export default /* glsl */`

#ifdef USE_GRADIENTMAP

	uniform sampler2D gradientMap;

#endif

vec3 getGradientIrradiance( vec3 normal, vec3 lightDirection ) {

	// dotNL will be from -1.0 to 1.0
	float dotNL = dot( normal, lightDirection );
	vec2 coord = vec2( dotNL * 0.5 + 0.5, 0.0 );

	#ifdef USE_GRADIENTMAP

		return vec3( texture2D( gradientMap, coord ).r );

	#else

		vec2 fw = fwidth( coord ) * 0.5;
		return mix( vec3( 0.7 ), vec3( 1.0 ), smoothstep( 0.7 - fw.x, 0.7 + fw.x, coord.x ) );

	#endif

}
`;