Ringing around pre-rasterized circles. #5810
Description
Describe the bug:
Rendering darker circles on a brighter background can lead to "ringing" artifacts, where the outermost pixels of the circle are brighter than both the background and the circle. The artifact only shows when "Speed up filled circles with pre-rasterization" is enabled in the Tesselation Options (default).
Some details:
- Circle fill is
rgb(200,200,200) - Background fill is
rgb(220,220,220) - Circle is rendered WITHOUT any border.
- The observed ring is not just perceptual. Checked with MacOS color picker, and some pixels are
rgb(230,230,230).
**
Minimal Repro Example:
**#[derive(Default)]
struct ExampleApp {}
impl eframe::App for ExampleApp {
fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
// Tesselation Options GUI.
egui::containers::SidePanel::left("left").show(ctx, |ui| {
let mut options = ui.ctx().tessellation_options(|options| options.clone());
ui.add(&mut options);
ui.ctx()
.tessellation_options_mut(|target| *target = options);
});
// Problematic dots/circles.
egui::CentralPanel::default()
.frame(egui::Frame::new())
.show(ctx, |ui| {
ui.painter().rect_filled(
ui.clip_rect(),
egui::CornerRadius::ZERO,
egui::Color32::from_rgb(220, 220, 220),
);
for x in 1..20 {
for y in 1..20 {
ui.painter().circle_filled(
ui.clip_rect().left_top() + egui::vec2(x as f32 * 10.0, y as f32 * 10.0),
1.5,
egui::Color32::from_rgb(200, 200, 200),
);
}
}
});
}
}
fn main() -> eframe::Result {
env_logger::init();
eframe::run_native(
"Bug Repro",
Default::default(),
Box::new(|_cc| Ok(Box::<ExampleApp>::default())),
)
}
Expected behavior
No ringing. Same visuals independent of whether pre-rasterization is enabled.
Screenshots
Bad:
Expected:
Closeup:
Desktop :
- OSX, native
Additional context
This bears some similarities to #5751, but in a more controlled environment, given that an egui-internal texture is involved.