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

#if NUM_CLIPPING_PLANES > 0

	for ( int i = 0; i < UNION_CLIPPING_PLANES; ++ i ) {

		vec4 plane = clippingPlanes[ i ];
		if ( dot( vViewPosition, plane.xyz ) > plane.w ) discard;

	}
		
	#if UNION_CLIPPING_PLANES < NUM_CLIPPING_PLANES

		bool clipped = true;
		for ( int i = UNION_CLIPPING_PLANES; i < NUM_CLIPPING_PLANES; ++ i ) {
			vec4 plane = clippingPlanes[ i ];
			clipped = ( dot( vViewPosition, plane.xyz ) > plane.w ) && clipped;
		}

		if ( clipped ) discard;
	
	#endif

#endif