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OrthographicProjection: place origin at integer pixel with WindowSize scaling mode (#4085)

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# Objective

One way to avoid texture atlas bleeding is to ensure that every vertex is
placed at an integer pixel coordinate. This is a particularly appealing
solution for regular structures like tile maps.

Doing so is currently harder than necessary when the WindowSize scaling
mode and Center origin are used: For odd window width or height, the
origin of the coordinate system is placed in the middle of a pixel at
some .5 offset.

## Solution

Avoid this issue by rounding the half width and height values.
This commit is contained in:
Matthias Schiffer 2022-05-30 15:14:12 +00:00
parent d353fbc6ea
commit 5256561b7a
1 changed files with 6 additions and 4 deletions
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10
crates/bevy_render/src/camera/projection.rs
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@ -104,12 +104,14 @@ impl CameraProjection for OrthographicProjection {
fn update(&mut self, width: f32, height: f32) { fn update(&mut self, width: f32, height: f32) {
match (&self.scaling_mode, &self.window_origin) { match (&self.scaling_mode, &self.window_origin) {
(ScalingMode::WindowSize, WindowOrigin::Center) => { (ScalingMode::WindowSize, WindowOrigin::Center) => {
let half_width = width / 2.0; let half_width = (width / 2.0).round();
let half_height = height / 2.0; let half_height = (height / 2.0).round();
self.left = -half_width; // Assign left and bottom such that (right-left)==width and (top-bottom)==height
// still hold with with rounded half_width and half_height
self.left = half_width - width;
self.right = half_width; self.right = half_width;
self.top = half_height; self.top = half_height;
self.bottom = -half_height; self.bottom = half_height - height;
} }
(ScalingMode::WindowSize, WindowOrigin::BottomLeft) => { (ScalingMode::WindowSize, WindowOrigin::BottomLeft) => {
self.left = 0.0; self.left = 0.0;