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

export default /* glsl */`
#ifdef USE_MORPHNORMALS

	objectNormal *= morphTargetBaseInfluence;
	objectNormal += morphNormal0 * morphTargetInfluences[ 0 ];
	objectNormal += morphNormal1 * morphTargetInfluences[ 1 ];
	objectNormal += morphNormal2 * morphTargetInfluences[ 2 ];
	objectNormal += morphNormal3 * morphTargetInfluences[ 3 ];

#endif
`;