TilemapChunk texture bleeding

[Badgerup1510]

Bevy version and features

bevy = "0.17.3"
perlin2d = "0.2.6"
accesskit = "0.21"

What you did

I am using the TilemapChunk Component introduced in bevy 0.17. I set up a simple 'wires' chunk. The background of the image is transparent.
It was spawned as a Child of an entity in this manner:

let chunk_size = UVec2::splat(3); 
let tile_display_size = UVec2::splat(64); 
let tile_data: Vec<Option<TileData>> = (0..chunk_size.element_product())
    .map(|i| i % 16)
    .map(|i| Some(TileData::from_tileset_index(i as u16)))
    .collect();

               // Most of spawn code omitted for simplicty
                (
                    WorldObjectLayer::Wire,
                    TilemapChunk {
                        chunk_size,
                        tile_display_size,
                        tileset: assets.load("textures/wires.png"),
                        ..default()
                    },
                    TilemapChunkTileData(tile_data.clone()),
                    Transform::from_xyz(0.0, 0.0, 4.0),
                ),

ImagePlugin is set to nearest:

app.add_plugins(DefaultPlugins.set(ImagePlugin::default_nearest()));

What went wrong

I expected a clear distribution of tiles. I found a distribution of tiles but with slight bleeding of assets along the edges. See attached image

Additional information

I would have to suspect this is either a bug with how the Tilemap's image is constructed in Bevy or it is some sort of graphics API issue with small textures.

The texture is 16 pixels wide and 256 tall.

[grind086]

I just brought up something that looks similar on discord: https://discord.com/channels/691052431525675048/1367261228459884604/1452893718725263421

Was just fiddling around and finally figured out where the rounding error I've been running into is. In the shader the local_uv isn't using a clamped value, so it gets the wrong value when in.uv is >= 1.
And even with vertex UVs only in the range [0, 1] you can still get fragments with an input uv > 1 depending on camera position, so you get flickering seams between chunks.

I have a little demo reproduction here: https://github.com/grind086/bevy_flickering_tiles/tree/main

Just jiggle the camera around a little and you should see the seams show up.

simplescreenrecorder-2025-12-23_15.05.35.webm

[hukasu]

Is TilemapChunk on 0.17.3 using flat texture or stacked 2d texture?

[grind086]

Stacked 2d