Crafter.Graphics/shaders/ui-text.comp.glsl

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2026-05-02 21:08:20 +02:00
#version 460
#extension GL_GOOGLE_include_directive : enable
#include "ui-shared.glsl"
// One workgroup per 8×8 screen tile. Iterates every glyph in order; each
// pixel keeps a local accumulator so order in the buffer == draw order.
layout(push_constant) uniform PC {
UIDispatchHeader hdr;
uint fontTextureSlot;
uint fontSamplerSlot;
uint _p0;
uint _p1;
} pc;
layout(local_size_x = 8, local_size_y = 8, local_size_z = 1) in;
// SDF tuning — must match Crafter::FontAtlas::kOnEdgeValue / kPixelDistScale.
const float ON_EDGE = 128.0 / 255.0;
const float DIST_SCALE = 32.0;
void main() {
ivec2 screenPx;
if (!uiResolveScreenPixel(pc.hdr, screenPx)) return;
vec4 dst = imageLoad(uiImages[pc.hdr.outImage], screenPx);
vec2 sp = vec2(screenPx) + 0.5;
for (uint i = 0u; i < pc.hdr.itemCount; ++i) {
GlyphItem it = LoadGlpyhtem(pc.hdr.itemBuffer, i);
vec2 lo = it.rect.xy;
vec2 hi = it.rect.xy + it.rect.zw;
if (sp.x < lo.x || sp.y < lo.y) continue;
if (sp.x >= hi.x || sp.y >= hi.y) continue;
vec2 t = (sp - it.rect.xy) / it.rect.zw;
vec2 uv = mix(it.uv.xy, it.uv.zw, t);
float sdf = texture(
sampler2D(uiTextures[nonuniformEXT(pc.fontTextureSlot)],
uiSamplers[nonuniformEXT(pc.fontSamplerSlot)]),
uv
).r;
// Distance in atlas-pixels (negative inside the glyph).
float dAtlas = (ON_EDGE - sdf) * DIST_SCALE;
// Atlas-px per screen-px along this glyph's transform — keeps AA crisp
// at any rendering size. uvSpan * atlasSize / screenSpan.
vec2 uvSpan = it.uv.zw - it.uv.xy;
// FontAtlas::kAtlasSize = 1024.
vec2 atlasPerScreen = (uvSpan * 1024.0) / it.rect.zw;
float scalePx = max(atlasPerScreen.x, atlasPerScreen.y);
// 1-screen-px AA band, expressed in atlas-pixel units of dAtlas.
float band = max(scalePx, 0.0001);
float a = clamp(0.5 - dAtlas / band, 0.0, 1.0);
if (a <= 0.0) continue;
vec4 src = vec4(it.color.rgb, it.color.a * a);
dst = uiBlendOver(dst, src);
}
imageStore(uiImages[pc.hdr.outImage], screenPx, dst);
}