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Improve smudge tool

This commit is contained in:
Skyler Lehmkuhl 2026-03-06 06:03:33 -05:00
parent 553cc383d5
commit bff3d660d6
4 changed files with 115 additions and 34 deletions
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5
lightningbeam-ui/lightningbeam-core/src/brush_engine.rs
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@ -461,7 +461,10 @@ impl BrushEngine {
if matches!(base_blend, RasterBlendMode::Smudge) {
let ndx = dx / seg_len;
let ndy = dy / seg_len;
let smudge_dist = radius2 * bs.smudge_radius_log.exp();
// strength=1.0 → sample from 1 dab back (drag pixels with us).
// strength=0.0 → sample from current position (no change).
// smudge_radius_log is repurposed as a linear [0,1] strength value here.
let smudge_dist = spacing_px * bs.smudge_radius_log.clamp(0.0, 1.0);
push_dab(&mut dabs, &mut bbox,
ex, ey, radius2, opacity2, cr, cg, cb,
ndx, ndy, smudge_dist);

105
lightningbeam-ui/lightningbeam-editor/src/gpu_brush.rs
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@ -276,15 +276,9 @@ impl GpuBrushEngine {
/// Dispatch the brush compute shader for `dabs` onto the canvas of `keyframe_id`.
///
/// All dabs for the frame are batched into a single GPU dispatch:
/// 1. Copy the FULL canvas src→dst (so dst has all previous dabs).
/// 2. Upload all dabs as one storage buffer.
/// 3. Dispatch the compute shader once over the union bounding box.
/// 4. Swap once.
///
/// Batching is required for correctness: a per-dab copy of only the dab's
/// bounding box would leave all other previous dabs missing from dst after swap,
/// causing every other dab to flicker in/out.
/// Paint/erase dabs are batched in a single GPU dispatch with a full canvas copy.
/// Smudge dabs are dispatched sequentially (one per dab) with a bbox-only copy
/// so each dab reads the canvas state written by the previous dab.
///
/// If `dabs` is empty, does nothing.
pub fn render_dabs(
@ -298,12 +292,65 @@ impl GpuBrushEngine {
canvas_h: u32,
) {
if dabs.is_empty() { return; }
// Smudge dabs must be applied one at a time so each dab reads the canvas
// state written by the previous dab. Use bbox-only copies (union of current
// and previous dab) to avoid an expensive full-canvas copy per dab.
let is_smudge = dabs.first().map(|d| d.blend_mode == 2).unwrap_or(false);
if is_smudge {
let mut prev_bbox: Option<(i32, i32, i32, i32)> = None;
for dab in dabs {
let r = dab.radius + 1.0;
let cur_bbox = (
(dab.x - r).floor() as i32,
(dab.y - r).floor() as i32,
(dab.x + r).ceil() as i32,
(dab.y + r).ceil() as i32,
);
// Expand copy region to include the previous dab's bbox so the
// pixels it wrote are visible as the source for this dab's smudge.
let copy_bbox = match prev_bbox {
Some(pb) => (cur_bbox.0.min(pb.0), cur_bbox.1.min(pb.1),
cur_bbox.2.max(pb.2), cur_bbox.3.max(pb.3)),
None => cur_bbox,
};
self.render_dabs_batch(device, queue, keyframe_id,
std::slice::from_ref(dab), cur_bbox, Some(copy_bbox), canvas_w, canvas_h);
prev_bbox = Some(cur_bbox);
}
} else {
self.render_dabs_batch(device, queue, keyframe_id, dabs, bbox, None, canvas_w, canvas_h);
}
}
/// Inner batch dispatch.
///
/// `dispatch_bbox` — region dispatched to the compute shader (usually the union of all dab bboxes).
/// `copy_bbox` — region to copy src→dst before dispatch:
/// - `None` → copy the full canvas (required for paint/erase batches so
/// dabs outside the current frame's region are preserved).
/// - `Some(r)` → copy only region `r` (sufficient for sequential smudge dabs
/// because both textures hold identical data outside previously
/// touched regions, so no full copy is needed).
fn render_dabs_batch(
&mut self,
device: &wgpu::Device,
queue: &wgpu::Queue,
keyframe_id: Uuid,
dabs: &[GpuDab],
dispatch_bbox: (i32, i32, i32, i32),
copy_bbox: Option<(i32, i32, i32, i32)>,
canvas_w: u32,
canvas_h: u32,
) {
if dabs.is_empty() { return; }
let canvas = match self.canvases.get_mut(&keyframe_id) {
Some(c) => c,
None => return,
};
// Clamp the union bounding box to canvas bounds.
// Clamp the dispatch bounding box to canvas bounds.
let bbox = dispatch_bbox;
let x0 = bbox.0.max(0) as u32;
let y0 = bbox.1.max(0) as u32;
let x1 = (bbox.2 as u32).min(canvas_w);
@ -312,11 +359,18 @@ impl GpuBrushEngine {
let bbox_w = x1 - x0;
let bbox_h = y1 - y0;
// Step 1: Copy the ENTIRE canvas src→dst so dst starts with all previous dabs.
// A bbox-only copy would lose previous dabs outside this frame's region after swap.
// Step 1: Copy src→dst.
// For paint/erase batches (copy_bbox = None): copy the ENTIRE canvas so dst
// starts with all previous dabs — a bbox-only copy would lose dabs outside
// this frame's region after swap.
// For smudge (copy_bbox = Some(r)): copy only the union of the current and
// previous dab bboxes. Outside that region both textures hold identical
// data so no full copy is needed.
let mut copy_enc = device.create_command_encoder(
&wgpu::CommandEncoderDescriptor { label: Some("canvas_full_copy_encoder") },
&wgpu::CommandEncoderDescriptor { label: Some("canvas_copy_encoder") },
);
match copy_bbox {
None => {
copy_enc.copy_texture_to_texture(
wgpu::TexelCopyTextureInfo {
texture: canvas.src(),
@ -332,6 +386,31 @@ impl GpuBrushEngine {
},
wgpu::Extent3d { width: canvas_w, height: canvas_h, depth_or_array_layers: 1 },
);
}
Some(cb) => {
let cx0 = cb.0.max(0) as u32;
let cy0 = cb.1.max(0) as u32;
let cx1 = (cb.2 as u32).min(canvas_w);
let cy1 = (cb.3 as u32).min(canvas_h);
if cx1 > cx0 && cy1 > cy0 {
copy_enc.copy_texture_to_texture(
wgpu::TexelCopyTextureInfo {
texture: canvas.src(),
mip_level: 0,
origin: wgpu::Origin3d { x: cx0, y: cy0, z: 0 },
aspect: wgpu::TextureAspect::All,
},
wgpu::TexelCopyTextureInfo {
texture: canvas.dst(),
mip_level: 0,
origin: wgpu::Origin3d { x: cx0, y: cy0, z: 0 },
aspect: wgpu::TextureAspect::All,
},
wgpu::Extent3d { width: cx1 - cx0, height: cy1 - cy0, depth_or_array_layers: 1 },
);
}
}
}
queue.submit(Some(copy_enc.finish()));
// Step 2: Upload all dabs as a single storage buffer.

7
lightningbeam-ui/lightningbeam-editor/src/panes/infopanel.rs
View File

@ -329,10 +329,9 @@ impl InfopanelPane {
ui.add(egui::Slider::new(shared.smudge_radius, 1.0_f32..=200.0).logarithmic(true).suffix(" px"));
});
ui.horizontal(|ui| {
ui.label("Reach:");
ui.add(egui::Slider::new(shared.smudge_strength, 0.1_f32..=5.0)
.logarithmic(true)
.custom_formatter(|v, _| format!("{:.2}x", v)));
ui.label("Strength:");
ui.add(egui::Slider::new(shared.smudge_strength, 0.0_f32..=1.0)
.custom_formatter(|v, _| format!("{:.0}%", v * 100.0)));
});
ui.horizontal(|ui| {
ui.label("Hardness:");

2
lightningbeam-ui/lightningbeam-editor/src/panes/stage.rs
View File

@ -4812,7 +4812,7 @@ impl StagePane {
b.dabs_per_actual_radius = 0.0;
// strength controls how far behind the stroke to sample (smudge_dist multiplier).
// smudge_dist = radius * exp(smudge_radius_log), so log(strength) gives the ratio.
b.smudge_radius_log = shared.smudge_strength.ln();
b.smudge_radius_log = *shared.smudge_strength; // linear [0,1] strength
}
b
};