Collision size

Collision size ( $col$ ) is a unit's internal size that cannot be passed through by other units. This allows units to block each other with their bodies. Most heroes have the same collision size, regardless of their graphical model. Phased status allows units to ignore collision size.

Mechanics

The collision sizes of units is not directly set by a number in their data. Instead, collision sizes are standardized for all units, with the use of bounds hull names.

The following hull sizes exist, corresponding to the following collision sizes (from largest to smallest):

Hull Name	Size
`DOTA_HULL_SIZE_BUILDING`	298
`DOTA_HULL_SIZE_TOWER`	144
`DOTA_HULL_SIZE_FILLER`	96
`DOTA_HULL_SIZE_HUGE`	80
`DOTA_HULL_SIZE_HERO`	24
`DOTA_HULL_SIZE_REGULAR` `DOTA_HULL_SIZE_SIEGE`	16
`DOTA_HULL_SIZE_SMALL`	8
`DOTA_HULL_SIZE_SMALLEST`	2

Collision Size Comparison

Heroes

Heroes	Collision size
	18
	27

Units

Units	Collision size
Fiend's Gate	112
Astral Spirit, Beetle, Courier, Earth, Eidolon, Fire, Healing Ward, Jex, Lycan Lane Wolf, Lycan Wolf, Mega Ranged Creep, Minor Imp, Necronomicon Archer, Nether Ward, Nimbus, Observer Ward, Phantom, Proximity Mine, Psionic Trap, Ranged Creep, Roshan's Banner, Sentry Ward, Skeleton Archer, Skeleton Warrior, Spiderite, Spiderling, Spin Web, Storm, Super Ranged Creep, Void	18
Alpha Wolf, Ancient Black Dragon, Ancient Black Drake, Ancient Frostbitten Golem, Ancient Granite Golem, Ancient Ice Shaman, Ancient Rock Golem, Ancient Rumblehide, Ancient Thunderhide, Boar, Centaur Conqueror, Centaur Courser, Dark Troll Summoner, Fell Spirit, Ghost, Giant Wolf, Harpy Scout, Harpy Stormcrafter, Hawk, Hellbear, Hellbear Smasher, Hill Troll, Hill Troll Berserker, Hill Troll Priest, Homing Missile, Ignis Fatuus, Kobold, Kobold Foreman, Kobold Soldier, Mars Soldier, Mud Golem, Ogre Bruiser, Ogre Frostmage, Phoenix Sun, Plague Ward, Roshan, Satyr Banisher, Satyr Mindstealer, Satyr Tormenter, Shard Golem, Spirit Bear, Sticky Bomb, Tempest Double, Tormentor, Vhoul Assassin, Warlock Golem, Warpine Raider, Wildwing, Wildwing Ripper	27
Anchor, Death Ward, Familiar, Flagbearer Creep, Forged Spirit, Ice Spire, Lookout, Mega Flagbearer Creep, Mega Melee Creep, Melee Creep, Necronomicon Warrior, Serpent Ward, Super Flagbearer Creep, Super Melee Creep, Tombstone, Tornado, Treant	36
Undying Zombie, Wraith King Skeleton	4
Mega Siege Creep, Siege Creep, Super Siege Creep	40
Power Cog	80

Buildings

Buildings	Collision size
Effigy Building, Lotus Pool, Outpost, Twin Gate	112
Fountain, Tower (Tier 1), Tower (Tier 2), Tower (Tier 3), Tower (Tier 4)	144
Melee Barracks, Ranged Barracks	160
Watcher	18
Ancient	314.73/389.96

Area of Effect

Ability area target indicator — Indicator of area target spells

Collision size affects the size of an area of effect, if an ability is cast as a ground-targeted ability, the affected target's collision size is also considered as a buffer range for ability, and therefore increasing the ability's maximum area of effect range.

However, if an ability is cast centered on the caster (with ↓↓ Double-tapping), the caster's collision size is ignored and no buffer range is added.

The maximum area of effect for area-targeted abilities is defined as:

max\{aoe\} = {aoe}_b + {col}_t

With aoe_b being the base effect radius and col_t the target's collision size.

Example 1: What is the maximum area of effect range if Dark Seer casts Surge with level 25 on Abaddon?

Range values:

Level 25 Surge talent radius: 350

Collision size values:

Abaddon: 27

max\{c\} = 350 + 27 = 377

Surge in this example has a maximum area of effect range of 377 in this example.

Example 2: Invoker with Aghanim's Scepter used Cataclysm. What's the maximum area range for enemy Meepo and Abaddon?

Abilities

Abilities Based on Collision Size

Earthshaker - Fissure

Fissure Pathing Block Radius: 24
The segments have a collision size of 24, and a distance of 8.25 between each other, with the first one being placed 8.25 range in front of Earthshaker.
This means the actual length of the Fissure can only be a factor of 56.25.
The length factor is defined as $\text{sides} \times col + d$

Ignoring Collision Size

Phased is a status that allows units to pass through other units, ignoring collision size. Phased units can freely walk through any other unit, including wards, but excluding buildings and trees. Other units can also walk through a stationary phased unit as if it is not there.

There are two different kinds of phased movement, pathing through units, and the rare kind which allows the unit to walk through anything, including buildings, cliffs and trees, which is more commonly referred to as unobstructed movement.

Flying movement is similar to phased movement, with only very small differences, one being that flying units hover a certain distance above the ground.

Abilities Providing Phased Movement

These abilities provide phased movement which allows moving through units:

¹ Shadow Fiend becomes phased during the cast time of Requiem of Souls.

Abilities Providing Unobstructed Movement

Free pathing (also known as unobstructed movement or flying movement) allow affected units to path through buildings, cliffs and trees, on top of allowing them to path through other units. There is no limit to their movement and nothing will block them, all sources of flying give units unobstructed movement. Uphill miss chance does not apply to flying units.

The following abilities provide unobstructed movement:

Batrider – Firefly
Broodmother – Spin Web
Centaur Warrunner – Stampede¹
Dragon Knight – Elder Dragon Form¹
Giant's Ring – Giant's Foot
Lich – Sinister Gaze
Legion Commander – Duel
Nyx Assassin – Vendetta
Nyx Assassin – Burrow¹
Spectre – Spectral Dagger
Spectre – Dispersion^{2 4}
Spectre – Haunt⁴
Spectre – Shadow Step^{1 4}
Lua error: Found no Cargo data for "Spider Legs - Scurry".
Terrorblade – Reflection⁴
Visage – Silent as the Grave¹
Wraith King – Wraith Delay¹

¹ Requires

Aghanim's Scepter.

² Requires

Aghanim's Shard.

³ Requires

talent.

⁴ Illusions created by these abilities have unobstructed pathing.

Tree-walking

The following abilities grants tree-walking, a buff that allows unobstructed movement through trees.

Tree-walking Granting Abilities

Hoodwink - Scurry

Passive Tree Search Radius: 275
Grants phased movement and tree-walking to Hoodwink within the tree search radius.
Treant Protector - Nature's Guise

Innate ability, does not need to be learned.

Permanently Phased

The following units are permanently phased:

Permanently Phased Units

Spin Web – Phased
Lua error: Found no Cargo data for "Courier - Level Bonuses".
Beetle – Phased
Fire – Phased
Observer Ward – Phased
Sentry Ward – Phased
Healing Ward – Phased
Ignis Fatuus – Phased
Phoenix Sun – Phased
Proximity Mines – Phased
Lua error: Found no Cargo data for "Techies - Stasis Trap".
Lua error: Found no Cargo data for "Techies - Remote Mines".
Roshan – Strength of the Immortal
Psionic Trap – Phased

Flying Movement

Abilities that turn the caster into a flying unit

Trees

Main Article: Trees

Trees are a prominent terrain feature in Dota 2. They make up a large amount of the map and are very prominent in the forests that separate the lanes and border the map. Trees block vision and are normally impassable.

Despite the varying appearance and apparent size of the various trees, all permanent trees have an block size of a 128x128 unit square.

Planted Trees

Planted trees have a smaller collision size and block less vision than regular trees.

Planted Tree Sources

Hoodwink - Acorn Shot

Creates a tree when targeting the ground.
Hoodwink - Decoy

Send a decoy illusion to the target location. When the illusion is attacked or hit by a unit-targeted ability, it is destroyed and plants a tree in its place that applies a lesser Bushwhack to enemy heroes around it.
Iron Branch - Plant Tree

Consumes the item upon cast and plants a tree, with a smaller collision size.
Tango doubles the health regeneration bonus duration when cast on an Ironwood Tree.
Nature's Prophet - Sprout

Creates a ring of trees around the targeted point or unit.