three.js/src/renderers/shaders/ShaderChunk/transmission_fragment.glsl.js

export default /* glsl */`
#ifdef USE_TRANSMISSION

	material.transmission = transmission;
	material.transmissionAlpha = 1.0;
	material.thickness = thickness;
	material.attenuationDistance = attenuationDistance;
	material.attenuationColor = attenuationColor;

	#ifdef USE_TRANSMISSIONMAP

		material.transmission *= texture2D( transmissionMap, vUv ).r;

	#endif

	#ifdef USE_THICKNESSMAP

		material.thickness *= texture2D( thicknessMap, vUv ).g;

	#endif

	vec3 pos = vWorldPosition;
	vec3 v = normalize( cameraPosition - pos );
	vec3 n = inverseTransformDirection( normal, viewMatrix );

	vec4 transmission = getIBLVolumeRefraction(
		n, v, roughnessFactor, material.diffuseColor, material.specularColor, material.specularF90,
		pos, modelMatrix, viewMatrix, projectionMatrix, material.ior, material.thickness,
		material.attenuationColor, material.attenuationDistance );

	material.transmissionAlpha = mix( material.transmissionAlpha, transmission.a, material.transmission );

	totalDiffuse = mix( totalDiffuse, transmission.rgb, material.transmission );

#endif
`;