inline float SampleDensity(float3 pos, float scale, float phase)
{
    float bias = 10000;
    float3 texScale  = _VolumeTex_ST.xyx / bias / scale;
    float3 texOffset = (_TexOffset + _ScrollOffset) * phase * texScale;
    float3 texPos    =  pos * texScale + texOffset;

	//radial mask

	//needs...
	//float4 _RadiusOffset;
	//float _RadiusMaskHeight;
	//at the top of this class.

	//and those properties to be exposed in MassiveCloudsMaterial.shader
	//_RadiusOffset("RadiusOffset", Vector) = (0,0,0,0)
	//_RadiusMaskHeight("RadiusMaskHeight", Float) = 0

	float2 posxz = (float2(pos.x, pos.z));
	float2 radiusOffset = (float2(_RadiusOffset.x, _RadiusOffset.y));
	float distFromCenter = distance(((posxz / (pos.y * _RadiusMaskHeight)) + radiusOffset), float2(0, 0));
	float saturated = saturate((distFromCenter + _RadiusOffset.z) * _RadiusOffset.w);
	float3 densityRadialMask = (saturated).xxx;
	//end radial mask.  Multiply density by this!

	return tex3Dlod(_VolumeTex, float4(texPos.xyz, 0)).a * densityRadialMask; // *(1.0 - densityRadialMask);
}