If you like the Doepfer Morph Controller, you can achieve the same behavior and more with the Toppobrillo Mixiplexer:
Essentially, if you put a DC offset into the All In input, turning the Position knob will output the same shapes that you see on the Doepfer.
It’s more interesting to me because you can also take four inputs and morph them down to one output, or take four inputs and selectively switch between which one is active.
Intellijel Planar is another great choice. Again, you can send in an offset and then have useful shapes on the four quadrant outputs. Alternatively, you can again take four inputs and morph through them for one output.
I’ve tackled a few of these ideas in my Euro Reakt for Reaktor package (https://www.native-instruments.com/en/reaktor-community/reaktor-user-library/entry/show/9093/):
The 8-Way Scanner is like an eight channel version of the Mixiplexer. For the 8 individual outputs, you can choose between OUTS and AMPS mode. AMPS outputs a CV based on how “open” that channel currently is (basically, the CV used to open the VCA on that channel).
The Meta Control is a single knob that controls the level of four outputs. We put this is the Unfiltered Audio products as well. There are two modes: INT and EXT. In INT mode, the MAIN knob generates a DC offset that is sent to the four outputs. The level of each output is controlled by the associated attenuverter. The easiest point of comparison are the Macro knobs on something like Native Instruments’ Massive, where one knob controls multiple parameters. In EXT mode, the MAIN knob acts as an attenuverter for the signal present at Ext. In. So, same idea, but this time you can avoid having static outputs.
Vector Mix is more like the Planar. It has four inputs arranged in quadrants. The Mix output is determined by the X and Y controls. Simultaneously, you can see that there are both regular outputs (the input multiplied by that quadrant’s VCA) and CV outputs (the VCA’s CV for that output). So, two knobs to rule them all, unless you count a joystick as one =)
These are all open-source, so feel free to open them up and see how any of the algorithms work. The Scanner algorithm was an implementation of some Reaktor 5 standard library code. I’m forgetting which instrument is was, exactly.