donner::geode::EncodedPath Struct Reference

GPU-ready encoded path data produced by the Slug band decomposition algorithm. More...

#include "donner/svg/renderer/geode/GeodePathEncoder.h"

Collaboration diagram for donner::geode::EncodedPath:

Classes
struct	Curve
	A quadratic Bézier curve segment (3 control points) stored as floats for GPU consumption. More...
struct	Band
	Metadata for one horizontal band. More...
struct	Vertex
	Vertex for the band bounding quad (input to the Slug vertex shader). More...

Public Member Functions
bool	empty () const
	Returns true if the encoded path has no bands (empty or degenerate path).

Public Attributes
std::vector< Curve >	curves
	Horizontal (Y-monotonic) curves, sorted by band.
std::vector< Band >	bands
	Horizontal band metadata (Y-strips), for the horizontal ray.
std::vector< Vertex >	vertices
	Per-band bounding quad vertices (6 per band) — legacy 4-sample path (gradient/mask alpha-coverage shaders).
Box2d	pathBounds
	Axis-aligned bounding box of the path.
std::vector< Vertex >	quadVertices
	Single bounding quad (6 verts) over the whole path, for the analytic dual-ray fill shader (0041 §8.1). One quad per path means each pixel is rasterized by exactly one fragment, so folded sampleCount=1 coverage composes correctly (no band-seam double-count — Blocker B). bandIndex is unused (the fragment looks up both its H- and V-band from sample_pos via the band grids).
std::vector< Curve >	vCurves
	Vertical (X-monotonic) curve + band data, for the Slug vertical ray used by the dual-ray analytic coverage (see docs/design_docs/0041). These mirror curves/bands but are split at X-extrema and binned into vertical (X-strip) bands. For a vertical Band the field semantics are transposed: xMin/xMax are the band's X-strip boundaries and yMin/yMax are the Y-extent of the curves in the band.
std::vector< Band >	vBands
	Vertical band metadata (X-strips), for the vertical ray.
std::vector< uint32_t >	hBandGrid
	Dense band-grid lookup, for the analytic dual-ray fragment shader (0041 §8.1). The shader finds its band in O(1) from the sample position: slot = hBandGrid[clamp(floor((y - yBase) / hStride), 0, hBandCount-1)] if (slot != kNoBand) iterate bands[slot]'s curves for the horizontal ray. vBandGrid indexes vBands by (x - xBase) / vStride for the vertical ray. The grids map dense grid cells onto the empty-skipped bands/vBands arrays, so no curve data is duplicated. Empty for a degenerate axis (count 0).
std::vector< uint32_t >	vBandGrid
	size == vBandCount; cell → index into vBands.
float	yBase = 0.0f
	Top edge of the horizontal band grid (path space).
float	hStride = 0.0f
	Height of each horizontal band cell (path space).
uint32_t	hBandCount = 0
	Number of horizontal band cells.
float	xBase = 0.0f
	Left edge of the vertical band grid (path space).
float	vStride = 0.0f
	Width of each vertical band cell (path space).
uint32_t	vBandCount = 0
	Number of vertical band cells.

Static Public Attributes
static constexpr uint32_t	kNoBand = 0xFFFFFFFFu
	Sentinel for a grid cell with no band (no curves overlap that strip).

Detailed Description

GPU-ready encoded path data produced by the Slug band decomposition algorithm.

This struct contains all the data needed by the Slug vertex and fragment shaders to render a filled path. It is produced by GeodePathEncoder::encode() and consumed by the GPU pipeline.

The data is organized as:

• Curves: Quadratic Bézier control points (3 × Vector2f per curve), packed contiguously.
• Bands: Horizontal slices through the path. Each band references a contiguous range of curves and has a bounding quad for rasterization.
• Vertices: The bounding quads for each band (6 vertices per band = 2 triangles), with position, outward normal, and band index attributes for the vertex shader.

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Class Documentation

donner::geode::EncodedPath::Curve

struct donner::geode::EncodedPath::Curve

A quadratic Bézier curve segment (3 control points) stored as floats for GPU consumption.

Class Members
float	p0x
float	p0y	Start point.
float	p1x
float	p1y	Control point.
float	p2x
float	p2y	End point.

donner::geode::EncodedPath::Band

struct donner::geode::EncodedPath::Band

Metadata for one horizontal band.

Layout matches the WGSL Band struct in shaders/slug_fill.wgsl exactly (8 × 4 bytes = 32 bytes per band). Two trailing pad fields are required because storage buffer struct stride must be 16-byte aligned, and without them WGSL would round the struct to 32 bytes anyway.

Class Members
float	_pad0	Padding to match WGSL stride.
float	_pad1	Padding to match WGSL stride.
uint32_t	curveCount	Number of curves intersecting this band.
uint32_t	curveStart	Index of the first curve in this band's curve range.
float	xMax	Right extent of curves in this band.
float	xMin	Left extent of curves in this band.
float	yMax	Top edge of the band (in path space).
float	yMin	Bottom edge of the band (in path space).

donner::geode::EncodedPath::Vertex

struct donner::geode::EncodedPath::Vertex

Vertex for the band bounding quad (input to the Slug vertex shader).

Class Members
uint32_t	bandIndex	Which band this vertex belongs to.
float	normalX
float	normalY	Outward normal (for dynamic half-pixel dilation).
float	posX
float	posY	Position in path space.

Member Data Documentation

hBandGrid

std::vector<uint32_t> donner::geode::EncodedPath::hBandGrid

Dense band-grid lookup, for the analytic dual-ray fragment shader (0041 §8.1). The shader finds its band in O(1) from the sample position: slot = hBandGrid[clamp(floor((y - yBase) / hStride), 0, hBandCount-1)] if (slot != kNoBand) iterate bands[slot]'s curves for the horizontal ray. vBandGrid indexes vBands by (x - xBase) / vStride for the vertical ray. The grids map dense grid cells onto the empty-skipped bands/vBands arrays, so no curve data is duplicated. Empty for a degenerate axis (count 0).

size == hBandCount; cell → index into bands.

vCurves

std::vector<Curve> donner::geode::EncodedPath::vCurves

Vertical (X-monotonic) curve + band data, for the Slug vertical ray used by the dual-ray analytic coverage (see docs/design_docs/0041). These mirror curves/bands but are split at X-extrema and binned into vertical (X-strip) bands. For a vertical Band the field semantics are transposed: xMin/xMax are the band's X-strip boundaries and yMin/yMax are the Y-extent of the curves in the band.

X-monotonic curves, sorted by vertical band.

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The documentation for this struct was generated from the following file:

• donner/svg/renderer/geode/GeodePathEncoder.h