Player System

Source: client/engine/systems/SystemsFunctions/PlayerSystem.cpp

Purpose: Update player animation based on vertical velocity and sync rotation of the player and its children based on horizontal velocity.

Components used:

• PlayerTag (contains speed_max and other player properties)
• Velocity (reads vx and vy)
• AnimatedSprite (updates current_frame)
• Transform (updates rotationDegrees for player and children)

Behavior

Vertical animation

animated_sprite.current_frame is set according to vertical velocity (velocity.vy):

Condition	Frame	Animation
vy > 200.f	0	Fast downward
vy >= 75	1	Moderate downward
vy < -200.f	4	Fast upward
vy <= -75	3	Moderate upward
Else	2	Neutral

Horizontal rotation

The system computes a rotation angle based on horizontal velocity:

float rotation = velocity.vx / player_tag.speed_max * 5.f;
transform.rotationDegrees = rotation;

This gives a tilt proportional to horizontal speed.

Child sync

Rotation propagates to all child entities:

for (auto &&[j, child_transform] : make_indexed_zipper(transforms)) {
    if (child_transform.parent_entity.has_value() &&
        child_transform.parent_entity.value() == i) {
        child_transform.rotationDegrees = rotation;
    }
}

Child assets (e.g., the charge effect) follow the same tilt.

Main signature

void PlayerSystem(Eng::registry &reg,
    Eng::sparse_array<Com::PlayerTag> const &player_tags,
    Eng::sparse_array<Com::Velocity> const &velocities,
    Eng::sparse_array<Com::Transform> &transforms,
    Eng::sparse_array<Com::AnimatedSprite> &animated_sprites);

Notes

• Animation thresholds (200.f, 75) are hard-coded in current logic.
• The rotation factor (5.f) sets the max tilt amplitude.
• This system does not apply physics; it only syncs visuals to velocity.
• Child lookup scans all transforms; could be optimized with Transform.children (like ChargingShowAssetPlayerSystem).

Possible improvements

1. Optimization: Use transform.children instead of scanning all transforms for children.
2. Configuration: Externalize animation thresholds and rotation factor into constants or PlayerTag.
3. Interpolation: Smoothly transition between animation frames.
4. Vertical rotation: Add slight pitch based on vy for more dynamism.