critical fix with particle sorting unsigned counter underflow

WickedEngine/emittedparticle_kickoffSortCS.hlsl

@@ -14,7 +14,7 @@ void main( uint3 DTid : SV_DispatchThreadID )
 	counterBuffer[0].aliveCount_afterSimulation = aliveCount_afterSimulation;
 
 	// calculate threadcount:
-	uint threadCount = ((aliveCount_afterSimulation - 1) >> 9) + 1;
+	uint threadCount = ((max(1, aliveCount_afterSimulation) - 1) >> 9) + 1;
 
 	// and prepare to dispatch the sort for the alive simulated particles:
 	indirectBuffers.Store3(ARGUMENTBUFFER_OFFSET_DISPATCHSORT, uint3(threadCount, 1, 1));

WickedEngine/wiEmittedParticle.cpp

@@ -212,6 +212,7 @@ void wiEmittedParticle::CreateSelfBuffers()
 	counters.aliveCount = 0;
 	counters.deadCount = MAX_PARTICLES;
 	counters.realEmitCount = 0;
+	counters.aliveCount_afterSimulation = 0;
 
 	data.pSysMem = &counters;
 	bd.ByteWidth = sizeof(counters);
@@ -394,7 +395,10 @@ void wiEmittedParticle::UpdateRenderData(GRAPHICSTHREAD threadID)
 
 		unsigned int numThreadGroups = ((MAX_PARTICLES - 1) >> 9) + 1;
 
-		if (numThreadGroups>1) bDone = false;
+		if (numThreadGroups > 1)
+		{
+			bDone = false;
+		}
 
 		// sort all buffers of size 512 (and presort bigger ones)
 		device->BindComputePSO(&CPSO_sort, threadID);