Make the data model use Item and List types universally, with nodes authored as rank-polymorphic kernels (#4335)

* Add rank polymorphism node audit classifying all 271 nodes * Implement StaticType for Item<T> * Generate Item and mapped List wire variants for nodes declaring an Item<T> primary input * Migrate nine nodes to Item element-wise kernels, dissolving the blending trait boilerplate * Document the Item kernel implementation and staging plan * Route Item<Vector> through TaggedValue::TypeDefault * Add executor integration tests covering the Item and List wire variants * Collapse element-wise Item/List wire pairs to the List form for conversion insertion * Migrate sixteen vector modifier nodes to Item element-wise kernels * Migrate Sample Image, Extend Image to Bounds, and Dehaze to Item element-wise kernels * Fix bevel_with_transform test to actually exercise the transform attribute * Implement From<T> for Item<T> * Register PromoteNode rank adapters wrapping bare values into Item wires * Insert PromoteNode adapters for Item/List wire pair fields in the preprocessor * Define a real promote node backing the PromoteNode registry identifiers * Zip ranked Item connectors by frame slot in the mapped element-wise variant * Register ItemToListNode singleton raise adapters * Resolve Item wires against List connectors by inserting promotion adapters at construction * Rank the Offset Points distance connector and prove mixed-rank resolution end-to-end * Implement Clampable for Item and List wires with per-variant clamp bounds * Rank the Round Corners radius connector, exercising hard bounds on a ranked wire * Implement ApplyTransform for Item * Add Item wire implementations to the Transform node, keeping rank-0 chains rank 0 * Detect element-wise nodes by lazy primary connectors declaring Output = Item * Convert Transform to an Item kernel with ranked parameters, delivering the broadcast milestone * Rename Apply Transform to Bake Transform, baking item transforms on Vector, DAffine2, and DVec2 * Promote bare wires onto Item connectors at resolution via WrapItemNode adapters * Rank the numeric, vector, and boolean parameters across the migrated element-wise nodes * Rank the enum, integer, and seed parameters, registering their rank adapters via a consolidated macro * Amend the audit with the DashPattern value type resolution * Migrate the string family to Item element-wise kernels * Unwrap Item wires into bare legacy connectors at resolution via UnwrapItemNode adapters * Shadow owned node parameters in bodies instead of mut in signatures * Migrate the math family and string measure nodes to Item element-wise kernels * Convert the comparison and clamp nodes to Item kernels, dropping unreachable &str rows * Flat-map expander kernels returning List under the mapped variant's frame * Migrate the expander nodes to Item kernels flat-mapping under the frame * Remove the unused peel_list helper * Rank the raster adjustment and blending kernels, recontextualizing shader nodes onto an Item stand-in Migrate the 16 adjustment nodes, Mix, Color Overlay, and Gradient Map from whole-List kernels to rank-0 Item kernels, letting the macro derive the List-mapped (zip) variants. Move the Adjust and Blend per-element seams off List onto the element types (add the Raster<CPU> impls, drop the now-dead List impls). Shader nodes keep their bodies verbatim: PerPixelAdjust re-emits the identical kernel against a transparent no_std Item stand-in, so every Item<T> connector and .element() call resolves to a zero-cost identity on the GPU while the uniform buffer stays bare repr(C). The macro peels Item off ranked uniform params, wraps the fetched texel and uniforms at the entry point, and unwraps the result. This drops the shader_node/Item incompatibility guard. Register rank adapters for the adjustment enums. * Update the rank polymorphism roadmap for the landed shader-node and adjustments chunk * Rename the GPU Item stand-in to ShaderItem, aliased as Item at its shader-node import sites * Flip the vector shape generators to emit rank-0 Item<Vector> The shape generators (Rectangle, Circle, Ellipse, Arc, Spiral, Polygon, Star, Arrow, Line, Grid, QR Code) each produced exactly one shape wrapped in a singleton List<Vector>. Emit Item<Vector> directly so they connect to the rank-0 content connector of the migrated Transform node. Downstream List consumers receive the value through the existing Item to List promotion. Relax the element-wise validation so a `()` (generator) primary may return Item<T> without being element-wise. Adapt the Repeat on Points test, which still takes a List content connector, by raising the generator's Item output through a singleton wrapper node. * Parse ranked Item<T> parameter defaults against the bare element type A ranked `Item<T>` parameter's default value is a bare, unranked `T` (promoted to the wire at resolution), but the preprocessor was handed the wrapped `Item<T>` type and could not parse the literal, flooding the console with warnings and dropping the defaults. Key the field's default_type metadata off the peeled element type for concrete ranked parameters, leaving generic `Item<T>` primaries and skip_impl nodes untouched. * Parse an element-wise primary's scalar default against the bare element type An element-wise node's primary reports its default_type as the List wire form so an unconnected primary defaults to an empty list. But when the primary carries a scalar `#[default]` (such as Root's radicand), that literal must parse as a bare element, not a List. Key the primary's default_type off the bare element type when it has a Default value source, keeping the List form otherwise. * Add the DashPattern value type for stroke dash sequences Introduce a rank-0 DashPattern value type (a Vec<f64> of alternating dash and gap lengths) so a stroke's dash pattern is a single frameable value rather than a rank-1 List<f64>. Register it as an auto-generated TaggedValue variant, parse its default from a comma or space separated string, and register its rank adapters. Not yet wired into the Stroke node. * Rank the Fill and Stroke nodes element-wise and give Stroke a DashPattern connector Migrate Fill and Stroke to element-wise Item<V> primaries (over Vector and Graphic element types) via a new element-level VectorItemMut trait, so styling one shape yields one shape and rank is preserved instead of promoting the input to a singleton List and emitting a List. The macro derives the List-mapped variant for genuine collections. Wire the Stroke dash sequence to the new rank-0 DashPattern value type, collapsing the old content x paint x dash cartesian and dropping the IntoF64Vec trait. Update the stroke properties dash widget, the drawing tool, and graph-operation plumbing to read and write DashPattern, and migrate legacy F64Array, F64, and String dash inputs on document open. Assign Colors stays a whole-collection node: each element's gradient position depends on its index among all siblings, which the element frame does not expose, so it keeps its List primary and the VectorListIterMut trait. * Register rank adapters for the ranked Stroke enum parameters The element-wise Stroke node ranks its align, cap, and paint order parameters as Item<StrokeAlign>, Item<StrokeCap>, and Item<PaintOrder>, but those enums lacked promotion adapters, so a bare default enum value could not be promoted to its Item wire and no Stroke variant resolved ("No construct found for node"). Register their rank adapters alongside StrokeJoin. * Display Item wires in the Data panel without a List's ID column Add a TableItemLayout impl for Item<T> and recognize Item wire types when introspecting graph data. An Item holds a single element, so it renders as a one-row table of the element plus its attributes with no leading index column, and it labels as its element type T rather than a List's T[]. Add ItemAttributeValues::get_any for the attribute widget dispatch. * Register MonitorNode for Item wire types so the Data panel introspects them directly Graph introspection wraps the inspected output in a generic MonitorNode typed to the wire. Without Item<T> monitor registrations, an Item<Vector> output could only be monitored after an Item to List promotion, so the Data panel captured and displayed a List<Vector> despite the connector being Item<Vector>. Register monitors for the Item types the element-wise nodes emit, and add the matching Data panel downcast entries. * Color and double Item/List wires and cleave layer-stack connectors in the node graph * Route wire color and rank through hidden nodes and refresh them on type changes * Rework the DashPattern connector conversions with element-wise promotion and an explicit reducer node * Rank the remaining value, context, aggregation, and transform nodes onto Item<T> wires * Back DashPattern with a List<f64> so the Data panel can introspect its lengths * Carry a single Item<T> through varargs so the Read context nodes emit Item<T> not List<T> * Relax rank validation for aggregation shapes, add element adapters, and match variants by fewest promotions * Rank the remaining bare and unnecessarily-List connectors across the node catalog * Add Graphic::None and the FillChoice paint value, making colors and gradients plain values * Rename GradientStops to Gradient and the legacy Gradient/Fill structs to LegacyGradient/LegacyFill * Restore generator frame-from-params ranking to the roadmap as a planned stage * Rename the ranked-field adapter identifier from PromoteNode to FieldAdapterNode to reflect its full contract * Unload only the wires whose displayed style changed when types update * Peel wire rank in the editor's semantic type checks so rank-0 layers are recognized * Restore the whole-List Transform variant so rank-1 content wires resolve again * Register the Item wire forms for the Memoize and Context Modification infrastructure nodes * Give every ranked connector a field adapter and add numeric cast variants for legacy wires * Key a ranked param's type default off its Item wire form when no literal default exists * Inherit the layer's content value when splicing a node into an empty chain * Migrate stale List-form TypeDefault inputs to the definition's current default * Generate the mapped wire variant only when the element-wise node has a frame source * Let a bare wire feed a List connector via a wrap-raise adapter, costed as two rank steps * Add a zip companion to the whole-List Transform so ranked List parameters pair per slot * Add the Sum, Average, Minimum, Maximum, Any, and All list reducers * Convert the measure family to element-wise Item kernels per the audit classification * Prefer the bare element value over the Item type default so ranked params keep their widgets * Rename GradientStopsUI to GradientUI * Split Fill's optional transform into a _has_transform bool and a ranked _transform matrix * Rename the migration-only OptionalDAffine2 TaggedValue to LegacyOptionalDAffine2 * Flow byte buffers as Item<Resource> instead of List<u8> across the byte nodes * Macro-generate the list-content wire variant, retiring the hand-written Transform-zip, Area, and Centroid companions * Let ()-primary generators take ranked params and frame over them via the mapped variant, ranking Circle's radius * Rank the vector shape generators' params to Item, adding a rank-aware input grab to the introspection harness * Rank the value, color, and text generator params to Item * Rank the raster, web-request, and context-reader generator params to Item * Fix the repeat and brush test wirings left behind by the param-ranking sweeps * Delete the vestigial Some, Unwrap Option, and Size Of debug nodes * Delete the Attach Attribute node, folding its role into Write Attribute * Add the Filter and Sort list companion nodes * Guard the removed-definition migration swap target with a test * Add the Box Corners value type in place of the rectangle corner radius list * Split Text to Vector's per-glyph mode into a Text to Vector Glyphs node * Rank the Combine Channels node's channel connectors to Item * Make Map Points an element-wise node * Delete the deprecated Upload Texture node * Update the implementation roadmap to reflect the landed stages * Let monitor introspection read rank-0 wires, locking in the layer coercion promotion path * Prefer the rank-0 default when disconnecting a rank-capable input * Make Path Modify an element-wise node * Wrap node paths in a NodeIdPath newtype so they flow as a single Item * Give Item<Raster<CPU>> a default so an unconnected Brush background resolves * Stop the Brush node from setting layer attributes its paint operation doesn't produce * Present-gate Flatten Path's adopted layer path like its fill and stroke * Gate carried layer attributes on static column presence, not runtime values * Give the remaining graphic Item<T> types a default so unconnected primaries resolve * Dispatch a ranked param's Properties widget from its rank-0 element type * Make Extract Transform an element-wise node, restoring the Origins to Polyline body * Rename Flatten Path to Combine Paths * Stamp Legacy Layer Extend's adopted layer path as a readable NodeIdPath * Drop the dead List<u8> and List<NodeId> wire rows * Rank Flatten Graphic's Fully Flatten toggle to Item * Update the implementation roadmap with the endgame scope * Make Combine Paths a reducer that collapses the whole frame into one path * Stop type-converter nodes from carrying the source's unrelated attributes * Format the Origins to Polyline regression test * Wrap the Brush node's trace in a BrushTrace newtype so it flows as one value * Make Switch a framed element-wise select, bundling whole collections * Widen and align element-type coverage across the list and graphic nodes * Register the compiler's cache chain pair for every ranked enum and newtype wire * Fix wire colors for Passthrough outputs, bundled lists, and bools, and widen list wires * Represent List wire types structurally with Type::List, replacing name-parsed rank promotion * Treat scope and data fields as environment, rank scope wires as Item, and feed the render boundary through a context vararg * Delete the vestigial Clone debug node * Reinstate Upload Texture as an element-wise node and fix the GPU variants' scope executor and rank adapters * Rename Combine Paths back to Flatten Path, deferring that rename to its own PR * Deduplicate the promotion adapter registrations into the field adapter macro * Rank Write Attribute's value connector to Item<AttributeValueDyn>, retiring the UnwrapItem bridge * Vertical wire styling * Store the editor layer path attribute as a bare NodeIdPath, not an Item<NodeIdPath> * Rank Context Modification's features connector to Item<ContextFeatures>, dropping the dead memoize row * Rank Path Modify's modification parameter to Item<Box<VectorModification>> * Rename the field adapter node family to input adapter * Drop the dead bare scalar rows from Context Modification's implementations list * Move the dynamic executor's test module into its own file * Drop the registry's unreachable bare rows for Memoize, the cache chain, and ConvertNode * Materialize stored TaggedValues as ranked Item wires at the source * Remove the bare-wire promotion and adapter machinery made dead by ranked value materialization * Plant the input adapter for List-only inputs, composing position conversion from standard rows * Consolidate Into/Convert conversions into the input adapter umbrella and rename the rank adapter identifiers * Fix grouped layers gaining a phantom None stack element from the FillChoice default hijacking every List<Graphic> disconnect * Enforce ranked node inputs in the macro, rejecting bare wire declarations * Remove the unit Context => () machinery rows, leaving () purely as the no-primary sentinel * Add a --signatures rank-audit mode to node-docs for the ranked-wire migration * Remove the node-docs --signatures rank-audit mode now that ranked wires are enforced * Migrate legacy no-color values on the Black & White, Color Overlay, and Empty Image color inputs * Rewrite the element-wise accessor wire type at the primary input, not raw index 0 * Register the cache chain for Resource wires, replacing the lone hand-written Monitor row * Gate the remaining Raster<GPU> registry rows behind the gpu feature * Let List<DVec2> wires erase to ListDyn for the attribute reader and element counter * Rename Extract Element to Item at Index, Count Elements to List Length, and Omit Element to Remove at Index * Store paint picks as plain color/gradient values, removing the FillChoice value type * Code review restructuring * Sort by the consumed sort_key attribute or natural element order, adding the Sort Key node * Remove the new list-combinator and reducer nodes to defer them to a follow-up PR * Parse Fill and Stroke color defaults through the paint wire's Graphic element * Emit ranked implementation-row default types structurally so their element TypeIds survive to default-literal parsing * Exempt the deliberate no-paint choice from the stale List-form TypeDefault migration * Migrate the legacy 4-input Fill directly to the split has-transform shape * Upgrade the demo artwork * Fix the valid AI review findings: Item eq/hash contract, table-era no-paint migration, quantize List rows, and other smaller issues * Remove the rank polymorphism working documents * Hash Item attribute values directly instead of debug-formatting them, speeding up cached evaluation * Replace the data panel's dead bare-wire downcast arms with full coverage of the ranked monitor row types * Derive PartialEq for Item now that attributes participate in equality * Extend the data panel's attribute dispatchers with the newly supported scalar and choice enum types * Add List monitor rows for the framed numeric conversion outputs so inspecting them resolves, with matching data panel arms
2026-10-04 16:58:11 +08:00 · 2026-09-08 16:03:01 +00:00
parent 296185b7fc
commit a708a54492
3257 changed files with 766342 additions and 1829 deletions
@@ -0,0 +1,30 @@
+[package]
+name = "brush-nodes"
+version = "0.1.0"
+edition = "2024"
+description = "Brush rendering nodes for Graphene"
+authors = ["Graphite Authors <contact@graphite.art>"]
+license = "MIT OR Apache-2.0"
+
+[features]
+default = ["serde"]
+serde = ["dep:serde", "core-types/serde", "raster-types/serde", "raster-nodes/serde"]
+
+[dependencies]
+# Local dependencies
+dyn-any = { workspace = true }
+core-types = { workspace = true }
+graphene-hash = { workspace = true }
+raster-types = { workspace = true }
+raster-nodes = { workspace = true }
+node-macro = { workspace = true }
+
+# Workspace dependencies
+glam = { workspace = true }
+
+# Optional workspace dependencies
+serde = { workspace = true, optional = true, features = ["derive"] }
+
+[dev-dependencies]
+# Workspace dependencies
+tokio = { workspace = true }
@@ -0,0 +1,493 @@
+use crate::brush_cache::BrushCache;
+use crate::brush_stroke::{BrushStroke, BrushStyle};
+use core_types::attribute::{Attr, BlendMode as BlendModeAttr, ClippingMask, EditorLayerPath, Opacity, OpacityFill, Transform as TransformAttr};
+use core_types::blending::BlendMode;
+use core_types::bounds::{BoundingBox, RenderBoundingBox};
+use core_types::color::{Alpha, Color, Pixel, Sample};
+use core_types::extent::{LevelIn, ListIn};
+use core_types::gpoll::{Extent, GPoll, GraphError, Interrupt};
+use core_types::list::{Item, List};
+use core_types::math::bbox::{AxisAlignedBbox, Bbox};
+use core_types::transform::Transform;
+use core_types::uuid::NodeId;
+use core_types::{ATTR_BLEND_MODE, ATTR_CLIPPING_MASK, ATTR_OPACITY, ATTR_OPACITY_FILL, ATTR_TRANSFORM};
+use core_types::{Ctx, ExtractIndex, InjectIndex};
+use glam::{DAffine2, DVec2};
+use raster_nodes::blending_nodes::blend_colors;
+use raster_nodes::std_nodes::{empty_image_core, extend_image_to_bounds_core};
+use raster_types::BitmapMut;
+use raster_types::Image;
+use raster_types::{CPU, Raster};
+
+#[derive(Clone, Copy, Debug, PartialEq, dyn_any::DynAny)]
+pub struct BrushStampGenerator<P: Pixel + Alpha> {
+	color: P,
+	feather_exponent: f32,
+	transform: DAffine2,
+}
+
+impl<P: Pixel + Alpha> Transform for BrushStampGenerator<P> {
+	fn transform(&self) -> DAffine2 {
+		self.transform
+	}
+}
+
+impl<P: Pixel + Alpha> Sample for BrushStampGenerator<P> {
+	type Pixel = P;
+
+	#[inline]
+	fn sample(&self, position: DVec2, area: DVec2) -> Option<P> {
+		let position = self.transform.inverse().transform_point2(position);
+		let area = self.transform.inverse().transform_vector2(area);
+		let aa_blur_radius = area.length() as f32 * 2.;
+		let center = DVec2::splat(0.5);
+
+		let distance = (position + area / 2. - center).length() as f32 * 2.;
+
+		let edge_opacity = 1. - (1. - aa_blur_radius).powf(self.feather_exponent);
+		let result = if distance < 1. - aa_blur_radius {
+			1. - distance.powf(self.feather_exponent)
+		} else if distance < 1. {
+			// TODO: Replace this with a proper analytical AA implementation
+			edge_opacity * ((1. - distance) / aa_blur_radius)
+		} else {
+			return None;
+		};
+
+		use core_types::color::Channel;
+		Some(self.color.multiplied_alpha(P::AlphaChannel::from_linear(result)))
+	}
+}
+
+/// Controls the brush shape with diameter and hardness, plus color and opacity (via flow).
+/// The feather exponent is calculated from hardness to determine edge softness.
+/// Used internally to create the brush texture before stamping it repeatedly along a stroke path.
+#[node_macro::node(category(""), skip_impl)]
+fn brush_stamp_generator(_: impl Ctx, #[unit(" px")] diameter: f64, color: Color, hardness: f64, flow: f64) -> BrushStampGenerator<Color> {
+	// Diameter
+	let radius = diameter / 2.;
+
+	// Hardness
+	let hardness = hardness / 100.;
+	let feather_exponent = 1. / (1. - hardness) as f32;
+
+	// Flow
+	let flow = flow / 100.;
+
+	// Color
+	let color = color.apply_opacity(flow as f32);
+
+	let transform = DAffine2::from_scale_angle_translation(DVec2::splat(diameter), 0., -DVec2::splat(radius));
+	BrushStampGenerator { color, feather_exponent, transform }
+}
+
+/// Used to efficiently paint brush strokes. Applies the same texture repeatedly at different positions with proper blending and boundary handling.
+#[node_macro::node(category(""), skip_impl)]
+fn blit<BlendFn: Fn(Color, Color) -> Color>(_: impl Ctx, mut target: List<Raster<CPU>>, texture: Raster<CPU>, positions: Vec<DVec2>, blend_mode: BlendFn) -> List<Raster<CPU>> {
+	if positions.is_empty() {
+		return target;
+	}
+
+	let (elements, transforms) = target.element_and_attribute_slices_mut::<DAffine2>(ATTR_TRANSFORM);
+	for (element, transform_attribute) in elements.iter_mut().zip(transforms.iter()) {
+		let target_width = element.width;
+		let target_height = element.height;
+		let target_size = DVec2::new(target_width as f64, target_height as f64);
+
+		let texture_size = DVec2::new(texture.width as f64, texture.height as f64);
+
+		let document_to_target = DAffine2::from_translation(-texture_size / 2.) * DAffine2::from_scale(target_size) * transform_attribute.inverse();
+
+		for position in &positions {
+			let start = document_to_target.transform_point2(*position).round();
+			let stop = start + texture_size;
+
+			// Half-open integer ranges [start, stop).
+			let clamp_start = start.clamp(DVec2::ZERO, target_size).as_uvec2();
+			let clamp_stop = stop.clamp(DVec2::ZERO, target_size).as_uvec2();
+
+			let blit_area_offset = (clamp_start.as_dvec2() - start).as_uvec2().min(texture_size.as_uvec2());
+			let blit_area_dimensions = (clamp_stop - clamp_start).min(texture_size.as_uvec2() - blit_area_offset);
+
+			// Tight blitting loop. Eagerly assert bounds to hopefully eliminate bounds check inside loop.
+			let texture_index = |x: u32, y: u32| -> usize { (y as usize * texture.width as usize) + (x as usize) };
+			let target_index = |x: u32, y: u32| -> usize { (y as usize * target_width as usize) + (x as usize) };
+
+			let max_y = (blit_area_offset.y + blit_area_dimensions.y).saturating_sub(1);
+			let max_x = (blit_area_offset.x + blit_area_dimensions.x).saturating_sub(1);
+			assert!(texture_index(max_x, max_y) < texture.data.len());
+			assert!(target_index(max_x, max_y) < element.data.len());
+
+			for y in blit_area_offset.y..blit_area_offset.y + blit_area_dimensions.y {
+				for x in blit_area_offset.x..blit_area_offset.x + blit_area_dimensions.x {
+					let src_pixel = texture.data[texture_index(x, y)];
+					let dst_pixel = &mut element.data_mut().data[target_index(x + clamp_start.x, y + clamp_start.y)];
+					*dst_pixel = blend_mode(src_pixel, *dst_pixel);
+				}
+			}
+		}
+	}
+
+	target
+}
+
+pub fn create_brush_texture(brush_style: &BrushStyle) -> Raster<CPU> {
+	let stamp = brush_stamp_generator(&(), brush_style.diameter, brush_style.color, brush_style.hardness, brush_style.flow);
+	let transform = DAffine2::from_scale_angle_translation(DVec2::splat(brush_style.diameter), 0., -DVec2::splat(brush_style.diameter / 2.));
+	let blank_texture = {
+		let mut item = Item::new_from_element(empty_image_core(transform, Color::TRANSPARENT));
+		item.set_attribute(ATTR_TRANSFORM, transform);
+		item
+	};
+	let image = blend_stamp_closure(stamp, blank_texture, |a, b| blend_colors(a, b, BlendMode::Normal, 1.));
+
+	image.into_element()
+}
+
+pub fn blend_with_mode(background: Item<Raster<CPU>>, foreground: Item<Raster<CPU>>, blend_mode: BlendMode, opacity: f64) -> Item<Raster<CPU>> {
+	let opacity = opacity as f32 / 100.;
+	match std::hint::black_box(blend_mode) {
+		// Normal group
+		BlendMode::Normal => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Normal, opacity)),
+		// Darken group
+		BlendMode::Darken => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Darken, opacity)),
+		BlendMode::Multiply => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Multiply, opacity)),
+		BlendMode::ColorBurn => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::ColorBurn, opacity)),
+		BlendMode::LinearBurn => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::LinearBurn, opacity)),
+		BlendMode::DarkerColor => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::DarkerColor, opacity)),
+		// Lighten group
+		BlendMode::Lighten => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Lighten, opacity)),
+		BlendMode::Screen => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Screen, opacity)),
+		BlendMode::ColorDodge => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::ColorDodge, opacity)),
+		BlendMode::LinearDodge => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::LinearDodge, opacity)),
+		BlendMode::LighterColor => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::LighterColor, opacity)),
+		// Contrast group
+		BlendMode::Overlay => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Overlay, opacity)),
+		BlendMode::SoftLight => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::SoftLight, opacity)),
+		BlendMode::HardLight => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::HardLight, opacity)),
+		BlendMode::VividLight => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::VividLight, opacity)),
+		BlendMode::LinearLight => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::LinearLight, opacity)),
+		BlendMode::PinLight => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::PinLight, opacity)),
+		BlendMode::HardMix => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::HardMix, opacity)),
+		// Inversion group
+		BlendMode::Difference => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Difference, opacity)),
+		BlendMode::Exclusion => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Exclusion, opacity)),
+		BlendMode::Subtract => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Subtract, opacity)),
+		BlendMode::Divide => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Divide, opacity)),
+		// Component group
+		BlendMode::Hue => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Hue, opacity)),
+		BlendMode::Saturation => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Saturation, opacity)),
+		BlendMode::Color => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Color, opacity)),
+		BlendMode::Luminosity => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Luminosity, opacity)),
+		// Other utility blend modes (hidden from the normal list)
+		BlendMode::Erase => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Erase, opacity)),
+		BlendMode::Restore => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::Restore, opacity)),
+		BlendMode::MultiplyAlpha => blend_image_closure(foreground, background, |a, b| blend_colors(a, b, BlendMode::MultiplyAlpha, opacity)),
+	}
+}
+
+/// Lane 0 of the materialized background as the legacy item the brush core works
+/// on; an empty level starts from a blank item, as the pre-flip node did.
+fn legacy_background(background: core_types::node::List<'_, Raster<CPU>>) -> Item<Raster<CPU>> {
+	if background.is_empty() {
+		return Item::default();
+	}
+	let lane = background.lane(0);
+	let mut item = Item::new_from_element(background.element_ref(0).clone());
+	item.set_attribute(ATTR_TRANSFORM, lane.attr::<TransformAttr>());
+	item.set_attribute(ATTR_BLEND_MODE, lane.attr::<BlendModeAttr>());
+	item.set_attribute(ATTR_OPACITY, lane.attr::<Opacity>());
+	item.set_attribute(ATTR_OPACITY_FILL, lane.attr::<OpacityFill>());
+	item.set_attribute(ATTR_CLIPPING_MASK, lane.attr::<ClippingMask>());
+	item
+}
+
+/// The brushed image replaces the whole background level with one lane.
+fn brush_extent(_background: ListIn<'_, Raster<CPU>>, _trace: ListIn<'_, BrushStroke>, _level: LevelIn) -> GPoll<Extent> {
+	GPoll::Final(Extent::Exactly(1))
+}
+
+/// Generates the brush strokes painted with the Brush tool as a raster image.
+/// If an input image is supplied, strokes are drawn on top of it, expanding bounds as needed.
+#[node_macro::node(category("Raster"), extent(brush_extent))]
+fn brush<'e>(
+	ctx: impl Ctx + ExtractArena<'e> + ExtractIndex + InjectIndex + Copy,
+	/// Optional raster content that may be drawn onto.
+	background: IList<Raster<CPU>>,
+	/// The list of brush stroke paths drawn by the Brush tool, with each including both its coordinates and styles.
+	trace: IList<BrushStroke>,
+	/// Internal cache data used to accelerate rendering of the brush content.
+	#[data]
+	cache: BrushCache,
+) -> Result<
+	IList<(
+		Raster<CPU>,
+		Attr<'e, TransformAttr>,
+		Attr<'e, BlendModeAttr>,
+		Attr<'e, Opacity>,
+		Attr<'e, OpacityFill>,
+		Attr<'e, ClippingMask>,
+		Attr<'e, EditorLayerPath>,
+	)>,
+	Interrupt,
+> {
+	if ctx.innermost_index() > 0 {
+		return Err(GraphError::past_end().into());
+	}
+	// The layer path only rides through, so it is read off the source lane
+	// rather than round-tripped as a legacy list attribute.
+	let layer_path: Vec<NodeId> = match background.is_empty() {
+		true => Vec::new(),
+		false => background.lane(0).attr::<EditorLayerPath>().to_vec(),
+	};
+	let strokes: Vec<BrushStroke> = (0..trace.len()).map(|row| trace.element_ref(row).clone()).collect();
+	let actual_image = brush_core(legacy_background(background), strokes, cache);
+
+	let transform: DAffine2 = actual_image.attribute_cloned_or_default(ATTR_TRANSFORM);
+	let blend_mode: BlendMode = actual_image.attribute_cloned_or_default(ATTR_BLEND_MODE);
+	let opacity: f64 = actual_image.attribute_cloned_or(ATTR_OPACITY, 1.);
+	let fill: f64 = actual_image.attribute_cloned_or(ATTR_OPACITY_FILL, 1.);
+	let clip: bool = actual_image.attribute_cloned_or_default(ATTR_CLIPPING_MASK);
+	let layer_path = ctx
+		.arena()
+		.alloc(layer_path)
+		.ok_or_else(|| {
+			Interrupt::from(GraphError {
+				kind: core_types::gpoll::ErrorKind::ArenaExhausted,
+				trace: Vec::new(),
+			})
+		})?
+		.0;
+
+	Ok((
+		actual_image.into_element(),
+		Attr(transform),
+		Attr(blend_mode),
+		Attr(opacity),
+		Attr(fill),
+		Attr(clip),
+		Attr(layer_path.as_slice()),
+	))
+}
+
+/// The pre-flip brush body, on legacy items: one background item plus every
+/// stroke in order, returning the painted image.
+fn brush_core(list_item: Item<Raster<CPU>>, strokes: Vec<BrushStroke>, cache: &BrushCache) -> Item<Raster<CPU>> {
+	let bounds = List::new_from_item(list_item.clone()).bounding_box(DAffine2::IDENTITY, false);
+	let [start, end] = if let RenderBoundingBox::Rectangle(rect) = bounds { rect } else { [DVec2::ZERO, DVec2::ZERO] };
+	let background_bbox = AxisAlignedBbox { start, end };
+	let stroke_bbox = strokes.iter().map(|s| s.bounding_box()).reduce(|a, b| a.union(&b)).unwrap_or(AxisAlignedBbox::ZERO);
+	let bbox = if background_bbox.size().length() < 0.1 {
+		stroke_bbox
+	} else {
+		stroke_bbox.union(&background_bbox)
+	};
+	let background_bounds = bbox.to_transform();
+
+	let mut draw_strokes: Vec<_> = strokes.iter().filter(|s| !matches!(s.style.blend_mode, BlendMode::Erase | BlendMode::Restore)).cloned().collect();
+
+	let mut brush_plan = cache.compute_brush_plan(list_item, &draw_strokes);
+
+	// TODO: Find a way to handle more than one item
+	let mut actual_image = {
+		let background = brush_plan.background;
+		let transform: DAffine2 = background.attribute_cloned_or_default(ATTR_TRANSFORM);
+		let (element, attributes) = background.into_parts();
+		let (element, transform) = extend_image_to_bounds_core(element, transform, background_bounds);
+		let mut item = Item::from_parts(element, attributes);
+		item.set_attribute(ATTR_TRANSFORM, transform);
+		item
+	};
+
+	let final_stroke_idx = brush_plan.strokes.len().saturating_sub(1);
+	for (idx, stroke) in brush_plan.strokes.into_iter().enumerate() {
+		// Create brush texture.
+		// TODO: apply rotation from layer to stamp for non-rotationally-symmetric brushes.
+		let mut brush_texture = cache.get_cached_brush(&stroke.style);
+		if brush_texture.is_none() {
+			let tex = create_brush_texture(&stroke.style);
+			cache.store_brush(stroke.style.clone(), tex.clone());
+			brush_texture = Some(tex);
+		}
+		let brush_texture = brush_texture.unwrap();
+
+		// Compute transformation from stroke texture space into layer space, and create the stroke texture.
+		let skip = if idx == 0 { brush_plan.first_stroke_point_skip } else { 0 };
+		let positions: Vec<_> = stroke.compute_blit_points().into_iter().skip(skip).collect();
+		let stroke_texture = if idx == 0 && positions.is_empty() {
+			core::mem::take(&mut brush_plan.first_stroke_texture)
+		} else {
+			let mut bbox = stroke.bounding_box();
+			bbox.start = bbox.start.floor();
+			bbox.end = bbox.end.floor();
+			let stroke_size = bbox.size() + DVec2::splat(stroke.style.diameter);
+			// For numerical stability we want to place the first blit point at a stable, integer offset in layer space.
+			let snap_offset = positions[0].floor() - positions[0];
+			let stroke_origin_in_layer = bbox.start - snap_offset - DVec2::splat(stroke.style.diameter / 2.);
+			let stroke_to_layer = DAffine2::from_translation(stroke_origin_in_layer) * DAffine2::from_scale(stroke_size);
+
+			let blit_target = if idx == 0 {
+				let target = core::mem::take(&mut brush_plan.first_stroke_texture);
+				let transform: DAffine2 = target.attribute_cloned_or_default(ATTR_TRANSFORM);
+				let (element, attributes) = target.into_parts();
+				let (element, transform) = extend_image_to_bounds_core(element, transform, stroke_to_layer);
+				let mut item = Item::from_parts(element, attributes);
+				item.set_attribute(ATTR_TRANSFORM, transform);
+				List::new_from_item(item)
+			} else {
+				let mut item = Item::new_from_element(empty_image_core(stroke_to_layer, Color::TRANSPARENT));
+				item.set_attribute(ATTR_TRANSFORM, stroke_to_layer);
+				List::new_from_item(item)
+			};
+
+			let list = blit(&(), blit_target, brush_texture, positions, |a, b| blend_colors(a, b, BlendMode::Normal, 1.));
+			assert_eq!(list.len(), 1);
+			list.into_iter().next().unwrap_or_default()
+		};
+
+		// Cache image before doing final blend, and store final stroke texture.
+		if idx == final_stroke_idx {
+			cache.cache_results(core::mem::take(&mut draw_strokes), actual_image.clone(), stroke_texture.clone());
+		}
+
+		// TODO: Is this the correct way to do opacity in blending?
+		actual_image = blend_with_mode(actual_image, stroke_texture, stroke.style.blend_mode, (stroke.style.color.a() * 100.) as f64);
+	}
+
+	let has_erase_or_restore_strokes = strokes.iter().any(|s| matches!(s.style.blend_mode, BlendMode::Erase | BlendMode::Restore));
+	if has_erase_or_restore_strokes {
+		let opaque_image = Image::new(bbox.size().x as u32, bbox.size().y as u32, Color::WHITE);
+		let mut erase_restore_mask = Item::new_from_element(Raster::new_cpu(opaque_image)).with_attribute(ATTR_TRANSFORM, background_bounds);
+
+		for stroke in strokes {
+			let mut brush_texture = cache.get_cached_brush(&stroke.style);
+			if brush_texture.is_none() {
+				let tex = create_brush_texture(&stroke.style);
+				cache.store_brush(stroke.style.clone(), tex.clone());
+				brush_texture = Some(tex);
+			}
+			let brush_texture = brush_texture.unwrap();
+			let positions: Vec<_> = stroke.compute_blit_points().into_iter().collect();
+
+			// For mask composition: Erase subtracts alpha, Restore adds alpha, and Draw acts like Restore to allow repainting erased areas.
+			let mask_blend_mode = match stroke.style.blend_mode {
+				BlendMode::Erase => BlendMode::Erase,
+				BlendMode::Restore => BlendMode::Restore,
+				_ => BlendMode::Restore,
+			};
+
+			erase_restore_mask = blit(&(), List::new_from_item(erase_restore_mask), brush_texture, positions, move |a, b| {
+				blend_colors(a, b, mask_blend_mode, 1.)
+			})
+			.into_iter()
+			.next()
+			.unwrap_or_default();
+		}
+
+		actual_image = blend_image_closure(erase_restore_mask, actual_image, |a, b| blend_colors(a, b, BlendMode::MultiplyAlpha, 1.));
+	}
+
+	actual_image
+}
+
+pub fn blend_image_closure(foreground: Item<Raster<CPU>>, mut background: Item<Raster<CPU>>, map_fn: impl Fn(Color, Color) -> Color) -> Item<Raster<CPU>> {
+	let foreground_size = DVec2::new(foreground.element().width as f64, foreground.element().height as f64);
+	let background_size = DVec2::new(background.element().width as f64, background.element().height as f64);
+
+	// Transforms a point from the background image to the foreground image
+	let foreground_transform: DAffine2 = foreground.attribute_cloned_or_default(ATTR_TRANSFORM);
+	let background_transform: DAffine2 = background.attribute_cloned_or_default(ATTR_TRANSFORM);
+	let background_to_foreground = DAffine2::from_scale(foreground_size) * foreground_transform.inverse() * background_transform * DAffine2::from_scale(1. / background_size);
+
+	// Footprint of the foreground image (0, 0)..(1, 1) in the background image space
+	let background_aabb = Bbox::unit().affine_transform(background_transform.inverse() * foreground_transform).to_axis_aligned_bbox();
+
+	// Clamp the foreground image to the background image
+	let start = (background_aabb.start * background_size).max(DVec2::ZERO).as_uvec2();
+	let end = (background_aabb.end * background_size).min(background_size).as_uvec2();
+
+	for y in start.y..end.y {
+		for x in start.x..end.x {
+			let background_point = DVec2::new(x as f64, y as f64);
+			let foreground_point = background_to_foreground.transform_point2(background_point);
+
+			let source_pixel = foreground.element().sample(foreground_point);
+			let Some(destination_pixel) = background.element_mut().data_mut().get_pixel_mut(x, y) else {
+				continue;
+			};
+
+			*destination_pixel = map_fn(source_pixel, *destination_pixel);
+		}
+	}
+
+	background
+}
+
+pub fn blend_stamp_closure(foreground: BrushStampGenerator<Color>, mut background: Item<Raster<CPU>>, map_fn: impl Fn(Color, Color) -> Color) -> Item<Raster<CPU>> {
+	let background_size = DVec2::new(background.element().width as f64, background.element().height as f64);
+
+	// Transforms a point from the background image to the foreground image
+	let background_transform: DAffine2 = background.attribute_cloned_or_default(ATTR_TRANSFORM);
+	let background_to_foreground = background_transform * DAffine2::from_scale(1. / background_size);
+
+	// Footprint of the foreground image (0, 0)..(1, 1) in the background image space
+	let background_aabb = Bbox::unit().affine_transform(background_transform.inverse() * foreground.transform()).to_axis_aligned_bbox();
+
+	// Clamp the foreground image to the background image
+	let start = (background_aabb.start * background_size).max(DVec2::ZERO).as_uvec2();
+	let end = (background_aabb.end * background_size).min(background_size).as_uvec2();
+
+	let area = background_to_foreground.transform_point2(DVec2::new(1., 1.)) - background_to_foreground.transform_point2(DVec2::ZERO);
+	for y in start.y..end.y {
+		for x in start.x..end.x {
+			let background_point = DVec2::new(x as f64, y as f64);
+			let foreground_point = background_to_foreground.transform_point2(background_point);
+
+			let Some(source_pixel) = foreground.sample(foreground_point, area) else { continue };
+			let Some(destination_pixel) = background.element_mut().data_mut().get_pixel_mut(x, y) else {
+				continue;
+			};
+
+			*destination_pixel = map_fn(source_pixel, *destination_pixel);
+		}
+	}
+
+	background
+}
+
+#[cfg(test)]
+mod test {
+	use super::*;
+	use crate::brush_stroke::BrushStroke;
+	use core_types::transform::Transform;
+	use glam::DAffine2;
+
+	#[test]
+	fn test_brush_texture() {
+		let size = 20.;
+		let image = brush_stamp_generator(&(), size, Color::BLACK, 100., 100.);
+		assert_eq!(image.transform(), DAffine2::from_scale_angle_translation(DVec2::splat(size.ceil()), 0., -DVec2::splat(size / 2.)));
+		// center pixel should be BLACK
+		assert_eq!(image.sample(DVec2::splat(0.), DVec2::ONE), Some(Color::BLACK));
+	}
+
+	#[test]
+	fn test_brush_output_size() {
+		let image = brush_core(
+			Item::new_from_element(Raster::new_cpu(Image::<Color>::default())),
+			vec![BrushStroke {
+				trace: vec![crate::brush_stroke::BrushInputSample { position: DVec2::ZERO }],
+				style: BrushStyle {
+					color: Color::BLACK,
+					diameter: 20.,
+					hardness: 20.,
+					flow: 20.,
+					spacing: 20.,
+					blend_mode: BlendMode::Normal,
+				},
+			}],
+			&BrushCache::default(),
+		);
+		assert_eq!(image.element().width, 20);
+	}
+}
@@ -0,0 +1,116 @@
+use crate::brush_stroke::BrushStroke;
+use crate::brush_stroke::BrushStyle;
+use core_types::ATTR_TRANSFORM;
+use core_types::graphene_hash::CacheHashWrapper;
+use core_types::list::Item;
+use raster_types::CPU;
+use raster_types::Raster;
+use std::collections::HashMap;
+use std::sync::{Arc, Mutex};
+
+#[derive(Clone, Debug, Default)]
+struct BrushCacheImpl {
+	// The full previous input that was cached.
+	prev_input: Vec<BrushStroke>,
+
+	// The strokes that have been fully processed and blended into the background.
+	background: Item<Raster<CPU>>,
+	blended_image: Item<Raster<CPU>>,
+	last_stroke_texture: Item<Raster<CPU>>,
+
+	// A cache for brush textures.
+	brush_texture_cache: HashMap<CacheHashWrapper<BrushStyle>, Raster<CPU>>,
+}
+
+impl BrushCacheImpl {
+	fn compute_brush_plan(&mut self, mut background: Item<Raster<CPU>>, input: &[BrushStroke]) -> BrushPlan {
+		// Do background invalidation.
+		if background != self.background {
+			self.background = background.clone();
+			return BrushPlan {
+				strokes: input.to_vec(),
+				background,
+				..Default::default()
+			};
+		}
+
+		// Do blended_image invalidation.
+		let blended_strokes = &self.prev_input[..self.prev_input.len().saturating_sub(1)];
+		let num_blended_strokes = blended_strokes.len();
+		if input.get(..num_blended_strokes) != Some(blended_strokes) {
+			return BrushPlan {
+				strokes: input.to_vec(),
+				background,
+				..Default::default()
+			};
+		}
+
+		// Take our previous blended image (and invalidate the cache).
+		// Since we're about to replace our cache anyway, this saves a clone.
+		background = std::mem::take(&mut self.blended_image);
+
+		// Check if the first non-blended stroke is an extension of the last one.
+		// Transform is set to ZERO (not the default IDENTITY) as a sentinel to mark this item as uninitialized.
+		let mut first_stroke_texture = Item::new_from_element(Raster::<CPU>::default()).with_attribute(ATTR_TRANSFORM, glam::DAffine2::ZERO);
+		let mut first_stroke_point_skip = 0;
+		let strokes = input[num_blended_strokes..].to_vec();
+		if !strokes.is_empty() && self.prev_input.len() > num_blended_strokes {
+			let last_stroke = &self.prev_input[num_blended_strokes];
+			let same_style = strokes[0].style == last_stroke.style;
+			let prev_points = last_stroke.compute_blit_points();
+			let new_points = strokes[0].compute_blit_points();
+			let is_point_prefix = new_points.get(..prev_points.len()) == Some(&prev_points);
+			if same_style && is_point_prefix {
+				first_stroke_texture = std::mem::take(&mut self.last_stroke_texture);
+				first_stroke_point_skip = prev_points.len();
+			}
+		}
+
+		self.prev_input = Vec::new();
+		BrushPlan {
+			strokes,
+			background,
+			first_stroke_texture,
+			first_stroke_point_skip,
+		}
+	}
+
+	pub fn cache_results(&mut self, input: Vec<BrushStroke>, blended_image: Item<Raster<CPU>>, last_stroke_texture: Item<Raster<CPU>>) {
+		self.prev_input = input;
+		self.blended_image = blended_image;
+		self.last_stroke_texture = last_stroke_texture;
+	}
+}
+
+#[derive(Clone, Debug, Default)]
+pub struct BrushPlan {
+	pub strokes: Vec<BrushStroke>,
+	pub background: Item<Raster<CPU>>,
+	pub first_stroke_texture: Item<Raster<CPU>>,
+	pub first_stroke_point_skip: usize,
+}
+
+#[derive(Debug, Default, Clone)]
+pub struct BrushCache(Arc<Mutex<BrushCacheImpl>>);
+
+impl BrushCache {
+	pub fn compute_brush_plan(&self, background: Item<Raster<CPU>>, input: &[BrushStroke]) -> BrushPlan {
+		let mut inner = self.0.lock().unwrap();
+		inner.compute_brush_plan(background, input)
+	}
+
+	pub fn cache_results(&self, input: Vec<BrushStroke>, blended_image: Item<Raster<CPU>>, last_stroke_texture: Item<Raster<CPU>>) {
+		let mut inner = self.0.lock().unwrap();
+		inner.cache_results(input, blended_image, last_stroke_texture)
+	}
+
+	pub fn get_cached_brush(&self, style: &BrushStyle) -> Option<Raster<CPU>> {
+		let inner = self.0.lock().unwrap();
+		inner.brush_texture_cache.get(&CacheHashWrapper(style.clone())).cloned()
+	}
+
+	pub fn store_brush(&self, style: BrushStyle, brush: Raster<CPU>) {
+		let mut inner = self.0.lock().unwrap();
+		inner.brush_texture_cache.insert(CacheHashWrapper(style), brush);
+	}
+}
@@ -0,0 +1,125 @@
+use core_types::CacheHash;
+use core_types::blending::BlendMode;
+use core_types::color::Color;
+use core_types::list::{Item, List};
+use core_types::math::bbox::AxisAlignedBbox;
+use dyn_any::DynAny;
+use glam::DVec2;
+/// The style of a brush.
+#[derive(Clone, Debug, CacheHash, DynAny)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct BrushStyle {
+	pub color: Color,
+	pub diameter: f64,
+	pub hardness: f64,
+	pub flow: f64,
+	pub spacing: f64, // Spacing as a fraction of the diameter.
+	pub blend_mode: BlendMode,
+}
+
+impl Default for BrushStyle {
+	fn default() -> Self {
+		Self {
+			color: Color::BLACK,
+			diameter: 40.,
+			hardness: 50.,
+			flow: 100.,
+			spacing: 50., // Percentage of diameter.
+			blend_mode: BlendMode::Normal,
+		}
+	}
+}
+
+impl Eq for BrushStyle {}
+
+impl PartialEq for BrushStyle {
+	fn eq(&self, other: &Self) -> bool {
+		self.color == other.color
+			&& self.diameter.to_bits() == other.diameter.to_bits()
+			&& self.hardness.to_bits() == other.hardness.to_bits()
+			&& self.flow.to_bits() == other.flow.to_bits()
+			&& self.spacing.to_bits() == other.spacing.to_bits()
+			&& self.blend_mode == other.blend_mode
+	}
+}
+
+/// A single sample of brush parameters across the brush stroke.
+#[derive(Clone, Debug, PartialEq, core_types::CacheHash, DynAny)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct BrushInputSample {
+	pub position: DVec2,
+}
+
+/// The parameters for a single stroke brush.
+#[derive(Clone, Debug, PartialEq, core_types::CacheHash, Default, DynAny)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct BrushStroke {
+	pub style: BrushStyle,
+	pub trace: Vec<BrushInputSample>,
+}
+
+/// One Brush layer's full sequence of strokes, treated as a single rank-0 value rather than a frame of independent strokes.
+#[derive(Default, Debug, Clone, PartialEq, CacheHash, DynAny)]
+pub struct BrushTrace(pub List<BrushStroke>);
+
+impl From<List<BrushStroke>> for BrushTrace {
+	fn from(strokes: List<BrushStroke>) -> Self {
+		Self(strokes)
+	}
+}
+
+impl From<Vec<BrushStroke>> for BrushTrace {
+	fn from(strokes: Vec<BrushStroke>) -> Self {
+		Self(strokes.into_iter().map(Item::new_from_element).collect())
+	}
+}
+
+impl BrushStroke {
+	pub fn bounding_box(&self) -> AxisAlignedBbox {
+		let radius = self.style.diameter / 2.;
+		self.compute_blit_points()
+			.iter()
+			.map(|pos| AxisAlignedBbox {
+				start: *pos + DVec2::new(-radius, -radius),
+				end: *pos + DVec2::new(radius, radius),
+			})
+			.reduce(|a, b| a.union(&b))
+			.unwrap_or(AxisAlignedBbox::ZERO)
+	}
+
+	pub fn compute_blit_points(&self) -> Vec<DVec2> {
+		// We always travel in a straight line towards the next user input,
+		// placing a blit point every time we travelled our spacing distance.
+		let spacing_dist = self.style.spacing / 100. * self.style.diameter;
+
+		let Some(first_sample) = self.trace.first() else {
+			return Vec::new();
+		};
+
+		let mut cur_pos = first_sample.position;
+		let mut result = vec![cur_pos];
+		let mut dist_until_next_blit = spacing_dist;
+		for sample in &self.trace[1..] {
+			// Travel to the next sample.
+			let delta = sample.position - cur_pos;
+			let mut dist_left = delta.length();
+			let unit_step = delta / dist_left;
+
+			while dist_left >= dist_until_next_blit {
+				// Take a step to the next blit point.
+				cur_pos += dist_until_next_blit * unit_step;
+				dist_left -= dist_until_next_blit;
+
+				// Blit.
+				result.push(cur_pos);
+				dist_until_next_blit = spacing_dist;
+			}
+
+			// Take the partial step to land at the sample.
+			dist_until_next_blit -= dist_left;
+			cur_pos = sample.position;
+		}
+
+		result
+	}
+}
@@ -0,0 +1,30 @@
+pub mod brush;
+mod brush_cache;
+pub mod brush_stroke;
+
+pub mod migrations {
+	use crate::brush_stroke::BrushStroke;
+
+	// TODO: Eventually remove this migration document upgrade code
+	pub fn migrate_to_brush_strokes<'de, D: serde::Deserializer<'de>>(deserializer: D) -> Result<Vec<BrushStroke>, D::Error> {
+		use serde::Deserialize;
+
+		#[derive(serde::Deserialize)]
+		struct LegacyTable {
+			#[serde(alias = "instances", alias = "instance")]
+			element: Vec<BrushStroke>,
+		}
+
+		#[derive(serde::Deserialize)]
+		#[serde(untagged)]
+		enum BrushStrokesFormat {
+			Strokes(Vec<BrushStroke>),
+			List(LegacyTable),
+		}
+
+		Ok(match BrushStrokesFormat::deserialize(deserializer)? {
+			BrushStrokesFormat::Strokes(strokes) => strokes,
+			BrushStrokesFormat::List(list) => list.element,
+		})
+	}
+}