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Tessellate: Implement precomputed vertices for rounding #1507

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Tessellate: Implement precomputed vertices for rounding #1507

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4fb0b85
Tessellate: Implement precomputed vertices for rounding
dbuch Apr 13, 2022
3d58ff5
adapt to code review
dbuch Apr 17, 2022
27d2d82
silence clippy
emilk Apr 30, 2022
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144 changes: 131 additions & 13 deletions epaint/src/tessellator.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -192,6 +192,117 @@ pub mod path {

use super::*;

mod precomputed_quadrants {
use emath::{vec2, Vec2};

pub const QUADRANTS_0_5: [[Vec2; 3]; 4] = [
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// quadrant 0: right bottom
[
vec2(1.000000, 0.000000),
vec2(0.707107, 0.707107),
vec2(-0.000000, 1.000000)
],
// quadrant 1: left bottom
[
vec2(-0.000000, 1.000000),
vec2(-0.707107, 0.707107),
vec2(-1.000000, -0.000000),
],
// quadrant 2: left top
[
vec2(-1.000000, -0.000000),
vec2(-0.707107, -0.707107),
vec2(0.000000, -1.000000),
],
// quadrant 3: right top
[
vec2(0.000000, -1.000000),
vec2(0.707107, -0.707107),
vec2(1.000000, 0.000000),
],
];

pub const QUADRANTS_5_10: [[Vec2; 5]; 4] = [
// quadrant 0: right bottom
[
vec2(1.000000, 0.000000),
vec2(0.923880, 0.382683),
vec2(0.707107, 0.707107),
vec2(0.382683, 0.923880),
vec2(-0.000000, 1.000000),
],
// quadrant 1: left bottom
[
vec2(-0.000000, 1.000000),
vec2(-0.382684, 0.923880),
vec2(-0.707107, 0.707107),
vec2(-0.923880, 0.382683),
vec2(-1.000000, -0.000000),
],
// quadrant 2: left top
[
vec2(-1.000000, -0.000000),
vec2(-0.923880, -0.382683),
vec2(-0.707107, -0.707107),
vec2(-0.382684, -0.923880),
vec2(0.000000, -1.000000),
],
// quadrant 3: right top
[
vec2(0.000000, -1.000000),
vec2(0.382684, -0.923879),
vec2(0.707107, -0.707107),
vec2(0.923880, -0.382683),
vec2(1.000000, 0.000000),
],
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Instead of having the four quadrants in separate array, we could just have all the circle vertices in circular order, and just slice into it. That way we could reuse the same vertices for circles too! It can wait for a separate PR though if you want.

];

pub const QUADRANTS_10_20: [[Vec2; 7]; 4] = [
// quadrant 0: right bottom
[
vec2(1.000000, 0.000000),
vec2(0.965926, 0.258819),
vec2(0.866025, 0.500000),
vec2(0.707107, 0.707107),
vec2(0.500000, 0.866025),
vec2(0.258819, 0.965926),
vec2(-0.000000, 1.000000),
],
// quadrant 1: left bottom
[
vec2(-0.000000, 1.000000),
vec2(-0.258819, 0.965926),
vec2(-0.500000, 0.866025),
vec2(-0.707107, 0.707107),
vec2(-0.866025, 0.500000),
vec2(-0.965926, 0.258819),
vec2(-1.000000, -0.000000),
],
// quadrant 2: left top
[
vec2(-1.000000, -0.000000),
vec2(-0.965926, -0.258819),
vec2(-0.866026, -0.500000),
vec2(-0.707107, -0.707107),
vec2(-0.500000, -0.866025),
vec2(-0.258819, -0.965926),
vec2(0.000000, -1.000000),
],
// quadrant 3: right top
[
vec2(0.000000, -1.000000),
vec2(0.258819, -0.965926),
vec2(0.500000, -0.866025),
vec2(0.707107, -0.707107),
vec2(0.866025, -0.500000),
vec2(0.965926, -0.258819),
vec2(1.000000, 0.000000),
],
];
}

use precomputed_quadrants::*;

/// overwrites existing points
pub fn rounded_rectangle(path: &mut Vec<Pos2>, rect: Rect, rounding: Rounding) {
path.clear();
Expand Down Expand Up @@ -236,19 +347,26 @@ pub mod path {
// - quadrant 3: right top
// * angle 4 * TAU / 4 = right
pub fn add_circle_quadrant(path: &mut Vec<Pos2>, center: Pos2, radius: f32, quadrant: f32) {
// TODO: optimize with precalculated vertices for some radii ranges

let n = (radius * 0.75).round() as i32; // TODO: tweak a bit more
let n = n.clamp(2, 32);
const RIGHT_ANGLE: f32 = TAU / 4.0;
path.reserve(n as usize + 1);
for i in 0..=n {
let angle = remap(
i as f32,
0.0..=n as f32,
quadrant * RIGHT_ANGLE..=(quadrant + 1.0) * RIGHT_ANGLE,
);
path.push(center + radius * Vec2::angled(angle));
if radius == 0.0 {
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path.push(center);
} else if radius <= 5.0 {
let quadrant_vertices = QUADRANTS_0_5[quadrant as usize];
path.reserve(quadrant_vertices.len());
quadrant_vertices
.iter()
.for_each(|v| path.push(center + radius * *v));
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} else if radius > 5.0 && radius <= 10.0 {
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let quadrant_vertices = QUADRANTS_5_10[quadrant as usize];
path.reserve(quadrant_vertices.len());
quadrant_vertices
.iter()
.for_each(|v| path.push(center + radius * *v));
} else {
let quadrant_vertices = QUADRANTS_10_20[quadrant as usize];
path.reserve(quadrant_vertices.len());
quadrant_vertices
.iter()
.for_each(|v| path.push(center + radius * *v));
}
}

Expand Down