<!-- NEW3 — TEST 3 · THE RIVER'S JOURNEY · part 354 -->
p float;
			precision highp int;

			varying vec3 vOutputDirection;

			uniform sampler2D envMap;
			uniform float roughness;
			uniform float mipInt;

			#define ENVMAP_TYPE_CUBE_UV
			#include <cube_uv_reflection_fragment>

			#define PI 3.14159265359

			// Van der Corput radical inverse
			float radicalInverse_VdC(uint bits) {
				bits = (bits << 16u) | (bits >> 16u);
				bits = ((bits & 0x55555555u) << 1u) | ((bits & 0xAAAAAAAAu) >> 1u);
				bits = ((bits & 0x33333333u) << 2u) | ((bits & 0xCCCCCCCCu) >> 2u);
				bits = ((bits & 0x0F0F0F0Fu) << 4u) | ((bits & 0xF0F0F0F0u) >> 4u);
				bits = ((bits & 0x00FF00FFu) << 8u) | ((bits & 0xFF00FF00u) >> 8u);
				return float(bits) * 2.3283064365386963e-10; // / 0x100000000
			}

			// Hammersley sequence
			vec2 hammersley(uint i, uint N) {
				return vec2(float(i) / float(N), radicalInverse_VdC(i));
			}

			// GGX VNDF importance sampling (Eric Heitz 2018)
			// "Sampling the GGX Distribution of Visible Normals"
			// https://jcgt.org/published/0007/04/01/
			vec3 importanceSampleGGX_VNDF(vec2 Xi, vec3 V, float roughness) {
				float alpha = roughness * roughness;

				// Section 4.1: Orthonormal basis
				vec3 T1 = vec3(1.0, 0.0, 0.0);
				vec3 T2 = cross(V, T1);

				// Section 4.2: Parameterization of projected area
				float r = sqrt(Xi.x);
				float phi = 2.0 * PI * Xi.y;
				float t1 = r * cos(phi);
				float t2 = r * sin(phi);
				float s = 0.5 * (1.0 + V.z);
				t2 = (1.0 - s) * sqrt(1.0 - t1 * t1) + s * t2;

				// Section 4.3: Reprojection onto hemisphere
				vec3 Nh = t1 * T1 + t2 * T2 + sqrt(max(0.0, 1.0 - t1 * t1 - t2 * t2)) * V;

				// Section 3.4: Transform back to ellipsoid configuration
				return normalize(vec3(alpha * Nh.x, alpha * Nh.y, max(0.0, Nh.z)));
			}

			void main() {
				vec3 N = normalize(vOutputDirection);
				vec3 V = N; // Assume view direction equals normal for pre-filtering

				vec3 prefilteredColor = vec3(0.0);
				float totalWeight = 0.0;

				// For very low roughness, just sample the environment directly
				if (roughness < 0.001) {
					gl_FragColor = vec4(bilinearCubeUV(envMap, N, mipInt), 1.0);
					return;
				}

				// Tangent space basis for VNDF sampling
				vec3 up = abs(N.z) < 0.999 ? vec3(0.0, 0.0, 1.0) : vec3(1.0, 0.0, 0.0);
				vec3 tangent = normalize(cross(up, N));
				vec3 bitangent = cross(N, tangent);

				for(uint i = 0u; i < uint(GGX_SAMPLES); i++) {
					vec2 Xi = hammersley(i, uint(GGX_SAMPLES));

					// For PMREM, V = N, so in tangent space V is always (0, 0, 1)
					vec3 H_tangent = importanceSampleGGX_VNDF(Xi, vec3(0.0, 0.0, 1.0), roughness);

					// Transform H back to world space
					vec3 H = normalize(tangent * H_tangent.x + bitangent * H_tangent.y + N * H_tangent.z);
					vec3 L = normalize(2.0 * dot(V, H) * H - V);

					float NdotL = max(dot(N, L), 0.0);

					if(NdotL > 0.0) {
						// Sample environment at fixed mip level
						// VNDF importance sampling handles the distribution filtering
						vec3 sampleColor = bilinearCubeUV(envMap, L, mipInt);

						// Weight by NdotL for the split-sum approximation
						// VNDF PDF naturally accounts for the visible microfacet distribution
						prefilteredColor += sampleColor * NdotL;
						totalWeight += NdotL;
					}
				}

				if (totalWeight > 0.0) {
					prefilteredColor = prefilteredColor / totalWeight;
				}

				gl_FragColor = vec4(prefilteredColor, 1.0);
			}
		`,

		blending: NoBlending,
		depthTest: false,
		depthWrite: false

	} );

	return shaderMaterial;

}

function _getBlurShader( lodMax, width, height ) {

	const shaderMaterial = new ShaderMaterial( {

		name: 'SphericalGaussianBlur',

		defines: {
			'SAMPLES': BLUR_SAMPLES,
			'CUBEUV_TEXEL_WIDTH': 1.0 / width,
			'CUBEUV_TEXEL_HEIGHT': 1.0 / height,
			'CUBEUV_MAX_MIP': `${lodMax}.0`,
		},

		uniforms: {
			'envMap': { value: null },
			'sigma': { value: 0 },
			'mipInt': { value: 0 },
		},

		vertexShader: _getCommonVertexShader(),

		fragmentShader: /* glsl */`

			precision highp float;
			precision highp int;

			varying vec3 vOutputDirection;

			uniform sampler2D envMap;
			uniform float sigma;
			uniform float mipInt;

			#define ENVMAP_TYPE_CUBE_UV
			#include <cube_uv_reflection_fragment>

			#define PI 3.14159265359
			#define GOLDEN_ANGLE 2.39996322973

			void main() {

				if ( sigma == 0.0 ) {

					gl_FragColor = vec4( bilinearCubeUV( envMap, vOutputDirection, mipInt ), 1.0 );
					return;

				}

				vec3 outputDirection = normalize( vOutputDirection );

				vec3 up = abs( outputDirection.z ) < 0.999 ? vec3( 0.0, 0.0, 1.0 ) : vec3( 1.0, 0.0, 0.0 );
				vec3 tangent = normalize( cross( up, outputDirection ) );
				vec3 bitangent = cross( outputDirection, tangent );

				// Truncate the kernel at three standard deviations or at the antipode.
				float thetaMax = min( 3.0 * sigma, PI );
				float truncation = 1.0 - exp( - 0.5 * thetaMax * thetaMax / ( sigma * sigma ) );

				vec3 accumColor = vec3( 0.0