Lines are always behind sprites in a 2d scene

[thisjaiden]

Given a 2d orthographic camera and some SpriteBundles, debug lines will never appear in front of the sprites no matter what Z value is used for either. I'm not sure if this is intentional but it also happens when with_depth_test is enabled.

bevy v0.7.0
bevy_debug_lines v0.7.1
rustc v1.59.0

[Toqozz]

Hmmm... I wonder if we should be setting the fragment depth in the 2d shader like we do in the 3d one. Will check on this when I get the time.

[thisjaiden]

It looks like bevyengine/bevy#4011 was fixed in bevy v0.7.0, so it may be possible to join the 2d and 3d shaders at the same time. I'll look into this, but I don't have much experience with shaders.

[Indeximal]

I've run into the same issue. Would super appreciate it if this got fixed.

[Toqozz]

I'm running the following example:

use bevy::prelude::*;

use bevy_prototype_debug_lines::{DebugLines, DebugLinesPlugin};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugin(DebugLinesPlugin::default())
        .add_startup_system(setup)
        .add_system(demo)
        .run();
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    let mut camera = OrthographicCameraBundle::new_2d();
    camera.transform = Transform::from_translation(Vec3::new(0.0, 0.0, 5.0));

    commands.spawn_bundle(camera);
    commands.spawn_bundle(SpriteBundle {
        texture: asset_server.load("icon.png"),
        ..default()
    });
}

fn demo(mut lines: ResMut<DebugLines>) {
    lines.line_colored(
        Vec3::new(-400.0, 0.0, -1.0),
        Vec3::new(400.0, 0.0, -1.0),
        0.9,
        Color::GREEN,
    );
}

And the line draws on top of the sprite -- am I missing something?

I'll think about making with_depth_test do something for 2d, but as a workaround you can just make the z position -999 or something like that.
EDIT: actually, it looks like -1 z just draws on top, but -2 etc doesn't. Dunno what's happening there.

[Toqozz]

Ok I pushed a change to master that should make lines always draw on top of sprites, if my understanding is correct.

Let me know if it doesn't work properly.

Will push a new version out shortly if there are no issues.

[thisjaiden]

Okay- this is bizarre.
I was always using positive Z coordinates for my lines, which may have caused the original problems.

Using master, lines now draw on top of sprites if the line's Z coordinate is in front of the sprite's Z coordinate. Somehow "disabling" depth fixed it.

Negative Z values make the disappear. (Outside of orthographic camera's default view?)

There's a new issue that lines always draw behind Text2dBundles, but that's a separate issue and may be related to how bevy separates UI from the scene. I consider this fixed, if in a strange way.

Side note: I am not near my main workstation so I am running these tests on an entirely different platform. I doubt there's any platform semantics but I will check tomorrow.

Thank you for the quick fix!

[Indeximal]

Sadly I don't see the same result for sprites not within the (0, 1) z-interval. Running this example, where the line is still occluded by the sprite:

use bevy::prelude::*;
use bevy_prototype_debug_lines::{DebugLines, DebugLinesPlugin};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugin(DebugLinesPlugin::default())
        .add_startup_system(setup)
        .add_system(demo)
        .run();
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    let camera = OrthographicCameraBundle::new_2d();
    commands.spawn_bundle(camera);

    commands
        .spawn_bundle(SpriteBundle {
            texture: asset_server.load("icon.png"),
            transform: Transform::from_translation(Vec3::new(0.0, 0.0, 100.0)),
            ..default()
        })
        .insert(Name::new("Sprite"));
}

fn demo(mut lines: ResMut<DebugLines>) {
    lines.line_colored(
        Vec3::new(-400.0, 0.0, 999.0),
        Vec3::new(400.0, 0.0, 999.0),
        0.9,
        Color::GREEN,
    );
}

From the testing I've done it seems that lines are rendered "correctly" at 999, because if I change the near clip plane the line disappears. However, they are still rendered behind the sprite, if the sprite has z > 1.0. Anything from 0.0 to 1.0 works as expected.
Thanks for your quick reaction :)

EDIT: further testing indicates that in the (0, 1) z-interval (of the sprite) the lines is always drawn on top. Thus I can't replicate @thisjaiden 's observation.

[Toqozz]

So bizarre. I tried a bunch of different coordinates to see if it changed after the latest master change, but it seemed to always be on top.

I'll have to try look into this further and perhaps ask other bevy people more about the 2d pipeline.

[thisjaiden]

I'll do some more testing and provide results with examples later today.

[thisjaiden]

Upon further inspection it's probably something in my environment. I modified the example to draw various lines at different depths (see my fork) and got the expected results: all lines within clipping bounds render on top of the sprite and those outside the camera's view do not render. This issue can be closed whenever you see fit! Thank you again for the quick work.

[benedikt-jensen]

I have the same issue. I don't know why, but each time I run my code I get a different ordering. I had the same issue with bevy_prototype_lyon.

[Indeximal]

For the time being, setting all z translations to be between 0 and 1, but not changing the camera (still 999 near field and 0 far field) has worked perfectly for me.
Since z values are all floats anyway, I just devided all of them by 1000.
@lordbenedikt Different orderings might be due to equivalent z translations, so maybe check your ordering?

[benedikt-jensen]

That works for you?
@Indeximal I used your code but changed z tranlations to be between 0 and 1.

use bevy::prelude::*;
use bevy_prototype_debug_lines::{DebugLines, DebugLinesPlugin};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugin(DebugLinesPlugin::default())
        .add_startup_system(setup)
        .add_system(demo)
        .run();
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    let camera = OrthographicCameraBundle::new_2d();
    commands.spawn_bundle(camera);

    commands
        .spawn_bundle(SpriteBundle {
            texture: asset_server.load("head.png"),
            transform: Transform::from_translation(Vec3::new(0.0, 0.0, 0.3)),
            ..default()
        })
        .insert(Name::new("Sprite"));
}

fn demo(mut lines: ResMut<DebugLines>) {
    lines.line_colored(
        Vec3::new(-400.0, 0.0, 0.5),
        Vec3::new(400.0, 0.0, 0.5),
        0.9,
        Color::GREEN,
    );
}

No matter what I change the z to, now the line is always in the back. Am I doing something wrong?

[thisjaiden]

+1, experiencing ordering randomness/issues too after further inspection. Seems to order all lines either behind or in front, but I'm not sure what's deciding when they're ordered last or first in rendering.