UV coordinates in Bevy

In Bevy, the vertical axis for the pixels of textures / images, and when sampling textures in a shader, points downwards, from top to bottom. The origin is at the top left.

This is consistent with how most image file formats store pixel data, and with how most graphics APIs work (including DirectX, Vulkan, Metal, WebGPU, but not OpenGL).

This is different from OpenGL (and frameworks based on it). If your prior experience is with these, you may find that the textures on your meshes are flipped vertically. You will have to reexport / regenerate your meshes in the correct UV format.

This is also inconsistent with the World-coordinate system used everywhere else in Bevy, where the Y axis points up.

If the images of your 2D sprites are flipped (for whatever reason), you can correct that using Bevy's sprite-flipping feature:

commands.spawn_bundle(SpriteBundle {
    sprite: Sprite {
        flip_y: true,
        flip_x: false,
        ..Default::default()
    },
    ..Default::default()
});