forked from 1b-agent/opencadstudio-upstream
192 lines
6.9 KiB
WebGPU Shading Language
192 lines
6.9 KiB
WebGPU Shading Language
// Hatch shader — GPU-driven hatch fill over an arbitrary polygon boundary.
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//
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// Vertex shader : projects a bounding-box quad over the hatch region.
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// Fragment shader: three stages —
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// 1. Point-in-polygon (ray casting against boundary vertices in world XY).
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// 2. Pattern test:
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// mode 0 — N line families (PAT format), each with optional dash pattern.
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// mode 1 — solid fill.
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// mode 2 — linear gradient.
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//
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// GPU limits: MAX_FAMILIES = 16, MAX_DASHES = 128.
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// ── Group 0: frame uniforms (shared) ──────────────────────────────────────
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struct Uniforms {
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view_proj: mat4x4<f32>,
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camera_pos: vec4<f32>,
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viewport_size: vec2<f32>,
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_pad: vec2<f32>,
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}
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@group(0) @binding(0) var<uniform> u: Uniforms;
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// ── Group 1: per-hatch data ────────────────────────────────────────────────
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//
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// mode encoding:
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// 0 → Pattern (evaluate FamilyBatch)
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// 1 → Solid (return h.color immediately)
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// 2 → Gradient (mix h.color → h.color2 along grad_cos/grad_sin)
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struct HatchUniforms {
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color: vec4<f32>, // 0: primary RGBA
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color2: vec4<f32>, // 16: gradient end color
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mode: u32, // 32: 0=pattern, 1=solid, 2=gradient
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vcount: u32, // 36: boundary vertex count
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angle_offset: f32, // 40: pattern rotation (radians, added to each family)
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scale: f32, // 44: pattern scale multiplier
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grad_cos: f32, // 48: gradient direction cos
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grad_sin: f32, // 52: gradient direction sin
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grad_min: f32, // 56: gradient proj_min
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grad_range: f32, // 60: gradient proj_range
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}
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@group(1) @binding(0) var<uniform> h: HatchUniforms;
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struct Boundary {
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verts: array<vec4<f32>, 64>,
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}
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@group(1) @binding(1) var<uniform> b: Boundary;
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// One line family (48 bytes, matches LineFamilyGpu in hatch_gpu.rs).
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struct LineFamily {
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cos_a: f32, // base cos(angle)
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sin_a: f32, // base sin(angle)
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x0: f32, // family origin x
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y0: f32, // family origin y
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dx: f32, // step vector x
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dy: f32, // step vector y
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perp_step: f32, // -dx*sin_a + dy*cos_a (perpendicular spacing)
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along_step: f32, // dx*cos_a + dy*sin_a (phase shift per step)
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line_width: f32, // half-width of each line (|perp_step| × 0.08)
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period: f32, // sum(|dashes|) — 0 means solid
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n_dashes: u32, // number of dash entries
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dash_off: u32, // start index in dash_values
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}
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struct FamilyBatch {
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families: array<LineFamily, 16>,
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dash_values: array<vec4<f32>, 32>, // 128 f32s packed as 32×vec4 (uniform stride=16)
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n_families: u32,
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_pad0: u32, _pad1: u32, _pad2: u32,
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}
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@group(1) @binding(2) var<uniform> f: FamilyBatch;
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// ── Vertex shader ──────────────────────────────────────────────────────────
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struct VIn { @location(0) pos: vec3<f32> }
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struct VOut {
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@builtin(position) clip: vec4<f32>,
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@location(0) xz: vec2<f32>,
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}
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@vertex fn vs_main(v: VIn) -> VOut {
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var o: VOut;
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o.clip = u.view_proj * vec4<f32>(v.pos, 1.0);
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o.xz = vec2<f32>(v.pos.x, v.pos.y);
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return o;
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}
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// ── Point-in-polygon (ray casting) ────────────────────────────────────────
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fn in_polygon(p: vec2<f32>) -> bool {
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var inside = false;
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let n = h.vcount;
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var j = n - 1u;
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for (var i = 0u; i < n; i++) {
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let vi = b.verts[i].xy;
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let vj = b.verts[j].xy;
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if (vi.y > p.y) != (vj.y > p.y) {
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let x_int = (vj.x - vi.x) * (p.y - vi.y) / (vj.y - vi.y) + vi.x;
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if p.x < x_int { inside = !inside; }
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}
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j = i;
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}
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return inside;
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}
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// ── Per-family hatch test ─────────────────────────────────────────────────
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//
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// Returns true if world point `xz` falls on a hatch line of `fam`.
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// `cos_off` / `sin_off` are cos/sin of `h.angle_offset` (precomputed once).
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// `scale` is `h.scale`.
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fn check_family(
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xz: vec2<f32>,
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fam: LineFamily,
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cos_off: f32,
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sin_off: f32,
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scale: f32,
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) -> bool {
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// Rotate family direction by angle_offset.
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let cos_a = fam.cos_a * cos_off - fam.sin_a * sin_off;
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let sin_a = fam.sin_a * cos_off + fam.cos_a * sin_off;
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// Rotate and scale the family origin.
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let ox = (fam.x0 * cos_off - fam.y0 * sin_off) * scale;
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let oz = (fam.x0 * sin_off + fam.y0 * cos_off) * scale;
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let px = xz.x - ox;
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let pz = xz.y - oz;
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// Perpendicular distance from the nearest parallel line.
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let perp_step = fam.perp_step * scale;
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let line_w = abs(fam.line_width * scale);
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let perp = -px * sin_a + pz * cos_a;
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let k = round(perp / perp_step);
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let d = abs(perp - k * perp_step);
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let half_px = length(vec2<f32>(dpdx(perp), dpdy(perp))) * 0.5;
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if d > half_px { return false; }
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// Solid line family — no dash check needed.
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if fam.n_dashes == 0u { return true; }
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// Dash pattern test: position along line k.
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let along_step = fam.along_step * scale;
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let period = fam.period * scale;
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let along = px * cos_a + pz * sin_a;
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let t = along - k * along_step;
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let t_mod = ((t % period) + period) % period;
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var pos = 0.0;
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for (var j = 0u; j < fam.n_dashes; j++) {
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let idx = fam.dash_off + j;
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let sv = f.dash_values[idx / 4u][idx % 4u] * scale; // scale dash lengths
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if sv > 0.0 {
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if t_mod >= pos && t_mod < pos + sv { return true; }
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pos = pos + sv;
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} else {
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pos = pos - sv;
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}
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}
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return false;
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}
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// ── Fragment shader ────────────────────────────────────────────────────────
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@fragment fn fs_main(v: VOut) -> @location(0) vec4<f32> {
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// 1. Boundary test.
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if !in_polygon(v.xz) { discard; }
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// 2. Mode dispatch.
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if h.mode == 1u {
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// Solid fill.
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return h.color;
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} else if h.mode == 2u {
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// Linear gradient.
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let proj = v.xz.x * h.grad_cos + v.xz.y * h.grad_sin;
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let t = clamp((proj - h.grad_min) / h.grad_range, 0.0, 1.0);
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return mix(h.color, h.color2, t);
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}
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// 3. Pattern: evaluate each line family.
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let cos_off = cos(h.angle_offset);
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let sin_off = sin(h.angle_offset);
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for (var i = 0u; i < f.n_families; i++) {
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if check_family(v.xz, f.families[i], cos_off, sin_off, h.scale) {
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return h.color;
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}
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}
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discard;
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}
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