#ifdef USE_SHADOWMAP

	#if NUM_DIR_LIGHTS > 0

		uniform sampler2D directionalShadowMap[ NUM_DIR_LIGHTS ];
		varying vec4 vDirectionalShadowCoord[ NUM_DIR_LIGHTS ];

	#endif

	#if NUM_SPOT_LIGHTS > 0

		uniform sampler2D spotShadowMap[ NUM_SPOT_LIGHTS ];
		varying vec4 vSpotShadowCoord[ NUM_SPOT_LIGHTS ];

	#endif

	#if NUM_POINT_LIGHTS > 0

		uniform sampler2D pointShadowMap[ NUM_POINT_LIGHTS ];
		varying vec4 vPointShadowCoord[ NUM_POINT_LIGHTS ];

	#endif

	/*
	#if NUM_RECT_AREA_LIGHTS > 0

		// TODO (abelnation): create uniforms for area light shadows

	#endif
	*/

	float texture2DCompare( sampler2D depths, vec2 uv, float compare ) {

		return step( compare, unpackRGBAToDepth( texture2D( depths, uv ) ) );

	}

	float texture2DShadowLerp( sampler2D depths, vec2 size, vec2 uv, float compare ) {

		const vec2 offset = vec2( 0.0, 1.0 );

		vec2 texelSize = vec2( 1.0 ) / size;
		vec2 centroidUV = floor( uv * size + 0.5 ) / size;

		float lb = texture2DCompare( depths, centroidUV + texelSize * offset.xx, compare );
		float lt = texture2DCompare( depths, centroidUV + texelSize * offset.xy, compare );
		float rb = texture2DCompare( depths, centroidUV + texelSize * offset.yx, compare );
		float rt = texture2DCompare( depths, centroidUV + texelSize * offset.yy, compare );

		vec2 f = fract( uv * size + 0.5 );

		float a = mix( lb, lt, f.y );
		float b = mix( rb, rt, f.y );
		float c = mix( a, b, f.x );

		return c;

	}

	float getShadow( sampler2D shadowMap, vec2 shadowMapSize, float shadowBias, float shadowRadius, vec4 shadowCoord ) {

		float shadow = 1.0;

		shadowCoord.xyz /= shadowCoord.w;
		shadowCoord.z += shadowBias;

		// if ( something && something ) breaks ATI OpenGL shader compiler
		// if ( all( something, something ) ) using this instead

		bvec4 inFrustumVec = bvec4 ( shadowCoord.x >= 0.0, shadowCoord.x <= 1.0, shadowCoord.y >= 0.0, shadowCoord.y <= 1.0 );
		bool inFrustum = all( inFrustumVec );

		bvec2 frustumTestVec = bvec2( inFrustum, shadowCoord.z <= 1.0 );

		bool frustumTest = all( frustumTestVec );

		if ( frustumTest ) {

		#if defined( SHADOWMAP_TYPE_PCF )

			vec2 texelSize = vec2( 1.0 ) / shadowMapSize;

			float dx0 = - texelSize.x * shadowRadius;
			float dy0 = - texelSize.y * shadowRadius;
			float dx1 = + texelSize.x * shadowRadius;
			float dy1 = + texelSize.y * shadowRadius;

			shadow = (
				texture2DCompare( shadowMap, shadowCoord.xy + vec2( dx0, dy0 ), shadowCoord.z ) +
				texture2DCompare( shadowMap, shadowCoord.xy + vec2( 0.0, dy0 ), shadowCoord.z ) +
				texture2DCompare( shadowMap, shadowCoord.xy + vec2( dx1, dy0 ), shadowCoord.z ) +
				texture2DCompare( shadowMap, shadowCoord.xy + vec2( dx0, 0.0 ), shadowCoord.z ) +
				texture2DCompare( shadowMap, shadowCoord.xy, shadowCoord.z ) +
				texture2DCompare( shadowMap, shadowCoord.xy + vec2( dx1, 0.0 ), shadowCoord.z ) +
				texture2DCompare( shadowMap, shadowCoord.xy + vec2( dx0, dy1 ), shadowCoord.z ) +
				texture2DCompare( shadowMap, shadowCoord.xy + vec2( 0.0, dy1 ), shadowCoord.z ) +
				texture2DCompare( shadowMap, shadowCoord.xy + vec2( dx1, dy1 ), shadowCoord.z )
			) * ( 1.0 / 9.0 );

		#elif defined( SHADOWMAP_TYPE_PCF_SOFT )

			vec2 texelSize = vec2( 1.0 ) / shadowMapSize;

			float dx0 = - texelSize.x * shadowRadius;
			float dy0 = - texelSize.y * shadowRadius;
			float dx1 = + texelSize.x * shadowRadius;
			float dy1 = + texelSize.y * shadowRadius;

			shadow = (
				texture2DShadowLerp( shadowMap, shadowMapSize, shadowCoord.xy + vec2( dx0, dy0 ), shadowCoord.z ) +
				texture2DShadowLerp( shadowMap, shadowMapSize, shadowCoord.xy + vec2( 0.0, dy0 ), shadowCoord.z ) +
				texture2DShadowLerp( shadowMap, shadowMapSize, shadowCoord.xy + vec2( dx1, dy0 ), shadowCoord.z ) +
				texture2DShadowLerp( shadowMap, shadowMapSize, shadowCoord.xy + vec2( dx0, 0.0 ), shadowCoord.z ) +
				texture2DShadowLerp( shadowMap, shadowMapSize, shadowCoord.xy, shadowCoord.z ) +
				texture2DShadowLerp( shadowMap, shadowMapSize, shadowCoord.xy + vec2( dx1, 0.0 ), shadowCoord.z ) +
				texture2DShadowLerp( shadowMap, shadowMapSize, shadowCoord.xy + vec2( dx0, dy1 ), shadowCoord.z ) +
				texture2DShadowLerp( shadowMap, shadowMapSize, shadowCoord.xy + vec2( 0.0, dy1 ), shadowCoord.z ) +
				texture2DShadowLerp( shadowMap, shadowMapSize, shadowCoord.xy + vec2( dx1, dy1 ), shadowCoord.z )
			) * ( 1.0 / 9.0 );

		#else // no percentage-closer filtering:

			shadow = texture2DCompare( shadowMap, shadowCoord.xy, shadowCoord.z );

		#endif

		}

		return shadow;

	}

	// cubeToUV() maps a 3D direction vector suitable for cube texture mapping to a 2D
	// vector suitable for 2D texture mapping. This code uses the following layout for the
	// 2D texture:
	//
	// xzXZ
	//  y Y
	//
	// Y - Positive y direction
	// y - Negative y direction
	// X - Positive x direction
	// x - Negative x direction
	// Z - Positive z direction
	// z - Negative z direction
	//
	// Source and test bed:
	// https://gist.github.com/tschw/da10c43c467ce8afd0c4

	vec2 cubeToUV( vec3 v, float texelSizeY ) {

		// Number of texels to avoid at the edge of each square

		vec3 absV = abs( v );

		// Intersect unit cube

		float scaleToCube = 1.0 / max( absV.x, max( absV.y, absV.z ) );
		absV *= scaleToCube;

		// Apply scale to avoid seams

		// two texels less per square (one texel will do for NEAREST)
		v *= scaleToCube * ( 1.0 - 2.0 * texelSizeY );

		// Unwrap

		// space: -1 ... 1 range for each square
		//
		// #X##		dim    := ( 4 , 2 )
		//  # #		center := ( 1 , 1 )

		vec2 planar = v.xy;

		float almostATexel = 1.5 * texelSizeY;
		float almostOne = 1.0 - almostATexel;

		if ( absV.z >= almostOne ) {

			if ( v.z > 0.0 )
				planar.x = 4.0 - v.x;

		} else if ( absV.x >= almostOne ) {

			float signX = sign( v.x );
			planar.x = v.z * signX + 2.0 * signX;

		} else if ( absV.y >= almostOne ) {

			float signY = sign( v.y );
			planar.x = v.x + 2.0 * signY + 2.0;
			planar.y = v.z * signY - 2.0;

		}

		// Transform to UV space

		// scale := 0.5 / dim
		// translate := ( center + 0.5 ) / dim
		return vec2( 0.125, 0.25 ) * planar + vec2( 0.375, 0.75 );

	}

	float getPointShadow( sampler2D shadowMap, vec2 shadowMapSize, float shadowBias, float shadowRadius, vec4 shadowCoord, float shadowCameraNear, float shadowCameraFar ) {

		vec2 texelSize = vec2( 1.0 ) / ( shadowMapSize * vec2( 4.0, 2.0 ) );

		// for point lights, the uniform @vShadowCoord is re-purposed to hold
		// the vector from the light to the world-space position of the fragment.
		vec3 lightToPosition = shadowCoord.xyz;

		// dp = normalized distance from light to fragment position
		float dp = ( length( lightToPosition ) - shadowCameraNear ) / ( shadowCameraFar - shadowCameraNear ); // need to clamp?
		dp += shadowBias;

		// bd3D = base direction 3D
		vec3 bd3D = normalize( lightToPosition );

		#if defined( SHADOWMAP_TYPE_PCF ) || defined( SHADOWMAP_TYPE_PCF_SOFT )

			vec2 offset = vec2( - 1, 1 ) * shadowRadius * texelSize.y;

			return (
				texture2DCompare( shadowMap, cubeToUV( bd3D + offset.xyy, texelSize.y ), dp ) +
				texture2DCompare( shadowMap, cubeToUV( bd3D + offset.yyy, texelSize.y ), dp ) +
				texture2DCompare( shadowMap, cubeToUV( bd3D + offset.xyx, texelSize.y ), dp ) +
				texture2DCompare( shadowMap, cubeToUV( bd3D + offset.yyx, texelSize.y ), dp ) +
				texture2DCompare( shadowMap, cubeToUV( bd3D, texelSize.y ), dp ) +
				texture2DCompare( shadowMap, cubeToUV( bd3D + offset.xxy, texelSize.y ), dp ) +
				texture2DCompare( shadowMap, cubeToUV( bd3D + offset.yxy, texelSize.y ), dp ) +
				texture2DCompare( shadowMap, cubeToUV( bd3D + offset.xxx, texelSize.y ), dp ) +
				texture2DCompare( shadowMap, cubeToUV( bd3D + offset.yxx, texelSize.y ), dp )
			) * ( 1.0 / 9.0 );

		#else // no percentage-closer filtering

			return texture2DCompare( shadowMap, cubeToUV( bd3D, texelSize.y ), dp );

		#endif

	}

#endif
