diff --git a/src/mol-canvas3d/canvas3d.ts b/src/mol-canvas3d/canvas3d.ts
index 96483552515c7f4a5c8856c28d159a319e420542..f1a359800c76e52de778cc24e4755f6dfcf5b424 100644
--- a/src/mol-canvas3d/canvas3d.ts
+++ b/src/mol-canvas3d/canvas3d.ts
@@ -425,7 +425,7 @@ namespace Canvas3D {
                     }
                     if (props.postprocessing.occlusionKernelSize !== undefined) {
                         p.postprocessing.occlusionKernelSize = props.postprocessing.occlusionKernelSize
-                        ValueCell.update(postprocessing.values.uOcclusionKernelSize, props.postprocessing.occlusionKernelSize)
+                        ValueCell.update(postprocessing.values.dOcclusionKernelSize, props.postprocessing.occlusionKernelSize)
                     }
                     if (props.postprocessing.occlusionBias !== undefined) {
                         p.postprocessing.occlusionBias = props.postprocessing.occlusionBias
diff --git a/src/mol-canvas3d/helper/postprocessing.ts b/src/mol-canvas3d/helper/postprocessing.ts
index d917394514f22048ddc715683529f8ab453373c1..e47c803b8e3e1167bf5f8d6da1370ba3d0aeeeaa 100644
--- a/src/mol-canvas3d/helper/postprocessing.ts
+++ b/src/mol-canvas3d/helper/postprocessing.ts
@@ -22,7 +22,7 @@ const PostprocessingSchema = {
     uTexSize: UniformSpec('v2'),
 
     dOcclusionEnable: DefineSpec('boolean'),
-    uOcclusionKernelSize: UniformSpec('i'),
+    dOcclusionKernelSize: DefineSpec('number'),
     uOcclusionBias: UniformSpec('f'),
     uOcclusionRadius: UniformSpec('f'),
 
@@ -52,7 +52,7 @@ export function getPostprocessingRenderable(ctx: WebGLContext, colorTexture: Tex
         uTexSize: ValueCell.create(Vec2.create(colorTexture.width, colorTexture.height)),
 
         dOcclusionEnable: ValueCell.create(p.occlusionEnable),
-        uOcclusionKernelSize: ValueCell.create(p.occlusionKernelSize),
+        dOcclusionKernelSize: ValueCell.create(p.occlusionKernelSize),
         uOcclusionBias: ValueCell.create(p.occlusionBias),
         uOcclusionRadius: ValueCell.create(p.occlusionRadius),
 
diff --git a/src/mol-gl/shader/postprocessing.frag b/src/mol-gl/shader/postprocessing.frag
index e6da74a2f0fb77a5a24d3bf29d3f031dc623566a..7b73d5b70a7b115d7539d57b79e645ec82679cb0 100644
--- a/src/mol-gl/shader/postprocessing.frag
+++ b/src/mol-gl/shader/postprocessing.frag
@@ -6,7 +6,6 @@ uniform sampler2D tColor;
 uniform sampler2D tDepth;
 uniform vec2 uTexSize;
 
-uniform int uOcclusionKernelSize;
 uniform float uOcclusionBias;
 uniform float uOcclusionRadius;
 
@@ -28,16 +27,16 @@ float noise(vec2 coords) {
 float calcSSAO(in vec2 coords, in float depth) {
 	float occlusionFactor = 0.0;
 
-	for (int i = -uOcclusionKernelSize; i <= uOcclusionKernelSize; i++) {
-		for (int j = -uOcclusionKernelSize; j <= uOcclusionKernelSize; j++) {
-			vec2 coordsDelta = coords + uOcclusionRadius / float(uOcclusionKernelSize) * vec2(float(i) / uTexSize.x, float(j) / uTexSize.y);
+	for (int i = -dOcclusionKernelSize; i <= dOcclusionKernelSize; i++) {
+		for (int j = -dOcclusionKernelSize; j <= dOcclusionKernelSize; j++) {
+			vec2 coordsDelta = coords + uOcclusionRadius / float(dOcclusionKernelSize) * vec2(float(i) / uTexSize.x, float(j) / uTexSize.y);
             coordsDelta += noiseAmount * (noise(coordsDelta) - 0.5) / uTexSize;
             coordsDelta = clamp(coordsDelta, 0.5 / uTexSize, 1.0 - 1.0 / uTexSize);
 			if (texture2D(tDepth, coordsDelta).r < depth) occlusionFactor += 1.0;
 		}
 	}
 
-	return occlusionFactor / float((2 * uOcclusionKernelSize + 1) * (2 * uOcclusionKernelSize + 1));
+	return occlusionFactor / float((2 * dOcclusionKernelSize + 1) * (2 * dOcclusionKernelSize + 1));
 }
 
 float calcEdgeDepth(in vec2 coords) {
@@ -63,10 +62,10 @@ float calcEdgeDepth(in vec2 coords) {
 
 void main(void) {
 	vec2 coords = gl_FragCoord.xy / uTexSize;
-	vec4 color = texture(tColor, coords);
+	vec4 color = texture2D(tColor, coords);
 
 	#ifdef dOcclusionEnable
-		float depth = texture(tDepth, coords).r;
+		float depth = texture2D(tDepth, coords).r;
 		if (depth != 1.0) {
 			float occlusionFactor = calcSSAO(coords, depth);
 			color = mix(color, vec4(0.0, 0.0, 0.0, 1.0), uOcclusionBias * occlusionFactor);