The phenomena experienced on DMT are illusory. The world we preceptive isn't actually the world our eyes view. Our visual perception of reality is the product of how our brain interprets the data from our eyes and other senses. This process is evident where artist exploit this in optical illusions.
Known as the Pac-Man illusion, this is an example of afterimage complementary color (green as opposite to lilac). Follow the movement of the rotating pink dot with your eyes and the dots will remain only one color, pink. But if you stare at the black + in the center, the moving dot will turn green. (by Jeremy L. Hinton)
Surface color of both A and B parts is identical. Just use a finger to cover the place where both parts meet and you'll see.
This image is stationary.
Another example is the visual blind spot. Our visual system actually has large blind spots. Our brains compile data and fill in the blanks.
Other variables such as opinion, mood, smell, taste, age, and what not influence the composite we perceive as our visual reality. DMT disrupts this process and as our brain attempts organizing sensory input we perceive an extremely distorted reality. Often our hallucinations have foundations in the stimuli we were processing earlier. If you were eating or drinking earlier perhaps the hallucinations could have an oral focus. If you were thinking of humans earlier perhaps your brains attempts at organizing the disrupted stimuli could result in the illusion of humanoid beings. Your experience could even get influenced by something your read.