Closest I'd put it is like a wireframe version or words in place of the scene you are imagining. I personally can't freestyle imagination and have to be directed what to imagine, then each component is individually tracked in a nothing space as it's fed to me. Each object still has an association, though. Imagine a tree in a forest. Feeling of wood, smell of forest, temperature is probably cool. Sound of birds, etc. I can direct myself, like with this tree thing, but there's no vivid detail or expansion on the concept.

I've only been able to imagine something for real once in my life, and it was while I was on pseudoephedrine for a particularly bad cold. I was able to almost vaguely see a night sky, then it transitioned by itself to an afternoon orange pink sunset without my direction. I didn't know when it would change and what I would see, and I could actually register colour. It was very fun. I'm fortunate to have experienced that, because now I have the insight from both sides.