Add ZIndex, YSort, and SortBias 2d components
#19463
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tychedelia
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IceSentry and
NthTensor
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| /// A marker component that enables Y-sorting (depth sorting) for sprites and meshes. | ||
| /// | ||
| /// When attached to an entity, this component indicates that the entity should be rendered | ||
| /// in draw order based on its Y position. Entities with lower Y values (higher on screen) | ||
| /// are drawn first, creating a depth illusion where objects lower on the screen appear | ||
| /// in front of objects higher on the screen. | ||
| #[derive(Component, Default, Debug, Clone)] | ||
| pub struct YSort; |
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Setting YSort per-sprite seems like it might be confusing to me. Will we be able to resolve situations where you have multiple overlapping sprites, some with YSort, some without, in a consistant way?
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Right now, for entities on the same z index layer, an entity with y sort enabled will always sort before one without it. Not sure if this is intuitive but it is consistent.
| z_index: 0, | ||
| y_sort: false, | ||
| sort_bias: None, |
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Text2d needs to support z index too.
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As long as they both just wrap an i32 and higher values are on top, I think it would be okay to use the same ZIndex component for both UI and 2d. bevy_ui already depends on bevy_sprite for the texture slicing API. We'd just need to be careful to make sure all the documentation points out clearly how it behaves in each context.
We just merged #17575 which could help. I'm the wrong person to ask about 2d design patterns, but it's not clear to me that children should always be drawn above their ancestors, although I realize this is a pattern that using z position plus transform propagation makes trivial and we are breaking. Would appreciate input here from others. |
I don't think we can assume this. We need to make it possible for children to be drawn in front of behind their ancestors, depending on artist intent. |
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I don't think we can assume it, but I do think it's a good default :) |
I guess the question is, what does this look like? Do we have a |
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It feels to me like y-sorting is more a property of an individual layer rather than individual sprites. Wouldn't you want all sprites in the same layer to be y sorted? Does the y sort take into account the anchor point at all? |
Probably? But again I think this is more a function of questions around patterns for inheritance/propagation. At the end of the day, they will be sorted one by one and so I think it still makes sense for the components to apply to individual entities if you want. I wouldn't want to take away this fine grained control just add other tools for making common use cases easier. |
bevy_lunex does this. by default every child is one z step above its parent. and there's an override component (with i wonder if different variants like that can be useful here |
Objective
Using Z transform for sprites and 2d meshes is gross! Users expect familiar sorting strategies.
Solution
Adds 3 new sorting components for 2d:
ZIndex: sorts entities into layers and always takes priority.YSort: sorts entities in eachZIndexlayer by their Y transform.SortBias: an arbitrary bias that is either added to Y transform or used as a secondary sort value.TODO:
ZIndex.Testing
Tested a bunch of examples, might be more broken.