Idea about Feature extraction

I am currently working on a system that extracts certain features out of 3D-objects (Voxelgrids to be precise), and i would like to compare those features to automatically made features when it comes to performance (classification) in a tensorflow cNN with some other data, but that is not the point here, just for background. My idea now was, to take a dataset (modelnet10), train a tensorflow cNN to classify them, and then use what it learned there on my dataset – not to classify, but to extract features.

So i want to throw away everything the cnn does,except for what it takes from the objects.

Is there anyway to get these features? and how do i do that? i certainly have no idea.

any ideas would be greatly appreciated.