Add maskFunction setting

Addresses #529

src/effects/DepthOfFieldEffect.js

@@ -182,8 +182,8 @@ export class DepthOfFieldEffect extends Effect {
 
 		this.maskPass = new ShaderPass(new MaskMaterial(this.renderTargetCoC.texture));
 		const maskMaterial = this.maskPass.fullscreenMaterial;
-		maskMaterial.maskFunction = MaskFunction.MULTIPLY_RGB;
 		maskMaterial.colorChannel = ColorChannel.GREEN;
+		this.maskFunction = MaskFunction.MULTIPLY_RGB;
 
 		/**
 		 * A bokeh blur pass for the foreground colors.
@@ -266,6 +266,30 @@ export class DepthOfFieldEffect extends Effect {
 
 	}
 
+	/**
+	 * The mask function. Default is `MULTIPLY_RGB`.
+	 *
+	 * @type {MaskFunction}
+	 */
+
+	get maskFunction() {
+
+		return this.maskPass.fullscreenMaterial.maskFunction;
+
+	}
+
+	set maskFunction(value) {
+
+		if(this.maskFunction !== value) {
+
+			this.defines.set("MASK_FUNCTION", value.toFixed(0));
+			this.maskPass.fullscreenMaterial.maskFunction = value;
+			this.setChanged();
+
+		}
+
+	}
+
 	/**
 	 * The circle of confusion material.
 	 *

src/effects/glsl/depth-of-field.frag

@@ -19,12 +19,18 @@ void mainImage(const in vec4 inputColor, const in vec2 uv, const in float depth,
 	vec4 colorNear = texture2D(nearColorBuffer, uv);
 	vec4 colorFar = texture2D(farColorBuffer, uv);
 
-	vec2 cocNearFar = vec2(
-		texture2D(nearCoCBuffer, uv).r,
-		texture2D(farCoCBuffer, uv).g
-	);
+	#if MASK_FUNCTION == 1
 
-	cocNearFar = min(cocNearFar * scale, 1.0);
+		// Use the CoC from the far color buffer's alpha channel.
+		vec2 cocNearFar = vec2(texture2D(nearCoCBuffer, uv).r, colorFar.a);
+		cocNearFar.x = min(cocNearFar.x * scale, 1.0);
+
+	#else
+
+		vec2 cocNearFar = vec2(texture2D(nearCoCBuffer, uv).r, texture2D(farCoCBuffer, uv).g);
+		cocNearFar = min(cocNearFar * scale, 1.0);
+
+	#endif
 
 	// The far color buffer has been premultiplied with the CoC buffer.
 	vec4 result = inputColor * (1.0 - cocNearFar.y) + colorFar;