One Point Perspective Distorted Grid

[johnatthecastle]

In the one-point perspective grid, the grid squares seem distorted. Instead of looking like squares in perspective, they look like rectangles, longer in the direction of the perspective lines. If anything, the perspective should be making them contract in that direction, not stretch. As a test, I tried creating a perfect square and then attaching it to a plane. Sure enough, it no longer looked square, but stretched. Is there a way to correct this?

[Jeff Witchel, ACI]

Can you post a screenshot?

The grid squares look perfect to me.

[Jeff Witchel, ACI]

I get the feeling that the "distortion" your referring to is actually the foreshortening you would expect in a perspective drawing.

[johnatthecastle]

Here is a screenshot. Foreshortening would cause B to be shorter than A, but in this case it is longer.

[Jeff Witchel]

I believe that what you're looking at IS foreshortening. Sure foreshortening happens on the grid as you go back in space. But it also happens as you move up or down from the horizon line AND to the left and right of the vanishing point.

Using the Perspective Grid tool (Shift+P), click on the node at the bottom of the left side grid and move the grid in toward the center and back out and you'll see the grid lines are more square as you move inwards until they become elongated as you get closer to the center. Now click on the nodes to the left or right of the horizon line and drag up and down. You'll notice as the horizon line moves up, the bottom grid rectangles look more square.

Foreshortening becomes exaggerated as you look further away from your point of view.

[johnatthecastle]

That's not how foreshortening works. The plane that's angled away from the viewer (here represented by line B) should always be shorter than the plane facing the viewer (represented by line A), no matter how far from the vanishing point it is. For example. if you were to hold up a cube with one plane facing you, then while staring forward, move the cube to one side without changing its orientation, no matter how far you moved it, the apparent width of the plane facing to the side would never be greater than the apparent height of the plane originally facing directly towards you. Granted that linear perspective isn't perfect in even the best cases, and breaks down at extreme angles, but I'm not working with extreme angles.

So I guess the answer is that this is merely a shortcoming of Illustrator's perspective system that I'll have to work around. Thank you for addressing my question though.

[rcraighead]

This is correct for one-point perspective. There will always be distortion when only one vanishing point is used. In "reality" closer elements would start to "bend", but one-point perspective prevents that, so they are stretched. That's my "perspective" anyway.

[Jacob Bugge]

John,

It may sound too far out, but what happens if you try toggling between GPU and CPU with Ctrl/Cmd+E?

[Ray Yorkshire · Accepted solution]

That type of distortion just happens its not a shortcoming of Illustrator.

Here is a video showing the same on an art program, Clip Studio Paint .

One Point Perspective - Perspective Drawing - YouTube

Subtitles available..

[mpronto]

Foreshortening in perspective causes the dimension to become "less" not extended.
Perspective doesn't turn a cube into a coffin! It gets "shorter" (ie foreshortening).
The 1 point perspective grid is out to lunch. Completely.

[Doug A Roberts]

Can you demonstrate one-point perspective that doesn't do what Ray's example does?