Open
Description
Enhancement request:
Refactor hitboxes, adjusted hitboxes, and optimize their usage within spatial hashes.
What should be added/changed?
Broad goals
- Avoid recomputing adjusted hitbox in broad-phase collision check
- avoid
left/right/top/bottom; use newhit_box.radiusinstead
- avoid
- Make
HitBoxits own class - Flyweight pattern to share single
HitBoxacross manySpriteandTextureinstances - Defer spatial hash updates until collision detection; do not eagerly update hashes when a sprite is moved
Further explanation
Why defer spatial hash updates?
Naive code will often do something like this:
sprite.center_x = new_x
sprite.center_y = new_y
if near_gravity_well:
sprite.center_y -= 2
sprite.radians += angularToday, this code triggers spatial hash removal and re-add 3-4 times per frame. We should avoid that. The first modification marks the spatial hash entry as "dirty." Then collision detection will fix the hash on-demand.
Class Diagram
This is not rigorous UML
classDiagram
Sprite -- SpatialHashEntry
SpatialHashEntry -- SpatialHash
Sprite -- SpatialHash
Sprite -- HitBox
Sprite -- AdjustedHitBox
Texture -- HitBox
class Texture {
hit_box: HitBox
---
}
note for Texture "Gets an auto-computed HitBox automatically, as a convenience.\nOther code may or may not choose to use it.\nSprites can borrow this hit_box or have their own."
class Sprite {
hit_box: HitBox
adjusted_hit_box: AdjustedHitBox
spatial_hash_entries: list[SpatialHashEntry]
}
class HitBox {
points: list[Point]
radius: int -- max radius for broad-phase collision checks
---
flyweight, should be immutable and shared w/Texture. Do *not* put adjusted_hit_box here!
}
class SpatialHashEntry {
dirty: bool
spatial_hash: SpatialHash
min_point: hashed Point
max_point: hashed Point
}
class SpatialHash {
dirty: bool
}
class AdjustedHitBox {
TBD is this merely a list of points like today?
}
note for Sprite "Any movement of sprite sets `dirty` to true\non all the sprite's `SpatialHashEntry`s and `SpatialHash`s"
note for Sprite "Consider renaming to Collidable to decompose monolithic Sprite"
note for SpatialHash "Any collision detection routines first check `dirty`\nand update hash positions for all `dirty` entries on-demand."