/**
 * 알파채널 경계 기반 BoxShadow 셰이더
 *
 * image/sprite 객체에서 style.boxShadow* 를
 * 이미지 사각형이 아닌 알파채널 외곽에 그림자를 렌더링합니다.
 *
 * 동작 방식:
 *   - 현재 픽셀이 이미지 불투명 영역 위 → discard (그림자는 이미지 뒤에 숨겨짐)
 *   - 그림자 소스 위치 = CSS offset 역변환: shadowSrcP = p - vec2(offsetX, -offsetY)
 *   - blur: Gaussian 링 샘플링 (1 center + 3 rings × 8 = 25 samples) 으로 소프트 블러 근사
 *   - spread: effectiveBlur = blur + spread 로 그림자 확장 처리
 */
export declare const alphaShadowVertex = "\n  attribute vec2 position;\n  attribute vec2 uv;\n  uniform mat4 uModelMatrix;\n  uniform mat4 uViewMatrix;\n  uniform mat4 uProjectionMatrix;\n  varying vec2 vUV;\n\n  void main() {\n    vUV = uv;\n    gl_Position = uProjectionMatrix * uViewMatrix * uModelMatrix * vec4(position, 0.0, 1.0);\n  }\n";
export declare const alphaShadowFragment = "\n  precision highp float;\n\n  uniform sampler2D uTexture;\n  uniform vec4  uColor;          // \uADF8\uB9BC\uC790 \uC0C9\uC0C1 RGBA\n  uniform float uOpacity;        // \uC804\uCCB4 \uBD88\uD22C\uBA85\uB3C4\n  uniform vec2  uQuadSize;       // \uADF8\uB9BC\uC790 \uCFFC\uB4DC \uD06C\uAE30 (world units)\n  uniform vec2  uImageSize;      // \uC774\uBBF8\uC9C0 \uD45C\uC2DC \uD06C\uAE30 (world units)\n  uniform vec2  uOffset;         // CSS \uADF8\uB9BC\uC790 offset [x, y] (+y = down)\n  uniform float uBlur;           // \uBE14\uB7EC \uBC18\uACBD (world units)\n  uniform float uSpread;         // \uD655\uC7A5 \uBC18\uACBD (world units)\n  uniform float uAlphaThreshold; // \uD53D\uC140\uC744 \uBD88\uD22C\uBA85\uC73C\uB85C \uD310\uB2E8\uD560 \uCD5C\uC19F\uAC12\n\n  varying vec2 vUV;\n\n  uniform vec2 uUVOffset;\n  uniform vec2 uUVScale;\n\n  // \uC774\uBBF8\uC9C0 UV \uBC94\uC704 \uD074\uB7A8\uD504 \uCCB4\uD06C\n  bool inUV(vec2 uv) {\n    return uv.x >= 0.0 && uv.x <= 1.0 && uv.y >= 0.0 && uv.y <= 1.0;\n  }\n\n  // \uC6D4\uB4DC \uC88C\uD45C \u2192 \uC774\uBBF8\uC9C0 UV \uBCC0\uD658\n  vec2 worldToImageUV(vec2 worldPos) {\n    return (worldPos + uImageSize * 0.5) / uImageSize;\n  }\n\n  void main() {\n    // \uADF8\uB9BC\uC790 \uCFFC\uB4DC \uC911\uC2EC \uAE30\uC900\uC758 \uD604\uC7AC \uD53D\uC140 \uC6D4\uB4DC \uC88C\uD45C\n    vec2 p = (vUV - 0.5) * uQuadSize;\n\n    // \uC774\uBBF8\uC9C0 \uBD88\uD22C\uBA85 \uC601\uC5ED \uC704\uB294 \uADF8\uB9BC\uC790 \uB80C\uB354 \uC81C\uC678\n    vec2 imgUV = worldToImageUV(p);\n    if (inUV(imgUV)) {\n      vec2 texUV = imgUV * uUVScale + uUVOffset;\n      if (texture2D(uTexture, texUV).a > uAlphaThreshold) {\n        discard;\n      }\n    }\n\n    // CSS \uADF8\uB9BC\uC790 offset \uC5ED\uBCC0\uD658: WebGL +y = up, CSS +y = down\n    vec2 shadowSrcP = p - vec2(uOffset.x, -uOffset.y);\n\n    // blur + spread \uB97C \uD569\uC0B0\uD558\uC5EC \uC720\uD6A8 \uBE14\uB7EC \uBC18\uACBD \uACC4\uC0B0\n    float effectiveBlur = uBlur + uSpread;\n\n    // \u2500\u2500 Gaussian \uB9C1 \uC0D8\uD50C\uB9C1 \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\n    // 1 center + 3 rings \u00D7 8 samples = 25 samples\n    float PI2 = 6.28318;\n    float accAlpha = 0.0;\n    float totalWeight = 0.0;\n\n    // Ring 0: \uC911\uC2EC \uC0D8\uD50C (\uAC00\uC911\uCE58 \uCD5C\uB300)\n    {\n      float w = 1.0;\n      vec2 sUV = worldToImageUV(shadowSrcP);\n      if (inUV(sUV)) {\n        vec2 texUV = sUV * uUVScale + uUVOffset;\n        accAlpha += texture2D(uTexture, texUV).a * w;\n      }\n      totalWeight += w;\n    }\n\n    // Rings 1\u20133: \uC6D0\uC8FC \uBC29\uD5A5 8 \uC0D8\uD50C\uC529, Gaussian \uAC00\uC911\uCE58\n    for (int ring = 1; ring <= 3; ring++) {\n      float r = float(ring) * effectiveBlur / 3.0;\n      float sigma = max(effectiveBlur / 2.0, 0.001);\n      float w = exp(-r * r / (2.0 * sigma * sigma));\n\n      for (int i = 0; i < 8; i++) {\n        float angle = float(i) / 8.0 * PI2;\n        vec2 s = shadowSrcP + vec2(cos(angle), sin(angle)) * r;\n        vec2 sUV = worldToImageUV(s);\n        if (inUV(sUV)) {\n          vec2 texUV = sUV * uUVScale + uUVOffset;\n          accAlpha += texture2D(uTexture, texUV).a * w;\n        }\n        totalWeight += w;\n      }\n    }\n\n    float shadowAlpha = accAlpha / max(totalWeight, 0.001);\n    if (shadowAlpha <= uAlphaThreshold) discard;\n\n    float finalA = uColor.a * uOpacity * shadowAlpha;\n    gl_FragColor = vec4(uColor.rgb * finalA, finalA);\n  }\n";