bevy/crates
Ida "Iyes 60afec2a00
Fix 2D looking blurry at odd window sizes (#13440)
# Objective

This is a long-standing bug that I have experienced since many versions
of Bevy ago, possibly forever. Today I finally wanted to report it, but
the fix was so easy that I just went and fixed it. :)

The problem is that 2D graphics looks blurry at odd-sized window
resolutions. This is with the **default** 2D camera configuration! The
issue will also manifest itself with any Orthographic Projection with
`ScalingMode::WindowSize` where the viewport origin is not at one of the
corners, such as the default where the origin point is at the center.

The issue happens because the Bevy orthographic projection origin point
is specified as a fraction to be multiplied by the size. For example,
the default (origin at center) is `(0.5, 0.5)`. When this value is
multiplied by the window size, it can result in fractional values for
the actual origin of the projection, thus placing the camera "between
pixels" and misaligning the entire pixel grid.

With the default value, this happens at odd-numbered window resolutions.
It is very easy to reproduce the issue by running any Bevy 2D app with a
resizable window, and slowly resizing the window pixel by pixel. As you
move the mouse to resize the window, you can see how the 2D graphics
inside the window alternate between "crisp, blurry, crisp, blurry, ...".
If you change the projection's origin to be at the corner (say, `(0.0,
0.0)`) and run the app again, the graphics always looks crisp,
regardless of window size.

Here are screenshots from **before** this PR, to illustrate the issue:

Even window size:

![Screenshot_20240520_165304](https://github.com/bevyengine/bevy/assets/40234599/52619281-cf5f-490e-b85e-22bc5f9af737)

Odd window size:

![Screenshot_20240520_165320](https://github.com/bevyengine/bevy/assets/40234599/27a3624c-f39e-4493-ade9-ca3533802083)


## Solution

The solution is easy: just round the computed origin values for the
projection.

To make it work reliably for the general case, I decided to:
- Only do it for `ScalingMode::WindowSize`, as it doesn't make sense for
other scaling modes.
- Round to the nearest multiple of the pixel scale, if it is not 1.0.
This ensures the "pixels" stay aligned even if scaled.

## Testing

I ran Bevy's examples as well as my own projects to ensure things look
correct. I set different values for the pixel scale to test the rounding
behavior and played around with resizing the window to verify that
everything is consistent.

---

## Changelog

Fixed:
- Orthographic projection now rounds the origin point if computed from
screen pixels, so that 2D graphics do not appear blurry at odd window
sizes.
2024-05-22 02:59:40 +00:00
..
bevy_a11y Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_animation Remove ClampColor (#13307) 2024-05-10 13:15:56 +00:00
bevy_app Deprecate dynamic plugins (#13080) 2024-05-20 20:01:28 +00:00
bevy_asset Add more load_direct implementations (#13415) 2024-05-21 18:32:00 +00:00
bevy_audio Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_color Implement Color Operations for Color (#13285) 2024-05-14 10:15:47 +00:00
bevy_core Determine msrv for every standalone bevy_* crate. (#13211) 2024-05-13 18:26:41 +00:00
bevy_core_pipeline Make render phases render world resources instead of components. (#13277) 2024-05-21 18:23:04 +00:00
bevy_derive Deprecate dynamic plugins (#13080) 2024-05-20 20:01:28 +00:00
bevy_dev_tools #12502 Remove limit on RenderLayers. (#13317) 2024-05-16 16:15:47 +00:00
bevy_diagnostic Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_dylib Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_dynamic_plugin Deprecate dynamic plugins (#13080) 2024-05-20 20:01:28 +00:00
bevy_ecs Implement a SystemBuilder for building SystemParams (#13123) 2024-05-22 00:58:37 +00:00
bevy_encase_derive Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_gilrs Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_gizmos Inconsistent segments/resolution naming (#13438) 2024-05-21 18:42:59 +00:00
bevy_gltf fix normals computation for gltf (#13396) 2024-05-18 12:07:27 +00:00
bevy_hierarchy Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_input Separate state crate (#13216) 2024-05-09 18:06:05 +00:00
bevy_internal Separate state crate (#13216) 2024-05-09 18:06:05 +00:00
bevy_log Improve tracing layer customization (#13159) 2024-05-12 21:16:56 +00:00
bevy_macro_utils Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_math Add slerp function for Dir2, Dir3, Dir3A (#13451) 2024-05-21 21:13:32 +00:00
bevy_mikktspace Determine msrv for every standalone bevy_* crate. (#13211) 2024-05-13 18:26:41 +00:00
bevy_pbr Make render phases render world resources instead of components. (#13277) 2024-05-21 18:23:04 +00:00
bevy_ptr Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_reflect bevy_reflect: Custom attributes (#11659) 2024-05-20 19:30:21 +00:00
bevy_render Fix 2D looking blurry at odd window sizes (#13440) 2024-05-22 02:59:40 +00:00
bevy_scene Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_sprite Make render phases render world resources instead of components. (#13277) 2024-05-21 18:23:04 +00:00
bevy_state Revert "Add on_unimplemented Diagnostics to Most Public Traits" (#13413) 2024-05-17 17:00:43 +00:00
bevy_tasks multi_threaded feature rename (#12997) 2024-05-06 20:49:32 +00:00
bevy_text Add doc comments explaining the different behaviours of alignment and Anchor with text_2d (#8022) 2024-05-12 21:42:04 +00:00
bevy_time Adds doc note that Timer and Stopwatch must be progressed manually (#13441) 2024-05-20 19:46:25 +00:00
bevy_transform Use Dir3 for local axis methods in GlobalTransform (#13264) 2024-05-06 20:52:05 +00:00
bevy_ui Fix UI elements randomly not appearing after #13277. (#13462) 2024-05-21 22:06:25 +00:00
bevy_utils Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00
bevy_window Ensure clean exit (#13236) 2024-05-12 15:56:01 +00:00
bevy_winit Ensure clean exit (#13236) 2024-05-12 15:56:01 +00:00