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Improve the anti-aliasing of filled paths with sharp corners

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This comes at the cost of these corners sometimes becoming badly
extruded instead. The sharper the corner, the bigger the problem.

A proper fix will have to wait for later.

Part of https://github.com/emilk/egui/issues/1226
This commit is contained in:
Emil Ernerfeldt 2022-02-19 20:42:42 +01:00
parent b8fbbf7d62
commit e49245fae5
2 changed files with 17 additions and 1 deletions
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1
epaint/CHANGELOG.md
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@ -12,6 +12,7 @@ All notable changes to the epaint crate will be documented in this file.
* Added `Shape::dashed_line_many` ([#1027](https://github.com/emilk/egui/pull/1027)).
* Replaced `corner_radius: f32` with `rounding: Rounding`, allowing per-corner rounding settings ([#1206](https://github.com/emilk/egui/pull/1206)).
* Fix anti-aliasing of filled paths with counter-clockwise winding order.
* Improve the anti-aliasing of filled paths with sharp corners, at the cost of these corners sometimes becoming badly extruded instead (see https://github.com/emilk/egui/issues/1226).
## 0.16.0 - 2021-12-29

17
epaint/src/tessellator.rs
View file

@ -133,9 +133,20 @@ impl Path {
let normal = (n0 + n1) / 2.0;
let length_sq = normal.length_sq();
// We can't just cut off corners for filled shapes like this,
// because the feather will both expand and contract the corner along the provided normals
// to make sure it doesn't grow, and the shrinking will make the inner points cross each other.
//
// A better approach is to shrink the vertices in by half the feather-width here
// and then only expand during feathering.
//
// See https://github.com/emilk/egui/issues/1226
const CUT_OFF_SHARP_CORNERS: bool = false;
let right_angle_length_sq = 0.5;
let sharper_than_a_right_angle = length_sq < right_angle_length_sq;
if sharper_than_a_right_angle {
if CUT_OFF_SHARP_CORNERS && sharper_than_a_right_angle {
// cut off the sharp corner
let center_normal = normal.normalized();
let n0c = (n0 + center_normal) / 2.0;
@ -394,9 +405,13 @@ fn fill_closed_path(
let color_outer = Color32::TRANSPARENT;
let idx_inner = out.vertices.len() as u32;
let idx_outer = idx_inner + 1;
// The fill:
for i in 2..n {
out.add_triangle(idx_inner + 2 * (i - 1), idx_inner, idx_inner + 2 * i);
}
// The feathering:
let mut i0 = n - 1;
for i1 in 0..n {
let p1 = &path[i1 as usize];