simplified soft shadow shader

docs/api/en/lights/shadows/LightShadow.html

@@ -74,8 +74,8 @@
 
 			High values will cause unwanted banding effects in the shadows - a greater [page:.mapSize mapSize]
 			will allow for a higher value to be used here before these effects become visible.<br />
-			If [page:WebGLRenderer.shadowMap.type] is set to [page:Renderer PCFSoftShadowMap], it is recommended to
-			leave radius at 1 and increase softness by decreasing [page:.mapSize mapSize] instead.<br /><br />
+			If [page:WebGLRenderer.shadowMap.type] is set to [page:Renderer PCFSoftShadowMap], radius has 
+			no effect and it is recommended to increase softness by decreasing [page:.mapSize mapSize] instead.<br /><br />
 
 			Note that this has no effect if the [page:WebGLRenderer.shadowMap.type] is set to [page:Renderer BasicShadowMap].
 		</p>

docs/api/zh/lights/shadows/LightShadow.html

@@ -69,8 +69,8 @@
 			将此值设置为大于1的值将模糊阴影的边缘。<br />
 
 			较高的值会在阴影中产生不必要的条带效果 - 更大的[page:.mapSize mapSize]将允许在这些效果变得可见之前使用更高的值。<br />
-			If [page:WebGLRenderer.shadowMap.type] is set to [page:Renderer PCFSoftShadowMap], it is recommended to
-			leave radius at 1 and increase softness by decreasing [page:.mapSize mapSize] instead.<br /><br />
+			If [page:WebGLRenderer.shadowMap.type] is set to [page:Renderer PCFSoftShadowMap], radius has 
+			no effect and it is recommended to increase softness by decreasing [page:.mapSize mapSize] instead.<br /><br />
 			
 			请注意，如果[page：WebGLRenderer.shadowMap.type]设置为[page:Renderer BasicShadowMap]，将会无效。
 		</p>

src/renderers/shaders/ShaderChunk/shadowmap_pars_fragment.glsl.js

@@ -63,28 +63,6 @@ export default /* glsl */`
 
 	}
 
-	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 ) + 0.5 ) * texelSize;
-
-		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;
@@ -140,22 +118,37 @@ export default /* glsl */`
 		#elif defined( SHADOWMAP_TYPE_PCF_SOFT )
 
 			vec2 texelSize = vec2( 1.0 ) / shadowMapSize;
+			float dx = texelSize.x;
+			float dy = texelSize.y;
 
-			float dx0 = - texelSize.x * shadowRadius;
-			float dy0 = - texelSize.y * shadowRadius;
-			float dx1 = + texelSize.x * shadowRadius;
-			float dy1 = + texelSize.y * shadowRadius;
+			vec2 uv = shadowCoord.xy;
+			vec2 f = fract( uv * shadowMapSize + 0.5 );
+			uv -= f * texelSize;
 
 			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 )
+				texture2DCompare( shadowMap, uv, shadowCoord.z ) +
+				texture2DCompare( shadowMap, uv + vec2( dx, 0.0 ), shadowCoord.z ) +
+				texture2DCompare( shadowMap, uv + vec2( 0.0, dy ), shadowCoord.z ) +
+				texture2DCompare( shadowMap, uv + texelSize, shadowCoord.z ) +
+				mix( texture2DCompare( shadowMap, uv + vec2( -dx, 0.0 ), shadowCoord.z ), 
+					 texture2DCompare( shadowMap, uv + vec2( 2.0 * dx, 0.0 ), shadowCoord.z ),
+					 f.x ) +
+				mix( texture2DCompare( shadowMap, uv + vec2( -dx, dy ), shadowCoord.z ), 
+					 texture2DCompare( shadowMap, uv + vec2( 2.0 * dx, dy ), shadowCoord.z ),
+					 f.x ) +
+				mix( texture2DCompare( shadowMap, uv + vec2( 0.0, -dy ), shadowCoord.z ), 
+					 texture2DCompare( shadowMap, uv + vec2( 0.0, 2.0 * dy ), shadowCoord.z ),
+					 f.y ) +
+				mix( texture2DCompare( shadowMap, uv + vec2( dx, -dy ), shadowCoord.z ), 
+					 texture2DCompare( shadowMap, uv + vec2( dx, 2.0 * dy ), shadowCoord.z ),
+					 f.y ) +
+				mix( mix( texture2DCompare( shadowMap, uv + vec2( -dx, -dy ), shadowCoord.z ), 
+						  texture2DCompare( shadowMap, uv + vec2( 2.0 * dx, -dy ), shadowCoord.z ),
+						  f.x ),
+					 mix( texture2DCompare( shadowMap, uv + vec2( -dx, 2.0 * dy ), shadowCoord.z ), 
+						  texture2DCompare( shadowMap, uv + + vec2( 2.0 * dx, 2.0 * dy ), shadowCoord.z ),
+						  f.x ),
+					 f.y )
 			) * ( 1.0 / 9.0 );
 
 		#elif defined( SHADOWMAP_TYPE_VSM )