Collision

Collision boxes tell OpenBOR (or any other game engine) what portions of an entity are able to hit or get hit and what areas of a level are walls or platforms. In OpenBOR these boxes are geometric cubes the engine continuously compares to each other – whenever two or more cubes overlap, that’s a collision and the engine will react accordingly.

Depending on the type of collision box, it will have other properties that tell the engine how to handle the collision event. This article focuses on Attack (hitting with attacks) and Body (Receiving attacks and taking up space). Walls and platforms work on a similar principal and are covered in level design.

Multiple Boxes

OpenBOR supports multiple collision boxes per frame. To define a second box of any type, add collision.index {index} with your desired index and then define a set of properties for the next box. You may use any integer value for {index}. All subsequent collision box properties below collision.index {index} now act on the new index.

You can repeat this process to add a third box, a forth box, and so on. To adjust or disable the boxes, again use collision.index {index} to define which box you wish to act on, then disable or adjust the box properties as you would a single occurrence.

When two or more attack boxes overlap a body box or body boxes, OpenBOR will acknowledge a single collision with the earliest attack and body boxes in defined order taking priority.

Tip: There’s no hard code limit, but don’t get carried away with this feature. Even high precision vs. fighters like Street Fighter and King of Fighters typically use just two or three body boxes and one attack box. Most beat em’ up games never need more than one of each except for special cases (ex. oddly shaped limbs).

Attack

Attacks hit and presumably cause damage to other entities. To define an attack, add the necessary attack commands from list below immediately before the frame. In most cases you only need the basic dimensions and damage value. The other attack properties are optional and most are disabled by default.

Once defined, an attack remains active throughout remainder of the animation unless you redefine it. To disable an attack, add attack 0 or attack none before a frame.

Command List

Example

Single

This example defines a single attack box that knocks down and does 10 points of damage, then closes the box on the subsequent frame. Notice only the necessary properties are defined. Order is irrelevant.

attack.position.x 58
attack.position.y 90
attack.size.x 92
attack.size.y 25
attack.reaction.fall.force 1
attack.reaction.pause.time 10
attack.damage.force 15
attack.effect.hit.flash.model flash_fatal_fury

frame data/chars/terry/atk_j_side_kick_c_1.png

attack none

frame data/chars/terry/atk_j_side_kick_c_1.png

Multiple

This example takes advantage of multiple boxes to place a more accurate attack area around Ryu’s leg. The second box has an index of 1. Since we didn’t bother to define an index for the first box, it gets a default index of 0. Unless the target is really close, we want the contact area (and thus flash spawns) to be around Ryu’s foot, so we place that box first in order to give it priority. The attack definitions are otherwise identical to single boxes. On the following frame, we close both the attack boxes.

attack.damage.force 12
attack.effect.hit.flash.model flash_fatal_fury
attack.reaction.fall.force 1
attack.reaction.pause.time 12
attack.position.x 138
attack.position.y 44
attack.size.x 32
attack.size.y 26
	
collision.index 1

attack.damage.force 12
attack.effect.hit.flash.model flash_fatal_fury
attack.reaction.fall.force 1
attack.reaction.pause.time 12
attack.position.x 112
attack.position.y 61
attack.size.x 33
attack.size.y 25

frame	data/chars/ryu/20_3.png

collision.index 0
attack none

collision.index 1
attack none

frame   data/chars/ryu/20_4.png

Body

Body boxes detect incoming attacks. If an entity doesn’t have a body box on a given frame, it can’t detect attacks and is effectively invincible from conventional hits. Defining a body box is nearly identical to attack boxes, except body boxes are far simpler as they have fewer properties.

To end a body box, add bbox 0 or bbox none before a frame.

Example

Single

This example defines a single body box to detect hits.

bbox.position.x	66
bbox.position.y 49
bbox.size.x	38
bbox.size.y	98

Multiple

This example takes advantage of multiple boxes to place a more accurate hit area area area around Ryu. The second box has an index of 1, and the third an index of 2. Since we didn’t bother to define an index for the first box, it gets a default index of 0. Unless the target is really close, we want the contact area (and thus flash spawns) to be around Ryu’s head, then body, so we place the boxes in order from head to feet to give higher areas priority. The body definitions are otherwise identical to single boxes.

bbox.position.x	78
bbox.position.y 48
bbox.size.x	25
bbox.size.y	21

collision.index 1

bbox.position.x	67
bbox.position.y 57
bbox.size.x	35 
bbox.size.y	51

collision.index 2

bbox.position.x	62
bbox.position.y 103
bbox.size.x	47 
bbox.size.y	46

frame	data/chars/ryu/idle_0.png

collision.index 0
bbox none

collision.index 1
bbox none

frame	data/chars/ryu/idle_1.png

Advanced

Hit Placement

Each time a collision occurs, OpenBOR records the location and several other data points into a structure called lasthit. This is then used for items like the native flash effects. Lasthit is available as a system variable and as local vars in didhit and takedamage scripts.

Hit location is the calculated center point where the respective collision boxes overlap on each Axis.

Legacy Attack

Legacy attack boxes use a single attack command with multiple parameters. Additional parameters are available through separate commands we call “Supplements”.

Note: Legacy attack commands are depreciated and will not receive further updates.It is highly recommended any new projects utilize the current attack box commands.

Base commands

Attack

Default legacy attack box. Other than {#}, you cannot omit an optional parameter and use any other parameters rightward. For example, if you want to include a {pausetime} value, you must also include {power}, {block}, and {noflash}.

attack{#} {x} {y} {right} {down} {damage} {power} {block} {noflash} {pausetime} {z}

• {#} – See attack.damage.type (numbers only). {#} is part of the command name, no spaces. As an example, if you wanted an attack type 2, you would write attack2 {x} {y} .... Optional. If omitted, defaults to 1.
• {x} – See attack.position.x.
• {y} – See attack.position.y.
• {right} – See attack.size.x.
• {down} – See attack.size.y.
• {damage} – See attack.damage.force.
• {power} – Optional. See attack.reaction.fall.force.
• {block} – Optional. See attack.block.penetrate.
• {noflash} – Optional. See attack.effect.hit.flash.disable.
• {pausetime} – Optional. See attack.reaction.pause.time.
• {z} – Optional. See attack.size.z.1 and attack.size.z.2. Legacy Z affects both directions.

Blast

Same as Attack other than following:

blast {x} {y} {right} {down} {damage} {block} {noflash} {pausetime} {z} 

• attack.damage.type = Blast. Note blast type does nothing on its own and defaults to type 1 reactions.
• attack.reaction.fall.force = 1.
• attack.reaction.fall.velocity.x = is 2.083.
• attack.damage.mode = 1.

Burn

Same as Attack other than the following:

Burn {x} {y} {right} {down} {damage} {knockdown} {block} {noflash} {pausetime} {z}

• attack.damage.type = Burn.

shock

Same as attack# other than the following:

shock {x} {y} {right} {down} {damage} {knockdown} {block} {noflash} {pausettime} {z} 

• attack.damage.type = Shock.

Freeze

Same as Attack other than the following:

freeze {x} {y} {right} {down} {damage} {time} {block} {noflash} {pausetime} {z} 

• attack.damage.type = Freeze. Note freeze type does nothing on its own and defaults to type 1 reactions.
• attack.reaction.freeze.mode = 1.
• {time} – See attack.reaction.freeze.time.
• attack.map.index = 1.

Steal

Same as Attack other than the following:

steal {x} {y} {right} {down} {damage} {knockdown} {block} {noflash} {pausetime} {z}

• attack.damage.type = Steal. Note steal type does nothing on its own and defaults to type 1 reactions.
• attack.damage.steal = 1.

Supplements

grabin

grabin {type} {distance}

• {type} – See attack.reposition.mode.
• {distance} – See attack.reposition.distance.

Fastattack 1

When enabled, applies a static value of attack.reaction.invincible.time 10.

Forcedirection

forcedirection {dir}

• {dir} – See attack.reposition.direction.

Damageonlanding

damageonlanding {value} {type} 

• {value} – See attack.damage.land.force.
• {type} – See attack.damage.land.mode.

Dropv

dropv {height} {speedx} {speedz}

• {height} – See attack.reaction.fall.velocity.y.
• {speedx} – See attack.reaction.fall.velocity.x.
• {speedz} – See attack.reaction.fall.velocity.z.

Nokill

nokill {bool}

• {bool} – See attack.damage.lethal.disable.

stun {int}

• {int} – See attack.reaction.freeze.mode.

Seal

seal {time} {energy} 

• {time} – See attack.seal.time.
• {energy} – See attack.seal.cost.

Forcemap

forcemap {map} {time} 

• {map} – See attack.map.index.
• {time} – See attack.map.time.

Noreflect

noreflect {bi} 

{bi} – See attack.reaction.pain.disable.

Jugglecost

jugglecost {int} 

• This command limits juggling ability of the attackbox.
• Juggling means attacking falling opponents (assuming they are vulnerable while falling). It doesn’t matter if the attackbox knocks down or not cause juggling always knock down opponent.
• This command is used in conjunction with ‘jugglepoints’ (see Header Data above).
• The command works like this:
  • If attackbox hits opponent whose ‘jugglepoints’ is higher than or equal with ‘jugglecost’, the attack will connect. At this condition, opponent’s ‘jugglepoints’ will be subtracted by that ‘jugglecost’. This drops ‘jugglepoints’ which limits juggling ability. If attackbox hits opponent whose ‘jugglepoints’ is lower than ‘jugglecost’, the attack will not connect. At this condition, opponent’s ‘jugglepoints’ will remain the same.

OTG

OTG {bi}

{bi} – See attack.ground.mode.

Guardcost

guardcost {int} 

{int} – See attack.block.cost.

• Defines how much ‘guardpoints’ will be subtracted from opponent if they block this attack.

DOT

DOT {Index} {Time} {Mode} {Force} {Rate} 

• {index} – See attack.damage.recursive.index.
• {time} – See attack.damage.recursive.time.
• {mode} – See attack.damage.recursive.mode.
• {force} – See attack.damage.recursive.force.
• {rate} – See attack.damage.recursive.rate.

Staydown

staydown {rise} {riseattack} 

{rise} – See attack.staydown.rise.time.

{riseattack} – See attack.staydown.attack.time.

Legacy Body

Legacy body box commands are nearly identical to legacy attack box commands in format.

Note: As with legacy attack commands,legacy body commands are depreciated and will not receive further updates.It is highly recommended any new projects utilize the current body box commands.

body {x} {y} {width} {height} {depth back} {depth front}

• {x} – See body.position.x.
• {y} – See body.position.y.
• {width} – See body.size.x.
• {height} – See body.size.y.
• {depth back} – See body.size.depth.back.
• {depth front} – See body.size.depth.front. If omitted, {depth back} sets depth in both directions.

bboxz {depth back} {depth front} – See body.size.depth.back and body.size.depth.front