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When using a 2 point perspective system, it is always advisable to place the vanishing points outside of the composition, so the shapes do no look forced and distorted. If the angle of the object is quite severe, though, one of the vanishing points could fall inside the composition.

Consider the following case. I drew first Cube 1 placing the RVP is inside the composition on purpose. Cube 1 looks great. Then I tried to move Cube 1 to the right of the RVP, just dragging along the X axis, keeping it parallel to its original position, which would be Cube 2. It looks distorted, though. Cube 2 is parallel with Cube 1 so the parallel edges on both cubes are supposed to vanish to the same point. It does not work, though. The reason for this is that Cube 2 is to the right or the RVP.

I know I can solve this problem with extra vanishing points, but then it would not be a 2 vanishing point system anymore. I could also move the viewer to the right, but then the vanishing points would change. I am trying to understand why it does not work as it is.

enter image description here

So, questions:

  • In a 2 vanishing point system, does everything need to be placed between the vanishing points to avoid these aberrations (i.e. nothing to the left of the LVP or to the right of the RVP)? Is this a limitation of the system itself?
  • Would Cube 2 be outside of the Cone of Vision in this case? Is that the reason why it looks distorted?
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Distortion happens. :) Escher made a career out of playing with the natural distortion which happens in perspective.

Based on question title -- No. Based on question in your post --- Yes (they are opposite questions :) )

For a natural appearance in 2 point perspective all items must fall between the 2 vanishing points. Any object which falls outside either of the two vanishing points will be distorted and appear unnatural using strictly 2-point perspective.

For things at the edge of the viewport there is natural distortion. Once you pass a vanishing point, you are passing what the natural field of vision would be -- essentially creating an image that a human could not perceive in real life - so objects outside the vanishing points will always appear odd since we never see such objects in nature.

Once an object passes either horizontal vanishing point it's imperative to use 3-point perspective, not 2 point. By using only 2-point perspective you are distorting the horizontals but none of the verticals. Human vision is curved and verticals must be also distorted to maintain a more natural perspective view.

When you add a proper 3rd vanishing point the cubes appear more natural:

enter image description here

So, in short, 2-point perspective only works when all object fall between the two vanishing points. Once any object passes a vanishing point you must switch to 3-point perspective in order to represent natural vision distortions.

NOTE: Isometric Projection is founded on 2-point perspective while appearing like 3-point perspective and diminishing the distortion of objects across the viewing range. It's not real perspective in the same sense as 2-point or 3-point perspective, but does a great job of conveying depth without distortion.

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I think the answer to your 1st question is "yes." As the viewer rotates, any arbitrary vanishing point is going to be a line from the center of the view to the horizon.

This isn't a limitation, but rather a mere fact of reality.

n-point perspective is always going to look synthetic. Artistically, playing with this in the manner you illustrate might give rise to interesting compositions.

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