Assignment - Perfect Cubes From Your Mind's Eye
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Assignment - Perfect Cubes From Your Mind's Eye
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Maxime Scheder
There is still a way up to a100 perfect cubes, but I'll do more as warm-up in the future ! Now that I took the picture, I see that some of them aren't exact cubes though. The thing that has always got me with perspective is this chicken-egg conundrum of the ellipse. We need a perfect square to get a perfect circle, but we use ellipses to make perfect cubes... Some day I'll crack the code.
LESSON NOTES

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You have a challenge ahead. You need to draw cubes without looking at cubes. Your friends should swear you copied them. Why do this? Drawing an accurate cube without reference gives you the most basic foundation for advanced perspective.

The Power of the Cube

Cubes provide three axes. These cover the world in all three dimensions. They use right angles strategically laid out to navigate every direction. The finale is the square faces. A square is the constant and true source of measure to eyeball proportions.

Up until now, we drew box forms without much concern for proportion. Now we want to perfect our foreshortening skills. We master proportion by seeing in simplified units. In perspective, we see in squares and cubes.

The Challenge of Proportion

It is easy to spot a square on a flat surface. Tip that flat surface in space and it becomes hard to discern. Foreshortened planes can surprise us. They lie in space. A tipped rectangle can easily look like a cube. Only the trained eye can control a true square in perspective.

Tricks to Check Your Proportions

Let's look at some tricks to build this serious skill.

  • Extend lines: A small deviation gets big if it keeps extending. A two-degree error reveals itself the further you draw it. Extend a foreshortened square to see if it is truly square.
  • Check the far plane: The hidden far side of a cube is less foreshortened. The less a plane foreshortens, the less it distorts. Look at it and adjust. Estimate first, then refine with that distant plane in sight.
  • Draw through the box: This is a reliable way to check your proportions while sketching.
  • Place circles: A square and a circle touch at four points. They stay fixed when you tip the drawing in space. Foreshortened circles become ellipses. These ellipses can give us the proportions of a foreshortened square.
  • Find diagonal vanishing points: We want to imprint the 90-degree angle in perspective. Another good angle to know is 45 degrees. Only a square gives us perfect and easy-to-find 45-degree angle diagonals.

Training Your Mind's Eye

When drawing your cubes, rehearse the three-line systems. Remind yourself that each line goes in the same direction as its neighbors. Assess each square in perspective with a critical eye.

On every square, run lines from corner to corner. Run lines across horizontally and vertically to divide the faces into segments. Out loud, remind yourself where the 90-degree and 45-degree angles sit in perspective. This prepares you to see a protractor in space.

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ASSIGNMENTS

For this assignment, you'll be using the 100 cubes you've already drawn from the last Assignment - Control Depth on Paper with a Simple Box.

Look at your rough drawings and your reference. Notice the difference.

Using your reference, sketch each one lightly and roughly again (1-2 minutes). Do not try to get the positions exact. Just place the general proportions.

Then hide your reference.

Choose the longest receding line attached to the closest corner. Darken that line. That is your source line. All other lines on this cube will be that length or shorter. Figure them out.

  • Trim planes and extend planes
  • Think through the logic
  • All planes are square
  • Try to discern that when they tip away
  • Draw through completely.

Deadline - submit by August 09, 2026 for a chance to be in the critique video!

Carlos Javier Roo Soto
First page of finding proportions to the cube. I realize I have a long way to go, I may have to do a 100.000 cubes to get this right. But in all seriousness, I feel like my biggest hurdle with this assignment is gonna be my straight line quality and getting the lines to converge properly. The waviness of my lines is gonna make me put things in the wrong spot and distort my cubes in unintentional ways. Also, I'm not sure to be using the tricks Marshall taught properly to find the proportions. Any advice? I want to fix any issues as early as possible before doing all 100 cubes.
Sita Rabeling
I admire your work ethic Carlos! This is so motivating 👍 Thank you!
M C
20h
I have to confess: I’m scared! this is the test!!! 😱
Sita Rabeling
Ah, “See the protractor” (= geo-triangle tool?) I thought that’s important, so I tried something today and maybe learned from it. Tried it out with three of the wonkiest cubes I had, to prepare for the other 97. I might change the method though, to present those better.
Maxime Scheder
There is still a way up to a100 perfect cubes, but I'll do more as warm-up in the future ! Now that I took the picture, I see that some of them aren't exact cubes though. The thing that has always got me with perspective is this chicken-egg conundrum of the ellipse. We need a perfect square to get a perfect circle, but we use ellipses to make perfect cubes... Some day I'll crack the code.
Myles Goethe
At some point I just gave up counting XD
Carlos Javier Roo Soto
Three questions. It occur to me to use the protractor line-up it's degrees with 2 lines of the cube to find the 45-degree of the plane, I feel like that would defeat the purpose of the assignment, and as I'm writing this I realize that because of the acute and obtuse corners I would have to use different degrees and find the middle degrees between those. Am I correct? The second question is that: if adjusting the furthest plane that we wouldn't see in reality, would automatically correct the other planes? The third, am I overthinking and should I just do it and find out for myself?
Marshall Vandruff
You are correct if you mean measuring on the foreshortened views — that would defeat the purpose. The purpose, as it has been with foreshortened 90° angles, is to see foreshortening and get used to it. In this case, specific foreshortening of half a right-angle. Adjusting the furthest plane would automatically correct the other planes IF every other factor (line angles, for example) were perfect. But this is overthinking. The purpose of adjusting the far plane is to help see that more-foreshortened close plan more truly. The far plane is like a cross-examining attorney who's job is to reveal what the front plane was hiding.
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