/ic/ - Artwork/Critique

>>1788668
Well, you can't really apply the cone of vision freehand properly, nor it it necessary in most cases. All you really need is that both of your vanishing points can't be on the same page and whatever you draw on the page should look fine, except maybe the distant corners of the page.

I whipped up a quick diagram that should be the same as in Robertson's book. Setting the horizon and a vertical line that goes from the center vanishing point down to the station point, you can then place your two vanishing points for 2 pt perspective anywhere on the horizon as long as the two points meet at the station point at a 90 degree angle. With that in mind, if you were to start from a drawing or photo, you could find the horizon and two vanishing points and use those to find the station point.

The cone if vision (or the circle at the base of it) is found by taking lines from the station point to the horizon that are each 30 degrees from the center line (the two add up to 60 degrees). Anything in that circle should look normal, but get progressively more distorted by perspective the further you get from the center. You can't go beyond red circle without getting more noticeable distortion. The blue box that surrounds the red circle represents your picture plane. Your entire picture that you want to show should be contained within that box, but you can crop that box down further as needed.

Again, you can technically go beyond that box, as the only consequence is more distortion from perspective. Get too distorted and it would appear natural anymore. If you had a wide angle lens, then the green lines in the diagram would be at a wider angle than the 30 degrees shown. The result is a larger circle, and thus a larger box for the picture plane, and finally in turn more distortion from perspective in your canvas.


tldr; The cone of vision defines the edges of your usable canvas to avoid unnatural looking distortion due to perspective