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Anti-alias path ends (#893)

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Closes https://github.com/emilk/egui/issues/876
This commit is contained in:
Emil Ernerfeldt 2021-11-14 17:23:51 +01:00 committed by GitHub
parent a0b635dc21
commit 5fee6b7bc5
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2 changed files with 110 additions and 26 deletions
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1
epaint/CHANGELOG.md
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@ -5,6 +5,7 @@ All notable changes to the epaint crate will be documented in this file.
## Unreleased
* `Rgba` now implements `Hash` ([#886](https://github.com/emilk/egui/pull/886)).
* Anti-alias path ends ([#893](https://github.com/emilk/egui/pull/893)).
## 0.15.0 - 2021-10-24

101
epaint/src/tessellator.rs
View file

@ -377,11 +377,12 @@ fn stroke_path(
options: &TessellationOptions,
out: &mut Mesh,
) {
if stroke.width <= 0.0 || stroke.color == Color32::TRANSPARENT {
let n = path.len() as u32;
if stroke.width <= 0.0 || stroke.color == Color32::TRANSPARENT || n < 2 {
return;
}
let n = path.len() as u32;
let idx = out.vertices.len() as u32;
if options.anti_alias {
@ -426,8 +427,7 @@ fn stroke_path(
i0 = i1;
}
} else {
// thick line
// TODO: line caps for really thick lines?
// thick anti-aliased line
/*
We paint the line using four edges: outer, inner, inner, outer
@ -439,14 +439,16 @@ fn stroke_path(
. |-----| inner_rad
*/
let inner_rad = 0.5 * (stroke.width - options.aa_size);
let outer_rad = 0.5 * (stroke.width + options.aa_size);
match path_type {
PathType::Closed => {
out.reserve_triangles(6 * n as usize);
out.reserve_vertices(4 * n as usize);
let mut i0 = n - 1;
for i1 in 0..n {
let connect_with_previous = path_type == PathType::Closed || i1 > 0;
let inner_rad = 0.5 * (stroke.width - options.aa_size);
let outer_rad = 0.5 * (stroke.width + options.aa_size);
let p1 = &path[i1 as usize];
let p = p1.pos;
let n = p1.normal;
@ -455,7 +457,6 @@ fn stroke_path(
out.colored_vertex(p - n * inner_rad, color_inner);
out.colored_vertex(p - n * outer_rad, color_outer);
if connect_with_previous {
out.add_triangle(idx + 4 * i0 + 0, idx + 4 * i0 + 1, idx + 4 * i1 + 0);
out.add_triangle(idx + 4 * i0 + 1, idx + 4 * i1 + 0, idx + 4 * i1 + 1);
@ -464,11 +465,93 @@ fn stroke_path(
out.add_triangle(idx + 4 * i0 + 2, idx + 4 * i0 + 3, idx + 4 * i1 + 2);
out.add_triangle(idx + 4 * i0 + 3, idx + 4 * i1 + 2, idx + 4 * i1 + 3);
}
i0 = i1;
}
}
PathType::Open => {
// Anti-alias the ends by extruding the outer edge and adding
// two more triangles to each end:
// | aa | | aa |
// _________________ ___
// | \ added / | aa_size
// | \ ___p___ / | ___
// | | | |
// | | opa | |
// | | que | |
// | | | |
// (in the future it would be great with an option to add a circular end instead)
out.reserve_triangles(6 * n as usize + 4);
out.reserve_vertices(4 * n as usize);
{
let end = &path[0];
let p = end.pos;
let n = end.normal;
let back_extrude = n.rot90() * options.aa_size;
out.colored_vertex(p + n * outer_rad + back_extrude, color_outer);
out.colored_vertex(p + n * inner_rad, color_inner);
out.colored_vertex(p - n * inner_rad, color_inner);
out.colored_vertex(p - n * outer_rad + back_extrude, color_outer);
out.add_triangle(idx + 0, idx + 1, idx + 2);
out.add_triangle(idx + 0, idx + 2, idx + 3);
}
let mut i0 = 0;
for i1 in 1..n - 1 {
let point = &path[i1 as usize];
let p = point.pos;
let n = point.normal;
out.colored_vertex(p + n * outer_rad, color_outer);
out.colored_vertex(p + n * inner_rad, color_inner);
out.colored_vertex(p - n * inner_rad, color_inner);
out.colored_vertex(p - n * outer_rad, color_outer);
out.add_triangle(idx + 4 * i0 + 0, idx + 4 * i0 + 1, idx + 4 * i1 + 0);
out.add_triangle(idx + 4 * i0 + 1, idx + 4 * i1 + 0, idx + 4 * i1 + 1);
out.add_triangle(idx + 4 * i0 + 1, idx + 4 * i0 + 2, idx + 4 * i1 + 1);
out.add_triangle(idx + 4 * i0 + 2, idx + 4 * i1 + 1, idx + 4 * i1 + 2);
out.add_triangle(idx + 4 * i0 + 2, idx + 4 * i0 + 3, idx + 4 * i1 + 2);
out.add_triangle(idx + 4 * i0 + 3, idx + 4 * i1 + 2, idx + 4 * i1 + 3);
i0 = i1;
}
{
let i1 = n - 1;
let end = &path[i1 as usize];
let p = end.pos;
let n = end.normal;
let back_extrude = -n.rot90() * options.aa_size;
out.colored_vertex(p + n * outer_rad + back_extrude, color_outer);
out.colored_vertex(p + n * inner_rad, color_inner);
out.colored_vertex(p - n * inner_rad, color_inner);
out.colored_vertex(p - n * outer_rad + back_extrude, color_outer);
out.add_triangle(idx + 4 * i0 + 0, idx + 4 * i0 + 1, idx + 4 * i1 + 0);
out.add_triangle(idx + 4 * i0 + 1, idx + 4 * i1 + 0, idx + 4 * i1 + 1);
out.add_triangle(idx + 4 * i0 + 1, idx + 4 * i0 + 2, idx + 4 * i1 + 1);
out.add_triangle(idx + 4 * i0 + 2, idx + 4 * i1 + 1, idx + 4 * i1 + 2);
out.add_triangle(idx + 4 * i0 + 2, idx + 4 * i0 + 3, idx + 4 * i1 + 2);
out.add_triangle(idx + 4 * i0 + 3, idx + 4 * i1 + 2, idx + 4 * i1 + 3);
// The extension:
out.add_triangle(idx + 4 * i1 + 0, idx + 4 * i1 + 1, idx + 4 * i1 + 2);
out.add_triangle(idx + 4 * i1 + 0, idx + 4 * i1 + 2, idx + 4 * i1 + 3);
}
}
}
}
} else {
// not anti-aliased:
out.reserve_triangles(2 * n as usize);
out.reserve_vertices(2 * n as usize);