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Loaded entity position ignores pivot #290

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Koopa1018 opened this issue Jan 12, 2024 · 4 comments · May be fixed by #294
Open

Loaded entity position ignores pivot #290

Koopa1018 opened this issue Jan 12, 2024 · 4 comments · May be fixed by #294

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@Koopa1018
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In my LDtk project, I have defined a number of entities with a bottom pivot point:
image

Based on my work in other apps, I expect the pivot to change how entities are placed relative to the position shown--and indeed, in LDtk I see this exact thing happening.
image
Left: origin on the bottom. Right: origin in center, moved to fill the same space. Note the changed Y coordinate.

But when those entities are loaded into Bevy:
image
What the pfargtl?! The Transform component stores the object's center instead of its origin!

I've compensated in my code. But it's a huge bother to have to do complicated math instead of just reading a component which, frankly, ought to match LDtk's behavior in the first place (apart from Y-down coordinates).
@Koopa1018 Koopa1018 changed the title Loaded entity translation does not respect origin Loaded entity position ignores pivot Jan 12, 2024
@Trouv
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Trouv commented Jan 13, 2024 •
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Yep, I agree this is bad behavior. It's a holdover from when this plugin was originally written, which was before the Anchor in bevy sprites existed. Sprites were just anchored to their center, and so to make spawned entities w/ sprites have the same visual location in LDtk, the transform was adjusted instead. Now, it's well past time we switch to using the Anchor to pivot entities instead of the transform.

Koopa1018 added a commit to Koopa1018/bevy_ecs_ldtk that referenced this issue Jan 16, 2024
@Koopa1018
Use un-pivoted conversion for entity translation
d9bc287 
This is the basic ingredient needed to fix Trouv#290. There's a lot of things which will potentially break if this is done in isolation, so there's a lot more work ahead.
@Koopa1018 Koopa1018 linked a pull request Jan 16, 2024 that will close this issue
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@Koopa1018
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Ahh, historical workarounds....that makes sense 🙂

@DavidHospital
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Any update on this issue? Is there a workaround while #294 is still open?

@Koopa1018
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I know I had one. Lemme see if I can find it....
Ah, here it is. Straight from my janky codebase.

use bevy::{prelude::*, math::{vec2, ivec2}};
use bevy_ecs_ldtk::EntityInstance;

pub fn position_pivoted(position: Vec2, entity: &EntityInstance) -> Vec2{
	// For some reason, the GlobalTransform position is the
	// CENTER POINT of the entity, not the point defined in LDtk.
	// Compensate for that by applying origin to the entity.
	
	// offset relative to pivot
	position + (
		// start with 0-1 pivot
		entity.pivot
		// adjusted so center is actually centered
		- vec2(0.5, 0.5)
	)
	// Scale it to object size
	* ivec2(entity.width, entity.height).as_vec2()
	// invert from Y-down to Y-up
	* vec2(1.0, -1.0)
}

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Fix ignored entity pivot Koopa1018/bevy_ecs_ldtk
3 participants
@Trouv @DavidHospital @Koopa1018