acdream/src/AcDream.App/Rendering/Shaders/sky.frag

#version 430 core
#extension GL_ARB_bindless_texture : require

in vec2  vTex;
in vec3  vTint;
in float vFogFactor;   // 1 = no fog, 0 = full fog color
out vec4 fragColor;

// Campaign V slice V6e: the sky's texture is now read through the shared table
// (ACDREAM_SAMPLE_2D, injected by tools/ShaderCompiler/VulkanGlslPreamble.cs)
// rather than a `uniform sampler2D` bound to texture unit 0. Vulkan has no
// default uniform block to declare a loose sampler in, and set 2 is where
// every sampled texture lives.
//
// The wrap mode travels WITH the slot: SkyRenderer registers a distinct table
// entry per (texture, sampler) pair, so the per-submesh Repeat-vs-ClampToEdge
// choice that used to be a glBindSampler call is now which slot it asks for.
// That is the same shape the Vulkan table has, where a table entry is a
// combined image sampler.
uniform uint uTextureIndexA;

// The per-draw block sky.vert declares. A uniform block must be declared
// identically in every stage of a program that names it — the same rule the
// SceneLighting block below has always followed — so the whole thing appears
// here even though the fragment stage reads only the last three scalars.
layout(std140, ACDREAM_UBO_SET binding = 4) uniform SkyParams {
    mat4  uModel;
    mat4  uSkyView;
    mat4  uSkyProjection;
    vec3  uAmbientColor;
    float uEmissive;
    vec3  uSunColor;
    float uDiffuseFactor;
    vec3  uSunDir;
    float uTransparency;
    vec2  uUvScroll;
    float uApplyFog;
    float uSurfOpacity;
};

struct Light {
    vec4 posAndKind;
    vec4 dirAndRange;
    vec4 colorAndIntensity;
    vec4 coneAngleEtc;
};
layout(std140, ACDREAM_UBO_SET binding = 1) uniform SceneLighting {
    Light uLights[8];
    vec4  uCellAmbient;
    vec4  uFogParams;
    vec4  uFogColor;
    vec4  uCameraAndTime;
};

void main() {
    vec4 sampled = ACDREAM_SAMPLE_2D(uTextureIndexA, vTex);

    vec3 rgb = sampled.rgb * vTint;

    // SHOULD-FIX S2/mech NOTE N-3 (OP4 review-fix round, 2026-08-11):
    // PlayerOption DisableDistanceFog forces FogMode.Off (uFogParams.w
    // == 0) — mesh_modern.frag/terrain_modern.frag both gate their own
    // fog blend on this same word (`if (mode == 0) return lit;`), but the
    // sky dome's blend here read only uApplyFog (the CPU per-submesh
    // "is this layer foggable at all" flag) and never uFogParams.w, so
    // toggling the option stopped terrain/objects fading into fog while
    // the dome's horizon band kept blending toward fog color.
    int fogMode = int(uFogParams.w);
    if (uApplyFog > 0.5 && fogMode != 0) {
        const float SKY_FOG_FLOOR = 0.2;
        float skyFogFactor = max(vFogFactor, SKY_FOG_FLOOR);
        rgb = mix(uFogColor.rgb, rgb, skyFogFactor);
    }

    float flash = uFogParams.z;
    rgb += flash * vec3(1.5, 1.5, 1.8);

    float cap = mix(1.0, 3.0, clamp(flash, 0.0, 1.0));
    rgb = min(rgb, vec3(cap));

    float a = sampled.a * (1.0 - uTransparency) * uSurfOpacity;
    if (a < 0.01) discard;
    fragColor = vec4(rgb, a);
}