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Add Grounded marker for KinematicCharacterController #504

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Jondolf opened this issue May 9, 2024 · 0 comments
Open

Add Grounded marker for KinematicCharacterController #504

Jondolf opened this issue May 9, 2024 · 0 comments
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A-Integration very bevy specific C-Enhancement New feature or request D-Medium P-Medium S-not-started Work has not started

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@Jondolf
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Jondolf commented May 9, 2024

A pretty common question I see people ask is "how do I know if my character is grounded?"

This is currently done by querying for the KinematicCharacterControllerOutput component and checking the is_grounded property.

fn log_grounded(controllers: Query<(Entity, &KinematicCharacterControllerOutput)>) {
    for (entity, output) in &controllers {
        println!("Entity {:?} touches the ground: {:?}", entity, output.grounded);
    }
}

However, in my opinion, a more idiomatic approach would be a Grounded marker component. Paired with the Without filter, it would make some systems more ergonomic while also reducing the amount of iteration. For example, a simple jumping system could filter out entities that aren't grounded:

fn jump(
    mut jump_event_reader: EventReader<JumpEvent>,
    mut controllers: Query<&mut Velocity, With<Grounded>>,
) {
    for event in jump_event_reader.read() {
        for (jump_impulse, mut velocity) in &mut controllers {
            // A KCC isn't controlled like this, but imagine it works for demonstration purposes.
            velocity.linvel.y = event.jump_impulse;
        }
    }
}

For the boolean value, the idiomatic approach is to use Has:

fn log_grounded(controllers: Query<(Entity, Has<Grounded>)>) {
    for (entity, is_grounded) in &controllers {
        println!("Entity {:?} touches the ground: {:?}", entity, is_grounded);
    }
}

If desired, the name could also be more specific like CharacterGrounded or even KinematicCharacterGrounded, but I think just Grounded is fine too.

@Vrixyz Vrixyz added D-Medium P-High arbitrary important item S-not-started Work has not started A-Integration very bevy specific P-Medium and removed P-High arbitrary important item labels May 21, 2024
@Vrixyz Vrixyz added the C-Enhancement New feature or request label May 28, 2024
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