Drill 07A cylinder in perspective

How to draw a cylinder in perspective

Draw a cylinder at any angle. Both end ellipses get checked against the axis of the form, and you find out in degrees whether they sit square to it — and whether the far end opens up the way it has to.

Measures whether your ends sit on the formRuns on your deviceFree and unlimitedWant a real drawing checked?

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Draw a cylinder: an ellipse at each end, and a straight side joining them.

Any angle you like. Go big — a small cylinder cannot be measured. Draw the ends as closed ellipses.

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How it works

What it can name

The faults, drawn

A percentage on its own tells you nothing you did not already know. These are the separable problems the measurement identifies — each with a different fix, which is the whole reason for telling them apart. Every example below is a real stroke, generated by the same code that tests the engine.

  • Ends off square

    The one this exercise exists for. The short way across an end ellipse runs along the axis of the form — not upright, not square to the page. An ellipse drawn on its own always looks fine, which is why this survives until the form is finished and then reads as bent.

  • Far end drawn narrower

    The instinct, and it is backwards. The far end is smaller on the page, so it feels as though it should be squashed too. Its degree opens as it recedes; drawn the other way it describes a cone.

  • Both ends the same degree

    The second ellipse copied from the first rather than drawn for where it sits. Without a shift between them there is no depth in the form and it reads as a flat tube.

  • Sides that miss the ends

    Drawn between the ellipses rather than onto them. A silhouette line leaves the widest point of one end and arrives at the widest point of the other, and those points are not where the eye first looks.

  • No taper

    Sides run as parallel rails, which is what a cylinder looks like flat on the page and never what one looks like in space. Anything going away from you gets narrower.

  • Bowed silhouette

    Drawn from the wrist, or drawn slowly enough to steer. The silhouette of a cylinder is straight, and a confident line that misses beats a careful one that wanders.

Two tools, two questions

What this drill looks at

This drill · your line

Measures the two things a cylinder is judged on — whether each end ellipse is square to the axis, and whether the far end is drawn wider than the near one.

The number is arithmetic. The finding is not: which fault a set of measurements adds up to, and which fix it takes, is how drawing has been taught for a century. The instrument locates it; the teaching names it.

  • Instant, exact, and the same answer every time
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  • Cannot tell you whether the drawing works

Rate My Sketch · your drawing

Coach Luna checks a real drawing — a photo of your sketchbook or a screenshot — and marks the corrections onto the image itself.

She measures technique against what you were drawing: proportion versus your reference, shading, the joins. Never your creativity, your style or your subject — those are not hers to grade.

  • Five technique scores, and the single fix to make first
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Have your drawing checked

The two scores are different measurements and are not meant to agree. A circle can be geometrically excellent inside a drawing that does not work, and a drawing can work with shaky circles all through it. Use the drills to build the hand, use the critique to find out what the drawing needs next, and when you want the rest taught properly — construction, form, light, composition — that is what the Sketching Essentials course is for.

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How the number is made

What the score actually measures

Squareness

angle between each end’s minor axis and the axis of the form31% of the score

The whole exercise. The short way across an end ellipse has to run along the axis of the cylinder, wherever that axis points. Under about four degrees is a genuinely well-placed end.

Recession

how open the far end is − how open the near end is20% of the score

Whether the far end opens up. "How open" is measured as an angle: a circle seen square on is 90°, and one seen edge-on is 0°. The far end should be several degrees more open than the near one — equal ends read as a flat tube, and a far end that is less open reads as a cone.

End shape

first and fourth harmonics of each end’s radial error8% of the score

Whether each end is actually an ellipse. Everything else here reads an end’s angle or how open it is, and both can be exactly right on a shape that is not an ellipse at all — a half that runs into the body and comes out shallower than the half outside it, or long ends that come to a point instead of a curve. This is safe to state rather than guess at, because the perspective projection of a circle is exactly an ellipse and an ellipse is exactly symmetric about both its axes: no viewpoint makes one half legitimately shallower or one tip legitimately sharper.

Joins

gap between each side and the widest point of each end ÷ end radius17% of the score

Whether the sides actually meet the ends. A silhouette line has to graze both ellipses, and until it does this is two ellipses with two lines near them.

Taper

(near width − far width) ÷ near width13% of the score

How much the form narrows as it goes away. Sides that stay parallel describe a cylinder seen flat on the page rather than one in space.

Linework

furthest deviation from straight ÷ side length, worse of the two sides11% of the score

How much each side wanders. Measured on the same scale as the straight-line drill, because a bowed silhouette and a badly placed one need opposite fixes.

Weighted toward squareness and recession, because those are the two things that make a drawn cylinder read as a solid — the rest describe how tidily it was assembled. Every threshold, and the evidence behind it.

The technique

Draw a cylinder in perspective

  1. 01

    Draw the axis first

    One stroke, all the way through, before either end. Everything else is measured against this line, so it is the one decision worth making deliberately.

  2. 02

    Put the near end on it

    The narrow direction of the ellipse lies ON the axis; the wide direction is square across it. Ghost it a few times checking that before you commit.

  3. 03

    Open the far end up

    Smaller across than the near one, and MORE open — a little closer to a circle. This is the step almost everybody does backwards.

  4. 04

    Join the widest points

    Mark the two points on each ellipse furthest across the axis. Each side runs from one to its match, grazing both.

Why the ends are the hard part

A cylinder is two ellipses and two lines, which sounds like the easiest form there is. It is not, and the reason is that an ellipse drawn on its own always looks fine. Nothing about it is wrong until it is attached to a form, and then the whole thing reads as bent without anybody being able to say which part is at fault.

The rule is that the short way across each end ellipse — its minor axis — runs along the axis of the cylinder. Not upright, not square to the page: along the axis, wherever the axis happens to point. The moment the form is drawn at an angle, the ellipse everybody instinctively draws is the one that is square to the page, and it is wrong by exactly the angle the cylinder is tilted at.

It is a single number, it is exact arithmetic, and it is invisible from the inside. That combination is the entire argument for measuring it rather than squinting at it.

The far end gets wider, not narrower

This is the one people get backwards, and it is worth being blunt about why. The far end of a cylinder is smaller on the page — everybody knows that, and it is true. The instinct that follows is that it should be narrower in every sense, so the ellipse gets squashed as well as shrunk.

In fact it OPENS UP as it goes away from you. Draughtsmen call this the ellipse’s degree, and it is just an angle: a circle seen square on is 90°, one seen edge-on is 0°, and every ellipse in between is somewhere on that scale. Carry the cylinder on far enough and its ends keep opening until one becomes a full circle. That is the direction they travel, and a cylinder whose two ends sit at the same angle has no depth in it at all.

Exaggerate it at first. In several thousand years of people drawing cylinders, almost nobody has overdone this one.

What this has to do with boxes

The box drill asks whether your straight edges agree about where they are going. This asks the same question of your curves, and it is the exercise that follows boxes in every curriculum that teaches boxes at all — Drawabox puts 250 cylinders directly after its 250 boxes for exactly this reason.

The two are the same skill seen from opposite sides. A box is easy to check with a ruler and hard to draw; a cylinder is easy to draw and, until now, almost impossible to check, because the thing that is wrong with it is an angle between an ellipse and a line that nobody has drawn.

When you have got it

Both ends inside four degrees of square, with the far end at least a few degrees more open than the near one, on a cylinder you drew at an angle you did not choose in advance.

Questions

Which way should the ellipse point?

The narrow direction of each end ellipse runs along the axis of the cylinder. If the cylinder is tilted, the ellipse is tilted the same amount — the ellipse that looks square to the page is wrong by exactly the tilt of the form.

Why is my far ellipse supposed to be wider?

Because it opens up as it recedes, even though the ellipse itself is smaller on the page. Both are true at once: smaller across, more open. "Open" here is an angle — a circle seen square on is 90°, one seen edge-on is 0° — and two ends at the same angle read as a flat tube rather than as a form going away from you.

Does it matter which end I draw first?

No. The strokes are sorted by shape rather than by the order they arrived, so you can draw both ends and then the sides, or work around the form, and it is read the same either way.

Do I need a tablet for this?

No. It works with a mouse or a finger, and the measurement scales to your input device so a phone is not scored more harshly than a desktop.

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These drills measure geometry. For a drawing with a subject in it, Luna scores five technique dimensions and marks the corrections on your image.