Convert a object into it's mirror image?

Hello, I’m pretty much a n00b to blender and 3D modeling, but I am learning, I was wondering, is there a quick way to take a asymetrical object you are working on like a random blob, and tell blender to turn it into it’s own mirror image and keep working on it? All the mirror functions I’ve found on the interface don’t do that, the mirror modifier makes a mirror image and basically “welds” it to the orginal, I just want to take the object and turn it into it’s mirror image, any help is much appreciated.

you could use a mirror modifier, apply it and then remove the original vertices

Simple - scale it to -1 of the original, using S. If you want to mirror it in a particular plane, make sure you constrain the scale to that plane by hitting x, y or z. So S -> x/y/z -> -1 -> Enter.

Yeah, what indigomonkey said. Or, you could select it and hit “CTRL+M”.

If you want to work both copies at once then the mirror modifier will do it. Just move the original sideways in Edit mode so each copy sits either side of the centre point (or move the object centre to one side in object mode). When you’re done, just select all vertices on one copy, press P to separate them and you now have two separate objects which are mirror images.

Select each one in Object Mode and reset their centres using the “Centre New” button.

I use this method to create eyes, separate-mesh eyelids and detached hands for characters.