Help needed with ellipses (circles in perspective)!
3yr
Samuel Eli
Hi!
So - I've been grinding away at Marshal Vandruff's 1994 Perspective Series - and there is this one problem I can't seem to solve when doing my own practice.
I believe I'm understanding the concept correctly - that is, getting a circle on a flat vertical plane to be in perspective (2 point). However, once I've got everything drawn up and ready to plot the ellipse, it's clearly distorted or incorrectly placed.
(1) Find the center of the plane by drawing the diagonals, (2) take that center and tracing back to the opposite side's VP, (3) establish major and minor axis at 90 degrees, and (4) do ellipse.
I've watched other artists do this similar method, and when I watch them do it, it all makes sense. But, when the time comes to try something organic from me on my own, it always comes out - distorted and not correct? Anyone out there have any input on this?
First image is me doing it by hand, second is me doing it again in digital (a bit cleaner). Out of perspective, the boxes sides should just be a perfect circle inset on the side plane of the box.
Thanks in advanced!
You need to get an intuition for the cube in perspective first. Like the others mentioned, you're doing some random box - you need a cube first. Or you know a square if we're talking about one face only.
I recommend you use a free 3D app like Blender and experiment with different camera focal lengths because they affect how distorted the perspective is. Draw them free hand as you reference the cube from the 3D app and check to see how far off you are. That's how you get the intuition for it. Good luck!
By the way, just in case it isn't obvious - you can do this exercise with circles inscribed in squares in the 3D app, cylinders and any other 2D and 3D form for that matter.
I don't quite understand but it seems to me that what you want to do is not an ellipse in perspective but a circle in perspective.
So, I'm attaching a little sketch I made in a hurry and it's rather ugly, just to help me with the explanation (I've always had a bad technical stroke, even using a drafting table, let alone a ballpoint pen on a notebook, considering that I'm not used to drawing on paper anymore. I just don't feel like opening photoshop right now! 😅😅)
OK, when you want to draw a figure in space you have to make sure you have as many reference points as possible.
Therefore, as you have rightly guessed, you have to start from a square, in which you will inscribe the circle (a circle whose circumference will have to touch all 4 sides of the square, which is not the case in your drawing), only in your drawing the construction of the square that should guide you is already wrong.
So, first you will draw a square in the plane, inside which you will draw the circle.
Then you will draw the vertical axis, the horizontal axis and the two diagonals.
In this way you will have 8 reference points.
You will draw the vertical points on the line where the observer is positioned (I don't know what it's called in English, basically the horizontal line at the bottom of your perspective plane) and the vertical points by means of 45 degree projections, as you can see in my (ugly) sketch.
In this case we have two points of view: towards one the vertical points will be directed and towards the other the horizontal points.
At the points where they meet you have the 4 corners of the square, which you will use to determine the diagonals and thus find the centre of the square.
Using the centre dividing lines and diagonals, you will then construct your circle in perspective, making sure that the circle touches all 4 sides of the square.
It requires a bit of practice but this is the procedure for 2 point prospective (Keeping in mind that my sketch totally sucks! 🤣🤣🤣)
Thanks for the input!
Yeah, I woke up this morning reviewing the comments and realized the mistake I was making rather quickly.
I wasn't paying enough attention to the true definition of "square" in relation to how a circle is defined. I was thinking that the technique could work for any box, but it has to be a perfect, equally symmetrical square.
I think that was my problem to begin with.
One of the things Scott Robertson talks about in his book is using ellipses to estimate a cube. In other words, draw the ellipses first, get them placed, and then draw the cube around them.
Your ellipses look like they are in correct perspective. They are just too far apart.
Yeah, you are correct. Actually, I know what your talking about with regards to Scott Robertson.
I actually found his steps as rather self evident, but when I was studying other sources, it was in the reverse order. I was getting frustrated as to why I couldn't reverse engineer by going square>ellipse, instead of ellipse>square.
Hi @Samuel Eli, i went through Marshall's perspective course recently as well. The first thing i noticed was that the box you drew is not a cube, the length sides are larger than the height of the box. This means that if you want to draw a perfect circle in one of the side planes the circle will touch the top and bottom of the rectangle, but it will not touch the left and right side of the rectangle. So i think the construction of the ellipse is fine. Try doing it on a more perfect cube in perspective and it will work out better. In the beginning of Marshall's classes he eye-balled/estimated a perfect square in perspective, in the last class he actually provides a method to draw perfect squares in perspective (Planned Projection). Hope this helps
It does, I see the problem now. A little frustrated with myself in how I didn't pay attention to that particular detail >.>
Is it just that the box isn't a cube in your example? If you are trying to make the circles fill the box face, it will be distorted (a flattened cylinder) if the box is rectangular. If this is the issue, then just look up drawing a cube in perspective to see how to make sure the surface is equal within the perspective lines.
