Can someone explain Doorway to me? What will it do to my Cortex-generated ramps and shapes?
So Doorway is a KeyGenerator+Fader (or thats how I see it in my head).
KeyGenerators are just analogue comparators, that create solid shapes (without gradients) pretty much like a key hole or like a graffiti stencil
Think KeyGenerators as a way to create a hole (or wipe) between two signals. To do this try patching the diamond ramp from your cortex (H+V with mirroring) into the source and you should see a black/white diamond. With the gain control of the KeyGen you can control the size of the key/mask in this example you can control how big the diamond is, the comparator is basically matching the “threshold” value with the gradient of the diamon and then its letting it pass eith with a black (0v) or white(1v). Its very important to understand that KeyGens only produce stencils (0v or 1v) and not gradients.
The next thing will be to patch different signals into the foreground and background inputs of your doorway. Lets say you patch a horizontal range VCO into the background, and a vertical range VCO into the foreground. This will change the key output to a Shape with a diamond filled with horitonzal lines (from the vertical vco), and a background with vertical lines (from the horizontal vco).
So if you input signals into source+background/foreground you have a KeyGen+Fader if you only input signal into the source input you will only have a stencil output (0v or 1v) with a shape that will depend on the source signal and the comparator threshold value.
BTW you also have a keygenerator in the VisualCortex (you need to set the switch to + or - key) and this will wipe between chan A and chan B of the cortex using the shape you input in the key input of the cortex.
There are many ways to use this module.
Electrically, it is a voltage controlled high gain amplifier with clipping and offset, which controls a voltage controlled crossfader. The outline function also turns it a variant on a full wave rectifier.
In video/broadcast terms, it is a key generator and a monochromatic keyer (it has a single channgel crossfader, not an RGB crossfader.) When fed ramps and gradients, this makes it a wipe generator, where the threshold controls the wipe transition like on a video mixer or console. If fed luma video as the source, it is a luma key generator.
In synthesis terms, it is a waveshaper and crossfader. It can change the shape of input waveforms in various ways, and then use those waveforms to crossfade between two sources.
In the system use case, typically you send some waveforms or mixes of them to this, and use it to generate a hard edged shape or key pattern. That pattern can then fade between two other patterns, so it lets you quickly build up complex arrangements. You then either mix those arrangements directly to RGB video (by patching them to color inputs or mixes) or use them as modulation for compositors or colorizer offsets.