diff --git a/orx-fx/src/commonMain/kotlin/Post.kt b/orx-fx/src/commonMain/kotlin/Post.kt
index 6be90250..8b1a7744 100644
--- a/orx-fx/src/commonMain/kotlin/Post.kt
+++ b/orx-fx/src/commonMain/kotlin/Post.kt
@@ -2,6 +2,7 @@ package org.openrndr.extra.fx
 
 import org.openrndr.Extension
 import org.openrndr.Program
+import org.openrndr.color.ColorRGBa
 import org.openrndr.draw.*
 
 class Post : Extension {
@@ -25,6 +26,11 @@ class Post : Extension {
      */
     var inputType = ColorType.UINT8
 
+    /**
+     * The depth format to use for the input buffer
+     */
+    var inputDepthFormat = DepthFormat.DEPTH_STENCIL
+
     private var output: ColorBuffer? = null
     private var postFunction = { input: ColorBuffer, output: ColorBuffer -> input.copyTo(output) }
 
@@ -77,6 +83,7 @@ class Post : Extension {
             // create new targets and buffers
             inputTarget = renderTarget(art.width, art.height, art.contentScale, multisample = art.multisample) {
                 colorBuffer(type = inputType)
+                depthBuffer(format = inputDepthFormat)
             }
             if (art.multisample != BufferMultisample.Disabled) {
                 resolved = colorBuffer(art.width, art.height, art.contentScale)
@@ -85,6 +92,7 @@ class Post : Extension {
         }
         // bind input target, the next extensions will draw into it
         inputTarget!!.bind()
+        drawer.clear(ColorRGBa.TRANSPARENT)
     }
 
     override fun afterDraw(drawer: Drawer, program: Program) {
diff --git a/orx-fx/src/demo/kotlin/DemoPost01.kt b/orx-fx/src/demo/kotlin/DemoPost01.kt
index f6157802..95109150 100644
--- a/orx-fx/src/demo/kotlin/DemoPost01.kt
+++ b/orx-fx/src/demo/kotlin/DemoPost01.kt
@@ -3,6 +3,8 @@ import org.openrndr.application
 import org.openrndr.extra.fx.Post
 import org.openrndr.extra.fx.blend.Add
 import org.openrndr.extra.fx.blur.ApproximateGaussianBlur
+import org.openrndr.shape.Circle
+import kotlin.math.cos
 
 fun main() = application {
     configure {
@@ -14,7 +16,7 @@ fun main() = application {
             val add = Add()
             post { input, output ->
                 blur.window = 50
-                blur.sigma = 50.0
+                blur.sigma = 50.0 * (cos(seconds) * 0.5 + 0.5)
                 blur.apply(input, intermediate[0])
                 add.apply(arrayOf(input, intermediate[0]), output)
             }