#pragma kernel CSMain
#define NUM_THREADS 8

float4 _Size, _Up;
float _AmbientTemperature, _DeltaTime, _Buoyancy, _Weight;

RWStructuredBuffer<float3> _Write;
StructuredBuffer<float3> _Velocity;
StructuredBuffer<float> _Density, _Temperature;

[numthreads(NUM_THREADS,NUM_THREADS,NUM_THREADS)]
void CSMain (int3 id : SV_DispatchThreadID)
{

    int idx = id.x + id.y*_Size.x + id.z*_Size.x*_Size.y;
    
    float T = _Temperature[idx];
    float D = _Density[idx];
    float3 V = _Velocity[idx];
    
    if(T > _AmbientTemperature)
    	V += (_DeltaTime * (T - _AmbientTemperature) * _Buoyancy - D * _Weight) * _Up.xyz;
    
    _Write[idx] = V;
}