Floating point Textures in Compute Shaders

Hi,
I am kind of new to Compute shaders, so I might be missing something basic, hence I apologize in advance if this sounds too noobish.

I am trying to do fluid simulation in 3d. I have implemented the same in 2d using a pixel shader. I passed the x and y values of velocity as the r and g channel of a floating point render texture and the pressure as the b channel and used Graphics.Blit to run the simulation. It all worked fine.

Now I am trying to do the same in 3d but using a ARGBF texture3D to store the x,y and z values of velocity in r,g and b respectively and pressure in a. This is how I initialize them in cs.

Code (CSharp):

1.             FieldT = new RenderTexture(dimension, dimension, 0, RenderTextureFormat.ARGBFloat);
2.             FieldT.volumeDepth = dimension;
3.             FieldT.isVolume = true;
4.             FieldT.enableRandomWrite = true;
5.             FieldT.Create();
6.  
7.             FieldCopyT = new RenderTexture(dimension, dimension, 0, RenderTextureFormat.ARGBFloat);
8.             FieldCopyT.volumeDepth = dimension;
9.             FieldCopyT.isVolume = true;
10.             FieldCopyT.enableRandomWrite = true;
11.             FieldCopyT.Create();
12.  

And in my Compute shader:

Code (CSharp):

1. Texture3D<float4> FieldT;
2. RWTexture3D<float4> FieldCopyT;

Then I use them, for example, as :

Code (CSharp):

1.     float4 FieldCentre = FieldT[id + int3( 0, 0, 0)];
2.     float4 FieldRight  = FieldT[id + int3( 1, 0, 0)];
3.     float4 FieldLeft   = FieldT[id + int3(-1, 0, 0)];
4.     float4 FieldTop    = FieldT[id + int3( 0, 1, 0)];
5.     float4 FieldDown   = FieldT[id + int3( 0,-1, 0)];
6.     float4 FieldRoof   = FieldT[id + int3( 0, 0, 1)];
7.     float4 FieldBase   = FieldT[id + int3( 0, 0,-1)];

And also as :

Code (CSharp):

1.     float3 Was         = UV - dt*FieldStep*FieldCentre.xyz;      
2.     FieldCentre.xyz = FieldT.SampleLevel(_LinearClamp,Was,0).xyz;    

However, unlike in 2D, the Compute shader seems to be ignoring the fact that it is a Floating point texture, as when I run it, I only seem to be getting flow in the positive xyz directions (so I assume it is setting any negative value to zero). Is there a way to make the compute shader treat the texture as signed float or am I missing something very simple?

 

Anyone???