Fix blocky artifacts in area aa
The numerical robustness work for multisampled aa was not carried over to the area version. This patch changes the computation of y_edge in the tiling stage so that rendering using area antialiasing in fine will match the multisampled case. See the linked bug for a diagram which explains the cases.
Fixes #393
diff --git a/shader/path_tiling.wgsl b/shader/path_tiling.wgsl
index 1e5ea17..abfa447 100644
--- a/shader/path_tiling.wgsl
+++ b/shader/path_tiling.wgsl
@@ -122,9 +122,9 @@
}
// See comments in CPU version of shader
var y_edge = 1e9;
- if xy0.x == tile_xy.x {
+ if xy0.x == tile_xy.x && xy1.x != tile_xy.x && xy0.y != tile_xy.y {
y_edge = xy0.y;
- } else if xy1.x == tile_xy.x {
+ } else if xy1.x == tile_xy.x && xy1.y != tile_xy.y {
y_edge = xy1.y;
}
if !is_down {
diff --git a/src/cpu_shader/path_tiling.rs b/src/cpu_shader/path_tiling.rs
index 56bc2b4..6b8a941 100644
--- a/src/cpu_shader/path_tiling.rs
+++ b/src/cpu_shader/path_tiling.rs
@@ -118,12 +118,11 @@
if !is_down {
(xy0, xy1) = (xy1, xy0);
}
- // TODO: figure out what to if both xy0 and xy1 are at left edge
- // Also TODO (part of move to 8 byte encoding for segments): don't store y_edge at all,
+ // TODO (part of move to 8 byte encoding for segments): don't store y_edge at all,
// resolve this in fine.
- let y_edge = if xy0.x == tile_xy.x {
+ let y_edge = if xy0.x == tile_xy.x && xy1.x != tile_xy.x && xy0.y != tile_xy.y {
xy0.y
- } else if xy1.x == tile_xy.x {
+ } else if xy1.x == tile_xy.x && xy1.y != tile_xy.y {
xy1.y
} else {
1e9
