I was wondering if anyone knew how I would go about making or obtaining a shader to be the glass part of a magnifying glass so that it will magnify what is seen on the other side.
well… i'm not a very specialist of Houdini but as I know from other software it is enough to use glass shader and change index of refraction to some higher value. Double sided surface is also good idea. (of course lenses should be sphered to give rays chance to brake on it diffrently…)
Another idea (depending on type of shot) is to make this effect in compositing. As you expect it is much faster. Just render your object (lens) as a matte, track it in compositon, add a gradient color from a center to edges and use it as a mask for distortion of original render object.