stage3d textures pixel info readback in flash

Ls,

Perhaps a bit specific, but I couldnt find a stage3d forum. If there is please direct me to it.

Im trying to  use/abuse the GPU for some heavy calculations.

I can create a vertex shader to manipulate the vertices of a mesh containing the xyz's that I need

But I dont know how to read back the changes made by the vertex program to the vertex coordinates.

So Im not making translations in flash and feeding them to stage3d, but i want to do it the other way around.

I thought about combining it with a fragment shader to put the xyz vertices coords as rgb pixels in a texture.

But then, how to read the texture in flash?

I could perhaps do a stage3d createbitmap, but I hear thats very slow.

Could I access the backbuffer directly?

I only need about 100 pixels for info storage so a 10x10 stage/texture would suffice.

Thx for reading this far.

Regards,

M