel (0.7s)
Earthbind	Flying	800/800	Projectile	Projectile travel + 3.34s
Plasma Field	Flying	800/800	Razor's position	Spell duration (2.4s) + 3.34s
Static Link	Flying	800/800	End of the link (not on Razor's side)	Spell duration + 3.34s
Chronosphere	Flying	1000/1000	Center of Chronosphere	Spell duration
Mystic Snake	Flying	800/800	Projectile	Projectile travel + 3.34s
Crystal Nova	Ground	1000/750	Center of the target area	5s
Dream Coil	Flying	1000/1000	Coil	Spell duration (5/7s)
Illusory Orb	Flying	800/800	Projectile	Projectile travel + 3.34s
Illuminate	Flying	350/350	1 unit created every 0.5s every 100 distance while Ezalor is channeling	10.34s each
Lightning Bolt	Flying	1000/1000	Target's position	6s	This is a unit casting Chain Lightning
Thundergod's Wrath	Flying	1000/1000	Position of each target	6s	Same
Sprout	Fog modifier	1000	Center of the target area	Spell duration
Static Remnant	Flying	800/800	Static remnant	Spell duration
Ball Lightning	Flying	1000/1000	Position of Storm	Travel time
Shackleshot	Flying	800/800	Projectile	Projectile travel + 3.34s
Powershot	Flying	800/800	Projectile	Projectile travel + 3.34s
Thunder Strike	Flying	450/450	Target's position	Spell duration (4s) + 3s
Glimpse	Flying	400/400	Projectile	Projectile travel + 3.34s
Kinetic Field	Fog modifier	300	Center of the target area	5.5s
Static Storm	Flying	450/450	Center of the target area	Spell duration (5s)
Ice Path	Ground	200/200	1 ice block created every 0.05s every 100 distance	3.5s each
Arcane Bolt	Flying	325/325	Projectile	Projectile travel + 3.34s
Concussive Shot	Flying	400/400	Projectile	Projectile travel + 3.34s
Wall of Replica	Flying	800/800	39 units along the wall	Spell duration (15/30/45s)
Black Hole	Ground	800/800	Black Hole	Spell duration (4s) + 1s
Chain Frost	Flying	1000/750	Projectile	Projectile travel
Shadow Poison	Flying	300/300	Projectile	Projectile travel (1.5s) + 3.34s
Sticky Napalm	Fog modifier	500	Center of the target area	2s
Flamebreak	Flying	800/800	Projectile	Projectile travel + 3.34s
Weave	Flying	800/800	Center of the target area	8.34s
Sun Strike	Fog modifier	400	Center of the target area	4s, starting when the damage is dealt
Tornado	Flying	1200/1200	Projectile	Projectile travel + 1.75s
Deafening Blast	Flying	1200/800	Projectile	Projectile travel + 1.75s
Chaos Meteor	Flying	500/500	Meteor on the ground	While the meteor rolls + 3s
Ice Vortex	Ground	200/200	Vortex	Spell duration (12s)
Ice Blast (1)	Flying	500/500	First projectile	First projectile travel
Ice Blast (2)	Flying	500/500	Second projectile	Second projectile travel + 3.34s
Ice Blast (3)	Fog modifier	500	Center of the final area	Second projectile travel
Arctic Blast (Shiva's Guard)	Flying	800/800	Caster's position	Spell duration (1.98s) + 3.34s
Mirror Image (Manta Style)	Fog modifier	1000	Caster's position	Around 0.23s (0.1s + illusion projectile travel)
Teleport (Scroll of Teleportation)	Fog modifier	200	Destination	During the channeling time

As you may know, the area around Roshan cannot be seen until you are inside it, except for flying units (like a Scout Hawk, or the unit over Night Stalker with an Aghanim's Scepter)

This is because this area is surrounded by things called "Line of Sight Blockers", whose purpose are exactly as their name suggest.
These blockers do not prevent you from entering the area, but you cannot see through them, meaning vision is blocked from the outside of the area, as well as from the inside.

Additionally, a trigger is in place to prevent you from placing wards inside the area.

[Pingus!]

Nice, "short", concise guide, full of little nuggets of information :3
Nice work Shinjo.

E: I think you should order the heroes from highest to lowest night vision.

[antiweltteilchen]

/me iterates over LordShinjo's item slots and adds a Refrencher Orb in the slot.

awesome work as usual shinjo :>

[Pingus!]

Originally Posted by antiweltteilchen

/me iterates over LordShinjo's item slots and adds a Refrencher Orb in the slot.

awesome work as usual shinjo :>

Refrencher, I loled. Does it make you twice the french?

[SoletLuna]

/me germinates Double Shinjo D:

[Black Isle]

Compact wall of text! D:

I heard this Storm, Earth and Fire and Mirror Image gives some sight and stuff. Maybe test and add them o.o

Since I'm so good with Meat Hook, I observed that in case of a successful hook against an enemy unit it creates a dummy unit with 500 sight or something. Maybe it's my imagination.

Maybe add Lunar Blessing, doesn't really suit any particular section though. I guess you just discluded it.

[Dagguh]

The fog of war is updated every 0.4s since the start of the map.

It's a Gameplay Constant, right?

BTW. What are the Sunstrike values?

[LulzYeah Cdeqz]

Fail Pacman. He (it?) got a cut at the end of his mouth (inner)

[Lordshinjo]

Originally Posted by Phthalocyanine

Compact wall of text! D:

I heard this Storm, Earth and Fire and Mirror Image gives some sight and stuff. Maybe test and add them o.o

Since I'm so good with Meat Hook, I observed that in case of a successful hook against an enemy unit it creates a dummy unit with 500 sight or something. Maybe it's my imagination.

Maybe add Lunar Blessing, doesn't really suit any particular section though. I guess you just discluded it.

Originally Posted by Dagguh

It's a Gameplay Constant, right?

BTW. What are the Sunstrike values?

Added these. (I remember testing that Mirror Image thing, and Invoker has too many spells D: )

About the fog update time, it seems like a gameplay constant is supposed to do that, but it's actually always 0.4s.

[wd.Ripper]

Really great guide, but to be honest I do not like the tabs too much. Ofcourse it makes it nice and compact but it doesn't make it any more clear or pretty. I prefer the guides where you have to scroll all the ffing time .

Great job though.

Edit; So if Sniper ulties an enemy Balanar with Aghanims Scepter, Sniper will get full, unobstructed nightvision too?

[PEW_PEW]

Originally Posted by thisispatrick

Edit; So if Sniper ulties an enemy Balanar with Aghanims Scepter, Sniper will get full, unobstructed nightvision too?

No. The bonus vision is granted by a dummy unit, and since only the target of snipers ult has its vision shared, the sniper player would just see things the way balanar would without aghanims.

[Sinisterz]

what about the bug when u buy back and still have 500/500 range until u die again?

[Lordshinjo]

Originally Posted by Sinisterz

what about the bug when u buy back and still have 500/500 range until u die again?

This is related to the Dying Units section : buying back when you're still dying makes you be considered as always dying (even when still alive), and your vision is capped at 500/500.
Only dying again can fix it.

[Kikut]

Great job, everything about sight and whatnot in one thread.
Really appreciate it.

[Aravis]

The fog of war is updated every 0.4s since the start of the map.

This means that every 0.4s, the position of every unit, their sight range, and any sight that should be blocked or not are computed.
Then everything is displayed corresponding to this calculation.

You can then see a visual delay when the fog goes away or comes back on some cells, but this is only visual : as soon as the fog of war begins to appear or disappear, the vision has already been completely lost or gained on a particular zone.

I heared that if akasha blinks and casts her aoe in the 0.4sec update time (if she blinked at n*0.4 sec after map start) its not yet updated, and nobody will be hit.
Same thing with shaker.

Correct me if im wrong pls.

[antiweltteilchen]

you misunderstood.
the content of this sentence is that if you blink into fow it looks like your vision will expand smoothly. but actually the full vision is granted at the time the fow is updated again (meaning at max 0.4 secs later)

[MauranKilom]

and during that max of 0.4 seconds, casting scream of pain (which is based on fan of knives, which in return doesn't hit units you don't see) will have no effect (if you blinked somewhere you had no vision of)

[ElementUser]

YES a list of vision spells! ^.^

You forgot Kunkka's Torrent - it gives 4 seconds of 400/400 vision.

[Der_kleine_Tomy]

Originally Posted by MauranKilom

and during that max of 0.4 seconds, casting scream of pain (which is based on fan of knives, which in return doesn't hit units you don't see) will have no effect (if you blinked somewhere you had no vision of)

Scream of Pain is completely triggered, so it doesn't matter if it's based on fan of knives or not.

[MauranKilom]

Uh, sorry.