migrations/egui
1
0
Fork 0
mirror of https://github.com/emilk/egui.git synced 2026-08-30 21:30:03 -04:00
Code Activity

Add RectShape::blur_width to implement shadows (#4267)

Browse Source 
This is mostly a refactor, but has some performance benefits:
* We (re)use the same tessellator as for everything else, leading to
less allocations
* We cull shapes before rendering them

Adding `RectShape::blur_width` means it can also be used for other
effects, such as glow.
This commit is contained in:
Emil Ernerfeldt
2024-03-29 20:29:42 +01:00
committed by GitHub
parent 73dbfd689b
commit a541e021aa
7 changed files with 62 additions and 51 deletions
Download Patch File Download Diff File Expand all files Collapse all files

42
crates/epaint/src/shadow.rs
View File

@@ -1,5 +1,3 @@
use emath::NumExt as _;
use super::*;
/// The color and fuzziness of a fuzzy shape.
@@ -37,11 +35,10 @@ impl Shadow {
color: Color32::TRANSPARENT,
};
pub fn tessellate(&self, rect: Rect, rounding: impl Into<Rounding>) -> Mesh {
/// The argument is the rectangle of the shadow caster.
pub fn as_shape(&self, rect: Rect, rounding: impl Into<Rounding>) -> RectShape {
// tessellator.clip_rect = clip_rect; // TODO(emilk): culling
use crate::tessellator::*;
let Self {
offset,
blur,
@@ -50,40 +47,9 @@ impl Shadow {
} = *self;
let rect = rect.translate(offset).expand(spread);
let rounding = rounding.into() + Rounding::same(spread.abs());
// We simulate a blurry shadow by tessellating a solid rectangle using a very large feathering.
// Feathering is usually used to make the edges of a shape softer for anti-aliasing.
// The tessellator can't handle blurring/feathering larger than the smallest side of the rect.
// Thats because the tessellator approximate very thin rectangles as line segments,
// and these line segments don't have rounded corners.
// When the feathering is small (the size of a pixel), this is usually fine,
// but here we have a huge feathering to simulate blur,
// so we need to avoid this optimization in the tessellator,
// which is also why we add this rather big epsilon:
let eps = 0.1;
let blur = blur.at_most(rect.size().min_elem() - eps).at_least(0.0);
// TODO(emilk): if blur <= 0, return a simple `Shape::Rect` instead of using the tessellator
let rounding_expansion = spread.abs() + 0.5 * blur;
let rounding = rounding.into() + Rounding::same(rounding_expansion);
let rect = RectShape::filled(rect, rounding, color);
let pixels_per_point = 1.0; // doesn't matter here
let font_tex_size = [1; 2]; // unused since we are not tessellating text.
let mut tessellator = Tessellator::new(
pixels_per_point,
TessellationOptions {
feathering: true,
feathering_size_in_pixels: blur * pixels_per_point,
..Default::default()
},
font_tex_size,
vec![],
);
let mut mesh = Mesh::default();
tessellator.tessellate_rect(&rect, &mut mesh);
mesh
RectShape::filled(rect, rounding, color).with_blur_width(blur)
}
/// How much larger than the parent rect are we in each direction?