diff --git a/WickedEngine/shaders/impostor_prepareCS.hlsl b/WickedEngine/shaders/impostor_prepareCS.hlsl
index 1de3f81a1..47263c5f3 100644
--- a/WickedEngine/shaders/impostor_prepareCS.hlsl
+++ b/WickedEngine/shaders/impostor_prepareCS.hlsl
@@ -31,73 +31,78 @@ void main(uint3 DTid : SV_DispatchThreadID)
 	ShaderMeshInstance instance = load_instance(instanceIndex);
 	ShaderGeometry geometry = load_geometry(instance.geometryOffset);
 
-	[branch]
-	if (geometry.impostorSliceOffset < 0)
-		return;
-
 	float dist = distance(GetCamera().position, instance.center);
-	[branch]
-	if (dist < instance.fadeDistance - instance.radius)
-		return;
+	const bool distance_culled = dist < (instance.fadeDistance - instance.radius);
 
 	// Frustum culling:
 	ShaderSphere sphere;
 	sphere.center = instance.center;
 	sphere.radius = instance.radius;
-	[branch]
-	if (!GetCamera().frustum.intersects(sphere))
-		return;
 
-	uint indexOffset;
-	InterlockedAdd(output_indirect[0].IndexCountPerInstance, 6u, indexOffset);
-	uint impostorOffset = indexOffset / 6u;
-	uint vertexOffset = impostorOffset * 4u;
+	const bool visible = geometry.impostorSliceOffset >= 0 && !distance_culled && GetCamera().frustum.intersects(sphere);
 
-	// Write out indices:
-	output_indices[indexOffset + 0] = vertexOffset + 0;
-	output_indices[indexOffset + 1] = vertexOffset + 1;
-	output_indices[indexOffset + 2] = vertexOffset + 2;
-	output_indices[indexOffset + 3] = vertexOffset + 2;
-	output_indices[indexOffset + 4] = vertexOffset + 1;
-	output_indices[indexOffset + 5] = vertexOffset + 3;
-
-	// We rotate the billboard to face camera, but unlike emitted particles, 
-	//	they don't rotate according to camera rotation, but the camera position relative
-	//	to the impostor (at least for now)
-	float3 origin = instance.center;
-	float3 up = float3(0, 1, 0);
-	float3 face = GetCamera().position - origin;
-	face.y = 0; // only rotate around Y axis!
-	face = normalize(face);
-	float3 right = normalize(cross(face, up));
-
-	// Decide which slice to show according to billboard facing direction:
-	uint slice = uint(geometry.impostorSliceOffset);
-	float angle = acos(dot(face.xz, float2(0, 1))) / PI;
-	if (cross(face, float3(0, 0, 1)).y < 0)
+	// Optimization: reduce to 1 atomic operation per wave
+	const uint waveAppendCount = WaveActiveCountBits(visible);
+	uint waveOffset;
+	if (WaveIsFirstLane() && waveAppendCount > 0)
 	{
-		angle = 2 - angle;
+		InterlockedAdd(output_indirect[0].IndexCountPerInstance, waveAppendCount * 6u, waveOffset);
 	}
-	angle *= 0.5f;
-	angle = saturate(angle - 0.0001);
-	slice += uint(angle * impostorCaptureAngles) * 3;
+	waveOffset = WaveReadLaneFirst(waveOffset);
 
-	const float dither = max(0, instance.fadeDistance - dist) / instance.radius;
-
-	// Write out per impostor data:
-	uint2 data = 0;
-	data.x |= slice & 0xFFFFFF;
-	data.x |= (uint(dither * 255) & 0xFF) << 24u;
-	data.y = instance.color;
-	output_impostor_data.Store2(impostorOffset * sizeof(uint2), data);
-
-	// Write out vertices:
-	for (uint vertexID = 0; vertexID < 4; ++vertexID)
+	[branch]
+	if (visible)
 	{
-		float3 pos = BILLBOARD[vertexID];
-		pos = mul(pos, float3x3(right, up, face));
-		pos *= instance.radius;
-		pos += instance.center;
-		output_vertices_pos_nor.Store4((vertexOffset + vertexID) * sizeof(uint4), uint4(asuint(pos), pack_unitvector(face)));
+		const uint indexOffset = waveOffset + WavePrefixSum(6u);
+		const uint impostorOffset = indexOffset / 6u;
+		const uint vertexOffset = impostorOffset * 4u;
+
+		// Write out indices:
+		output_indices[indexOffset + 0] = vertexOffset + 0;
+		output_indices[indexOffset + 1] = vertexOffset + 1;
+		output_indices[indexOffset + 2] = vertexOffset + 2;
+		output_indices[indexOffset + 3] = vertexOffset + 2;
+		output_indices[indexOffset + 4] = vertexOffset + 1;
+		output_indices[indexOffset + 5] = vertexOffset + 3;
+
+		// We rotate the billboard to face camera, but unlike emitted particles, 
+		//	they don't rotate according to camera rotation, but the camera position relative
+		//	to the impostor (at least for now)
+		float3 origin = instance.center;
+		float3 up = float3(0, 1, 0);
+		float3 face = GetCamera().position - origin;
+		face.y = 0; // only rotate around Y axis!
+		face = normalize(face);
+		float3 right = normalize(cross(face, up));
+
+		// Decide which slice to show according to billboard facing direction:
+		uint slice = uint(geometry.impostorSliceOffset);
+		float angle = acos(dot(face.xz, float2(0, 1))) / PI;
+		if (cross(face, float3(0, 0, 1)).y < 0)
+		{
+			angle = 2 - angle;
+		}
+		angle *= 0.5f;
+		angle = saturate(angle - 0.0001);
+		slice += uint(angle * impostorCaptureAngles) * 3;
+
+		const float dither = max(0, instance.fadeDistance - dist) / instance.radius;
+
+		// Write out per impostor data:
+		uint2 data = 0;
+		data.x |= slice & 0xFFFFFF;
+		data.x |= (uint(dither * 255) & 0xFF) << 24u;
+		data.y = instance.color;
+		output_impostor_data.Store2(impostorOffset * sizeof(uint2), data);
+
+		// Write out vertices:
+		for (uint vertexID = 0; vertexID < 4; ++vertexID)
+		{
+			float3 pos = BILLBOARD[vertexID];
+			pos = mul(pos, float3x3(right, up, face));
+			pos *= instance.radius;
+			pos += instance.center;
+			output_vertices_pos_nor.Store4((vertexOffset + vertexID) * sizeof(uint4), uint4(asuint(pos), pack_unitvector(face)));
+		}
 	}
 }