Write to additional texture in ShaderMaterial shader

Is it possible to render to an additional, off-screen texture in a shader used in a ShaderMaterial?
I’m doing some point-picking on a pointcloud, and currently, I’m doing two totally separate passes. The first pass does the normal pointcloud rendering (to screen), while the second pass renders some additional information into an offscreen texture.

I’d like to combine this process, so that the shader that writes to the camera color buffer also writes to the offscreen texture (for performance, and it just makes more sense). I know there’s a “MultiRenderTarget” feature, but I couldn’t figure out how to use it when one of the render targets is the screen/camera.

@sebavan, @Deltakosh

You can only do it with MultiRenderTarget but nothing can render on screen during this pass.