152 lines
6.1 KiB
GLSL
152 lines
6.1 KiB
GLSL
#version 460
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#extension GL_GOOGLE_include_directive : enable
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#extension GL_KHR_shader_subgroup_basic : enable
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#extension GL_KHR_shader_subgroup_arithmetic : enable
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#include "ui-shared.glsl"
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// One workgroup per 8×8 screen tile. The workgroup cooperatively streams the
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// GlyphItem list in chunks of 64 (see ui-shared.glsl), culling each chunk
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// against the tile and compacting survivors — in buffer order — into shared
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// memory; every thread then accumulates over only those survivors.
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layout(push_constant) uniform PC {
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UIDispatchHeader hdr;
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uint fontTextureSlot;
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uint fontSamplerSlot;
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uint _p0;
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uint _p1;
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} pc;
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layout(local_size_x = 8, local_size_y = 8, local_size_z = 1) in;
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// SDF tuning — must match Crafter::FontAtlas::kOnEdgeValue / kPixelDistScale.
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const float ON_EDGE = 128.0 / 255.0;
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const float DIST_SCALE = 32.0;
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shared vec4 s_rect[UI_CHUNK];
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shared vec4 s_uv[UI_CHUNK];
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shared vec4 s_color[UI_CHUNK];
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// Per-glyph constants precomputed once at cooperative-load time and read by the
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// per-pixel inner loop, instead of being recomputed for every pixel × glyph:
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// s_invRectSize = 1.0/rect.zw (turns the per-pixel divide into a multiply)
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// s_band = the SDF AA scale (a divide + two maxes that depend only on
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// the glyph's uv span and rect size — fully loop-invariant)
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shared vec2 s_invRectSize[UI_CHUNK];
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shared float s_band[UI_CHUNK];
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shared uint s_keep[UI_CHUNK];
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shared uint s_order[UI_CHUNK];
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shared uint s_count;
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shared uint s_subTotals[UI_CHUNK]; // per-subgroup survivor totals (carry step)
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// Stable in-order compaction of one chunk's survivors via a per-subgroup
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// exclusive prefix-sum plus a carry across subgroups, so a survivor's slot in
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// s_order[] equals the number of survivors with a smaller local index — buffer
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// (draw) order preserved. Replaces the old lane-0 serial scan. See
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// ui-fused.comp.glsl for the full rationale; the body is identical.
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void uiCompactChunk() {
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uint lid = gl_LocalInvocationIndex;
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uint keep = s_keep[lid];
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uint subPrefix = subgroupExclusiveAdd(keep);
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uint subTotal = subgroupAdd(keep);
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if (subgroupElect())
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s_subTotals[gl_SubgroupID] = subTotal;
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barrier();
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uint base = 0u;
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uint total = 0u;
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for (uint s = 0u; s < gl_NumSubgroups; ++s) {
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uint t = s_subTotals[s];
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if (s < gl_SubgroupID) base += t;
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total += t;
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}
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if (lid == 0u) s_count = total;
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if (keep != 0u)
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s_order[base + subPrefix] = lid;
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}
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void main() {
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ivec2 screenPx;
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bool valid = uiResolveScreenPixel(pc.hdr, screenPx);
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// Defer the destination read-modify-write: a sparse UI leaves most tiles
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// untouched, so only load the pixel when the first surviving glyph blends
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// over it (`loaded`), and only store when something actually touched it.
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// The fused kernel amortizes a single load/store across all categories; the
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// standalone Dispatch* path has no such umbrella and otherwise pays a full
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// read-modify-write per empty tile.
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vec4 dst = vec4(0.0);
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vec2 sp = vec2(0.0);
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bool loaded = false;
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if (valid) sp = vec2(screenPx) + 0.5;
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vec2 tileMin, tileMax;
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uiTileBounds(tileMin, tileMax);
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uint lid = gl_LocalInvocationIndex;
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for (uint base = 0u; base < pc.hdr.itemCount; base += UI_CHUNK) {
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uint idx = base + lid;
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bool keep = false;
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if (idx < pc.hdr.itemCount) {
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s_rect[lid] = uiGlyphHeap[pc.hdr.itemBuffer].items[idx].rect;
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s_uv[lid] = uiGlyphHeap[pc.hdr.itemBuffer].items[idx].uv;
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s_color[lid] = uiGlyphHeap[pc.hdr.itemBuffer].items[idx].color;
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s_invRectSize[lid] = 1.0 / s_rect[lid].zw;
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// Atlas-px per screen-px along this glyph's transform — keeps AA
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// crisp at any rendering size. uvSpan * atlasSize / screenSpan,
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// with FontAtlas::kAtlasSize = 1024. Constant for the whole glyph.
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vec2 uvSpan = s_uv[lid].zw - s_uv[lid].xy;
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vec2 atlasPerScreen = (uvSpan * 1024.0) * s_invRectSize[lid];
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float scalePx = max(atlasPerScreen.x, atlasPerScreen.y);
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// 1-screen-px AA band, expressed in atlas-pixel units of dAtlas.
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s_band[lid] = max(scalePx, 0.0001);
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keep = uiAabbOverlapsTile(s_rect[lid].xy, s_rect[lid].xy + s_rect[lid].zw,
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tileMin, tileMax);
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}
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s_keep[lid] = keep ? 1u : 0u;
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barrier();
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uiCompactChunk();
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barrier();
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if (valid) {
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for (uint j = 0u; j < s_count; ++j) {
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uint c = s_order[j];
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vec2 lo = s_rect[c].xy;
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vec2 hi = s_rect[c].xy + s_rect[c].zw;
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if (sp.x < lo.x || sp.y < lo.y) continue;
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if (sp.x >= hi.x || sp.y >= hi.y) continue;
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vec2 t = (sp - s_rect[c].xy) * s_invRectSize[c];
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vec2 uv = mix(s_uv[c].xy, s_uv[c].zw, t);
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// Font slots are push constants — provably dynamically uniform, so no
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// nonuniformEXT: lets the compiler hoist the descriptor load out of the
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// per-pixel glyph loop and avoid the divergent-descriptor path.
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float sdf = texture(
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sampler2D(uiTextures[pc.fontTextureSlot],
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uiSamplers[pc.fontSamplerSlot]),
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uv
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).r;
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// Distance in atlas-pixels (negative inside the glyph).
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float dAtlas = (ON_EDGE - sdf) * DIST_SCALE;
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// band (the AA scale) was precomputed once per glyph at load.
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float a = clamp(0.5 - dAtlas / s_band[c], 0.0, 1.0);
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if (a <= 0.0) continue;
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vec4 col = s_color[c];
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vec4 src = vec4(col.rgb, col.a * a);
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if (!loaded) {
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dst = imageLoad(uiImages[pc.hdr.outImage], screenPx);
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loaded = true;
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}
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dst = uiBlendOver(dst, src);
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}
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}
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barrier();
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}
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if (loaded) imageStore(uiImages[pc.hdr.outImage], screenPx, dst); // loaded ⇒ valid
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}
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