forked from 1b-agent/opencadstudio-upstream
Hakan SevenandClaude Fable 5
84adb71cee
Wire segments expanded only perpendicular to their axis, leaving wedge gaps on the outside of corners and along tessellated arcs once a band is wider than a pixel. Extend each quad longitudinally by the end half-width and round the overhang off in the fragment stage: adjoining segments now meet in overlapping round joints and line ends get round caps, with the dash arc-length extrapolated across the overhang so patterns stay continuous through a joint. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
302 lines
13 KiB
WebGPU Shading Language
302 lines
13 KiB
WebGPU Shading Language
// Wire shader — renders 1-D CAD entities as screen-aligned quads.
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// Topology: TriangleList, 6 vertices drawn per INSTANCE.
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//
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// One instance = one segment. The six vertex IDs map to the corners of a
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// two-triangle quad; the vertex shader derives `which_end` (0=A end, 1=B end)
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// and `side` (±1 perpendicular) from `@builtin(vertex_index)` and expands the
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// quad by `half_width` pixels perpendicular to the segment direction in
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// screen space.
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//
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// Linetype is applied entirely on the GPU:
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// • distance = cumulative arc-length, linearly interpolated from
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// (distance_a, distance_b) by `which_end`.
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// • pattern_length > 0 enables the dash test; 0 = solid (no discard).
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// • pat0/pat1 encode up to 8 elements: positive=dash, negative=gap,
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// exactly 0=dot (rendered as a fixed ~1 px mark). Trailing 0.0 slots are
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// padding; the real element count is (index of last non-zero) + 1.
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struct Uniforms {
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viewport_size: vec2<f32>,
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world_per_pixel: f32,
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// LWDISPLAY toggle: 0.0 = force 1 px (half_width 0.5), 1.0 = use the
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// per-instance baked half_width. Lets the LWT button switch without
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// retessellating.
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lwdisplay_enable: f32,
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// Mesh flat-shade flag (unused here; kept so the field offsets match
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// the shared Uniforms buffer layout).
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flat_shade: f32,
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// Transparency-display toggle: 1.0 = honour baked alpha, 0.0 = force
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// every line opaque.
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transparency_enable: f32,
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_pad: vec2<f32>,
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// ── Relative-to-eye (double-single) ──────────────────────────────────
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// view_rot is the rotation-only view-projection; vertices subtract the eye
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// (eye_high + eye_low, two f32 emulating f64) before transforming, so the
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// large eye translation never enters the f32 matrix → no large-coordinate
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// jitter on pan / zoom / rotate.
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view_rot: mat4x4<f32>,
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eye_high: vec3<f32>,
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_pad_eh: f32,
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eye_low: vec3<f32>,
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_pad_el: f32,
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}
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@group(0) @binding(0) var<uniform> u: Uniforms;
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struct InstanceIn {
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@location(0) pos_a: vec3<f32>,
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@location(1) pos_b: vec3<f32>,
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@location(2) color: vec4<f32>,
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@location(3) distance_a: f32,
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@location(4) distance_b: f32,
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@location(5) half_width: f32,
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@location(6) pattern_length: f32,
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@location(7) pat0: vec4<f32>,
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@location(8) pat1: vec4<f32>,
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@location(9) draw_depth: f32,
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// Double-single low residuals of the endpoints.
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@location(10) pos_a_low: vec3<f32>,
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@location(11) pos_b_low: vec3<f32>,
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// "A"-type endpoint alignment: end-dash length + total wire length.
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@location(12) align_end: f32,
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@location(13) align_total: f32,
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// World-space half-width for a wide-polyline band. 0 = normal wire.
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@location(14) world_half_width: f32,
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// Per-endpoint world half-width for a tapered band (0 = use the constant).
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@location(15) world_hw_a: f32,
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@location(16) world_hw_b: f32,
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}
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// Draw-order depth bias: shifts clip-space z so 2D entities of different
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// types order against each other through the shared LessEqual depth test.
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// draw_depth is signed (-1,1): front → positive → smaller z → drawn on top;
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// 0.0 = neutral (real depth). Depth32Float gives ample precision.
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const DRAW_ORDER_BIAS: f32 = 0.001;
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struct VertexOut {
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@builtin(position) clip_pos: vec4<f32>,
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@location(0) color: vec4<f32>,
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@location(1) distance: f32,
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@location(2) pattern_length: f32,
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@location(3) pat0: vec4<f32>,
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@location(4) pat1: vec4<f32>,
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// World length of the smallest non-zero dash / gap element of this
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// instance. Flat-interpolated (constant per instance) so the
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// fragment stage can short-circuit the dash test when every gap
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// projects below one pixel on screen. See the LOD branch in
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// `fs_main`.
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@location(5) @interpolate(flat) min_elem: f32,
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@location(6) @interpolate(flat) align_end: f32,
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@location(7) @interpolate(flat) align_total: f32,
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// Round-cap support: (along, across) of this fragment in screen pixels,
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// where `along` runs -hw_a … seg_len+hw_b over the extended quad and
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// `across` is the signed distance from the centreline.
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@location(8) cap: vec2<f32>,
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// (segment pixel length, end half-width at A, end half-width at B).
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@location(9) @interpolate(flat) cap_ends: vec3<f32>,
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}
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// Half-width of one segment end: a tapered band's own end width wins, then a
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// constant world-unit band, then the screen-pixel lineweight (LWDISPLAY off
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// collapses to a hairline).
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fn resolve_hw(taper: f32, world_hw: f32, px_hw: f32) -> f32 {
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if taper > 0.0 { return max(taper / u.world_per_pixel, 0.5); }
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if world_hw > 0.0 { return max(world_hw / u.world_per_pixel, 0.5); }
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return select(0.5, px_hw, u.lwdisplay_enable > 0.5);
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}
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@vertex fn vs_main(@builtin(vertex_index) vid: u32, in: InstanceIn) -> VertexOut {
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// Two-triangle quad corner table:
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// vid 0,1,2 = (A,-1) (B,-1) (B,+1)
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// vid 3,4,5 = (A,-1) (B,+1) (A,+1)
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let which_end_arr = array<f32, 6>(0.0, 1.0, 1.0, 0.0, 1.0, 0.0);
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let side_arr = array<f32, 6>(-1.0, -1.0, 1.0, -1.0, 1.0, 1.0);
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let which_end = which_end_arr[vid];
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let side = side_arr[vid];
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// Double-single relative-to-eye: subtract the eye from each endpoint with
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// both halves of the f64-emulating pair, then transform by the rotation-only
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// view-projection. (pos_high − eye_high) is exact in f32 for same-magnitude
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// operands (Sterbenz); adding (pos_low − eye_low) restores the residual both
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// the vertex and the eye would otherwise lose — so geometry stays put at
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// UTM-scale coordinates and after a cross-drawing paste, with no jitter.
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let rel_a = (in.pos_a - u.eye_high) + (in.pos_a_low - u.eye_low);
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let rel_b = (in.pos_b - u.eye_high) + (in.pos_b_low - u.eye_low);
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let clip_a = u.view_rot * vec4<f32>(rel_a, 1.0);
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let clip_b = u.view_rot * vec4<f32>(rel_b, 1.0);
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// NDC of both endpoints.
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let ndc_a = clip_a.xy / clip_a.w;
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let ndc_b = clip_b.xy / clip_b.w;
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// Screen-space pixel positions.
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let screen_a = ndc_a * u.viewport_size * 0.5;
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let screen_b = ndc_b * u.viewport_size * 0.5;
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// Screen-space direction / perpendicular of the segment.
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let seg = screen_b - screen_a;
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let seg_len = length(seg);
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var dir: vec2<f32>;
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if seg_len > 1e-4 {
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dir = seg / seg_len;
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} else {
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dir = vec2<f32>(1.0, 0.0);
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}
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let perp = vec2<f32>(-dir.y, dir.x);
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// Select the clip-space position for this vertex's endpoint.
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let clip_pos = mix(clip_a, clip_b, which_end);
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// A wide polyline carries its band width in world units: expand the quad by
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// `world_half_width / world_per_pixel` (pixels) so the band tracks zoom. A
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// normal wire (world_half_width == 0) uses the screen-pixel half-width,
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// honouring the LWDISPLAY toggle (off → collapse to a 1-pixel line).
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// A tapered band interpolates a per-endpoint world half-width across the
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// segment; a constant band uses `world_half_width`. Both clamp to a
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// half-pixel so a zoomed-out band stays a hairline instead of vanishing.
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let hw_a = resolve_hw(in.world_hw_a, in.world_half_width, in.half_width);
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let hw_b = resolve_hw(in.world_hw_b, in.world_half_width, in.half_width);
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let hw = mix(hw_a, hw_b, which_end);
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// Extend the quad longitudinally by the end half-width and let the
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// fragment stage round the overhang off: adjoining segments then meet in
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// overlapping round joints, closing the wedge gaps a perpendicular-only
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// expansion leaves on the outside of corners and along tessellated arcs.
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let ext = which_end * 2.0 - 1.0; // -1 at the A end, +1 at the B end
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let offset_px = perp * hw * side + dir * hw * ext;
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let ndc_offset = offset_px / (u.viewport_size * 0.5);
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let final_clip = clip_pos + vec4<f32>(ndc_offset * clip_pos.w, 0.0, 0.0);
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// Smallest non-zero dash / gap element, in world units. Used by
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// the fragment stage to decide when the pattern's finest feature
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// would render below one pixel and should collapse to a solid line.
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var min_elem: f32 = in.pattern_length;
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let elems = array<f32, 8>(
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in.pat0.x, in.pat0.y, in.pat0.z, in.pat0.w,
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in.pat1.x, in.pat1.y, in.pat1.z, in.pat1.w,
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);
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for (var i = 0u; i < 8u; i++) {
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let e = abs(elems[i]);
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if e > 0.0 && e < min_elem { min_elem = e; }
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}
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var out: VertexOut;
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out.clip_pos = final_clip;
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out.clip_pos.z = out.clip_pos.z - in.draw_depth * DRAW_ORDER_BIAS * out.clip_pos.w;
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out.color = in.color;
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// Dash arc-length, extrapolated over the cap overhang so the pattern
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// stays continuous through a joint.
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out.distance = mix(in.distance_a, in.distance_b, which_end)
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+ ext * hw * u.world_per_pixel;
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out.cap = vec2<f32>(which_end * seg_len + ext * hw, hw * side);
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out.cap_ends = vec3<f32>(seg_len, hw_a, hw_b);
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out.pattern_length = in.pattern_length;
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out.pat0 = in.pat0;
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out.pat1 = in.pat1;
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out.min_elem = min_elem;
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out.align_end = in.align_end;
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out.align_total = in.align_total;
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return out;
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}
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// Returns true if arc-length `dist` falls inside a dash or on a dot.
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fn in_dash(dist: f32, pat_len: f32, p0: vec4<f32>, p1: vec4<f32>, align_end: f32, align_total: f32) -> bool {
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let elems = array<f32, 8>(p0.x, p0.y, p0.z, p0.w, p1.x, p1.y, p1.z, p1.w);
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// Real element count = (index of last non-zero) + 1. Trailing 0.0 slots
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// are padding; a 0.0 within this range is a real dot.
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var count = 0u;
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for (var i = 0u; i < 8u; i++) {
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if elems[i] != 0.0 { count = i + 1u; }
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}
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var d: f32;
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if align_total > 0.0 {
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// "A"-type alignment: the line begins and ends with a solid dash of
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// length `align_end`. Force the two end regions lit, then phase the
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// interior so the element AFTER the first dash resumes exactly at
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// `align_end` (the interior meets each end dash on a gap boundary).
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if dist <= align_end || dist >= align_total - align_end {
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return true;
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}
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var first_dash = 0.0;
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for (var i = 0u; i < count; i++) {
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if elems[i] > 0.0 { first_dash = elems[i]; break; }
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}
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d = ((dist - align_end + first_dash) % pat_len + pat_len) % pat_len;
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} else {
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d = ((dist % pat_len) + pat_len) % pat_len;
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}
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var pos = 0.0f;
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// A dot is a zero-length element: render it as a fixed ~1.5 px mark
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// (half-width ~0.75 px in world units) so it stays visible at any zoom
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// instead of vanishing with its zero world-length. Mirrors the hatch
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// shader's pixel-snapped dot. (#149)
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let dot_half = u.world_per_pixel * 0.75;
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for (var i = 0u; i < count; i++) {
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let elem = elems[i];
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if elem == 0.0 {
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// Dot centred at `pos` (zero length); light a small mark, wrapped
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// around the pattern so a dot at 0 also covers the seam at pat_len.
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let dd = abs(d - pos);
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if min(dd, pat_len - dd) <= dot_half { return true; }
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} else if elem > 0.0 {
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if d >= pos && d < pos + elem { return true; } // inside a dash
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pos += elem;
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} else {
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pos += -elem; // skip a gap
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}
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}
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return false;
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}
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// Round the cap overhang off: outside the segment span only pixels within
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// the end's half-width radius survive, giving round joints and end caps.
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fn cap_clipped(cap: vec2<f32>, cap_ends: vec3<f32>) -> bool {
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if cap.x < 0.0 {
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return length(cap) > cap_ends.y;
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}
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if cap.x > cap_ends.x {
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return length(vec2<f32>(cap.x - cap_ends.x, cap.y)) > cap_ends.z;
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}
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return false;
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}
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@fragment fn fs_main(in: VertexOut) -> @location(0) vec4<f32> {
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if cap_clipped(in.cap, in.cap_ends) {
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discard;
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}
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if in.pattern_length > 0.0 {
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// LOD: once the pattern's smallest feature drops below ~1 px
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// on screen, dash gaps alias / shimmer (or vanish completely)
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// and the user reads the line as solid anyway. Skip the dash
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// test and return solid colour — also saves the per-fragment
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// arc-length math + `discard`.
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if in.min_elem >= u.world_per_pixel {
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if !in_dash(in.distance, in.pattern_length, in.pat0, in.pat1, in.align_end, in.align_total) {
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discard;
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}
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}
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}
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// Transparency display off → force the line opaque.
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let alpha = select(1.0, in.color.a, u.transparency_enable > 0.5);
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return vec4<f32>(in.color.rgb, alpha);
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}
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// Black variant: used for 3D mesh outline edges in filled render modes so the
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// mesh reads as a shaded surface framed by black edges. Keeps the dash/LOD
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// logic identical to `fs_main`; only the RGB is forced to black.
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@fragment fn fs_black(in: VertexOut) -> @location(0) vec4<f32> {
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if cap_clipped(in.cap, in.cap_ends) {
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discard;
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}
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if in.pattern_length > 0.0 {
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if in.min_elem >= u.world_per_pixel {
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if !in_dash(in.distance, in.pattern_length, in.pat0, in.pat1, in.align_end, in.align_total) {
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discard;
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}
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}
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}
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let alpha = select(1.0, in.color.a, u.transparency_enable > 0.5);
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return vec4<f32>(0.0, 0.0, 0.0, alpha);
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}
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