Is it possible to transfer mesh to VRAM without rendering it?

You could use DirectX 11 buffers which Unity 4 gladly supports. Something like this pseudocode:

     public Material MyMaterial;
     protected ComputeBuffer sourceBuffer;
 
     protected void Start() {
         sourceBuffer = new ComputeBuffer(<number of verteces>, <vertex size in bytes>, ComputeBufferType.Append);
         sourceBuffer.SetData(<array with mesh data>);
     }
 
     protected void OnRenderObject() {
         MyMaterial.SetPass(0);
         MyMaterial.SetBuffer("pointBuffer", sourceBuffer);
         MyMaterial.SetMatrix("MVP", Camera.main.projectionMatrix*Camera.main.worldToCameraMatrix*transform.localToWorldMatrix);
         Graphics.DrawProcedural(MeshTopology.Points, ParticlesCount);
     }
 
     protected void OnDisable() {
         sourceBuffer.release();
     }

With shader which looks like this:

     #pragma target 5.0
 
     struct Vertex
     {
         float4 position;
         float4 normal;
     };
 
     float4x4 MVP;
     StructuredBuffer<Vertex> pointBuffer;
 
     vs_out vert (uint id : SV_VertexID)
     {
         vs_out o;
         float4 p = pointBuffer[id].position;
         ...
         return o;
     }

Refer to Unity 4 manual on buffers.

just a quick question with this:

i am using unity 4, and have a shadermodel 5 card.

but when i try the above idea, i get an error at vs_out vert (uint id : SV_VertexID)

it says that sv_vertexID is basically not recognized.

any idea how to get access to the vertexID?

is it only available in shadermodel 5?