#version 430 core

// Campaign V slice V6l: retail's invisible portal depth write, moved out of
// PortalDepthMaskRenderer's inline GLSL string and into the shader tree so both
// backends compile it from one source. The BODY is the one that renderer has
// carried since BR-2 and #117; only how its inputs arrive changed.
//
// Three input moves, each because Vulkan GLSL has no default uniform block:
//
//   uPlaneCount / uPlanes[8]  ->  the TerrainClip UBO at binding=2, which is
//                                 already exactly this shape (int count + 8
//                                 clip-space half-planes) and is already
//                                 declared identically by terrain_modern.vert
//                                 and sky.vert. Retail clips the portal polygon
//                                 on the CPU against the installed view
//                                 (polyClipFinish); we apply the SAME view
//                                 region through gl_ClipDistance, so the depth
//                                 write lands only inside the slice region.
//   uForceFarZ                ->  uRenderPass, the shared push block's pass
//                                 selector. This shader's two passes ARE seal
//                                 (retail maxZ2, true projected depth) and punch
//                                 (retail maxZ1, far-plane z).
//   uDepthBias / EyeCapN      ->  uParamA / uParamB.

layout(location = 0) in vec3 aPos;

// Loose uniforms for the GL dialect. Under Vulkan the compiler drops these
// declarations and the injected preamble #defines each name onto its member of
// the shared 96-byte push block (tools/ShaderCompiler/VulkanGlslPreamble.cs).
uniform mat4  uViewProjection;
uniform int   uRenderPass;   // 0 = seal (retail maxZ2), 1 = punch (retail maxZ1)
uniform float uParamA;       // #117 mark-pass NDC bias toward the viewer
uniform float uParamB;       // #129 eye-span cap x near plane

layout(std140, ACDREAM_UBO_SET binding = 2) uniform TerrainClip {
    int  uTerrainClipCount;
    vec4 uTerrainClipPlanes[8];
};

// Core profile: redeclare gl_PerVertex so writing gl_ClipDistance[] is legal
// (mirrors terrain_modern.vert and sky.vert). Sized 8 to match the
// ClipFrame.MaxPlanes budget and GL's guaranteed GL_MAX_CLIP_DISTANCES >= 8.
out gl_PerVertex {
    vec4  gl_Position;
    float gl_ClipDistance[8];
};

void main()
{
    vec4 clipPos = uViewProjection * vec4(aPos, 1.0);
    for (int i = 0; i < 8; i++)
        gl_ClipDistance[i] = (i < uTerrainClipCount) ? dot(uTerrainClipPlanes[i], clipPos) : 1.0;

    if (uRenderPass == 1)
    {
        clipPos.z = clipPos.w * 0.99999988;   // retail far-z punch constant (0x0059bc90 tail)
    }
    else if (uParamA > 0.0)
    {
        // #117 mark-pass bias, #129 eye-space cap. clipPos.w = eye depth d;
        // an NDC bias b spans ~b*d*d/near meters of eye depth, so the
        // constant-NDC form alone reached METERS at distance (door-shaped
        // leaks through hills/houses). Keep in sync with
        // PortalDepthMaskRenderer.MarkBiasNdc.
        float biasNdc = min(uParamA, uParamB / max(clipPos.w * clipPos.w, 1e-6));
        clipPos.z -= biasNdc * clipPos.w;
    }

    gl_Position = clipPos;
}