Free Armature of the Rectangle Grid Generator
Overlay the armature of the rectangle instantly with our 100% free grid generator. Upload any painting or photo and all 14 lines and 37 crossings redraw live for its exact aspect ratio, then export SVG or 600 DPI in seconds. No signup, no downloads needed. Trusted by 60,000+ artists worldwide.
Diagonals and their perpendiculars
The armature of the rectangle: both diagonals, plus lines dropped perpendicular to them from the remaining corners, and the halving lines. The intersections are the classical harmonic points of a frame, which is what the construction exists to find.
Fixed geometry, free placement
The figure itself is determined — there is nothing to set, because the construction has no free parameters. Colour, width and opacity are yours, and the overlay carries its own transform, so it can be moved, scaled and rotated over the image independently.
Stacks with composition & photography
Overlays combine, each carrying its own transform, so this one can sit under or over rule of thirds, golden spiral and golden spiral, and 15 more in the same set.
A full harmonic set on one sheet
All the lines export together at up to 600 DPI, or as SVG paths so a dense armature stays legible when enlarged. Grid-only on transparency for reuse.
| Ctrl + Z | Undo |
| Ctrl + Y | Redo |
| Esc | Deselect overlay |
| Alt + drag | Free positioning (no snap) |
| Ctrl + scroll | Zoom canvas |
| Ctrl + P | |
| ? | Show this help |
Fourteen lines built from nothing but the four corners and the four edge midpoints, crossing at thirty-seven points that stay in the same relative places whatever aspect ratio you work at.
The armature grid generator draws one of the 82 composition overlays in Grid Maker Pro, and the rest stack on the same image.
- 14 lines
- 37 crossings
- SVG + 600 DPI export
- Nothing uploaded
What is an armature of the rectangle?
The armature grid generator is a free browser tool that constructs Charles Bouleau's 14-line armature of the rectangle over any image or blank canvas. The construction uses only the frame's four corners and the midpoints of its four sides: two corner-to-corner diagonals, eight half-diagonals running from each corner to the midpoints of the two opposite sides, and four lines joining the midpoints of adjacent sides. Those fourteen lines meet at 37 distinct points, 29 of them inside the frame. Because no length enters the construction, the crossings sit at the same fractions of the width and height on a square, a 3:2 frame and a 16:9 crop alike.
How to use the armature of the rectangle
The fourteen lines of the classical armature over your own canvas, so the diagonals, the reciprocals and the points where they cross are visible while you are still composing.
Open the armature overlay
Open the tool with the armature already constructed for the canvas you are on. The fourteen lines derive from the frame itself, so there is nothing to measure and nothing to set before you can read the crossings.
JPG · PNG · GIF · WEBP
Bring in your frame
Work on the blank canvas at your paper size, or drop in a photograph or a work in progress. The armature carries its own transform, so you can drag, scale and rotate it over the artwork without moving the artwork.
Armature (14-line) · line colour · opacity
Place against the crossings, then export
Put the subject on one of the four eye points and a counter-element on a half-diagonal. Drop the opacity until only the crossings you are working to still read, then export SVG for a plotter or a raster at up to 600 DPI.
PNG · JPG · PDF · SVG · up to 600 DPI
Three steps, about a minute. No signup, no upload.
What the Armature Grid Generator does
Fourteen lines, not approximately fourteen
The armature of the rectangle is fourteen lines derived from the frame, which is what keeps its crossings exact. Sketched by hand the half-diagonals drift: a line aimed at an edge midpoint lands near it, and every crossing it makes moves with the error. Constructed, each line ends exactly where the frame says it should.
Thirty-seven crossings, and you can count them
Eight of the thirty-seven sit on the boundary — the corners and midpoints the figure is built from. The twenty-nine inside the frame are the ones you compose against, and knowing the number is what stops you claiming any placement is on the armature.
The same points at any aspect
Nothing in the construction refers to a length, so stretching the rectangle moves every line and leaves every crossing at the same fraction of the width and height. Solve a placement on a 3:2 frame and it is still solved when the client asks for the square crop.
Over your own image, not beside it
The armature is drawn on the canvas your photograph or painting is on, with its own transform. You are checking the composition you actually have, not comparing it with a diagram in another window.
Readable, because you can turn it down
Fourteen lines at full strength is a thicket. Per-overlay colour and opacity let you fade the web until only the crossings near your subject register, which is the difference between using the armature and being buried by it.
Vector out, at print size
SVG export gives real lines you can scale, plot or cut. Raster export is sized from the paper format and the DPI you choose, up to 600, rather than from whatever your browser window happened to be.
Armature of the rectangle examples: four ways the armature reads
Armature of the rectangle vs drawing it by hand on the work vs a downloaded armature template image
| Option | All 14 lines, exactly placed | Over your own image | Vector export | Cost |
|---|---|---|---|---|
| Grid Maker Prothis tool | Yesconstructed from the frame | Yeswith independent transform | SVG + raster to 600 DPI | Free |
| Drawing it by hand on the work | Only as accurately as you aim | On the surface itself | No | Time, and it marks the surface |
| A downloaded armature template image | Whatever aspect it was made at | Only in a separate editor | Rarely | Free or paid |
| Guides in a page-layout or photo editor | Yesif you place every line yourself | Yes | Yes | Subscription |
Who an armature of the rectangle is for: frames that have to hold more than one thing
How an armature of the rectangle works — Fourteen lines, thirty-seven crossings, and why the frame's own corners are enough
The armature of the rectangle is the most over-claimed of the 82 composition overlays and also one of the most useful, and the two facts are related. Almost everything written about it describes a slightly different set of lines. Here is exactly which fourteen this tool draws, what they do, and what the construction guarantees on any frame.
Start with a rectangle and refuse yourself a ruler. The only points you are allowed are the four corners and the midpoints of the four sides — and midpoints you can get by folding, so no measurement is involved. Every line in the armature is drawn between two of those eight points. That constraint is the whole idea: a composition system that needs no external ratio, no φ, no √2, nothing but the frame you already have.
Fourteen lines come out of it. Two are the corner-to-corner diagonals. Eight are half-diagonals: from each of the four corners, one line to the midpoint of each of the two sides that corner does not touch. The last four join the midpoints of adjacent sides, inscribing a diamond in the rectangle. There is no vertical or horizontal centre line in the set — the medians are absent, and the centre arrives anyway where the two diagonals cross.
The armature is what a rectangle says about itself when you give it nothing to work with but its own corners.
Thirty-seven crossings, twenty-nine of them usable
Fourteen lines meet at ninety-one points at most. They meet at thirty-seven, because the construction is dense with concurrences — three and four lines passing through the same point, again and again. That redundancy is what makes those points feel structural rather than accidental.
Eight of the thirty-seven are the boundary points the figure was built from: four corners, four edge midpoints. That leaves twenty-nine interior crossings. It is worth knowing the number, because the standard failure with the armature is deciding after the fact that a subject was on it. With twenty-nine points and fourteen lines across a frame, almost anything is near something. Naming the four or five crossings a composition is actually resting on is the discipline the system asks for.
Why it does not care about your aspect ratio
This is the property most descriptions miss, and it is the practical reason the armature outlives fashions. Because no length appears in the construction — only corners and midpoints — the entire figure is affine-invariant. Stretch the rectangle horizontally and every line stretches with it, and each crossing stays at exactly the same fraction of the width and the same fraction of the height.
Construct the armature on a square, on a 3:2 frame and on a 16:9 crop, normalise the coordinates, and you get the same thirty-seven points in all three. Nothing drifts toward the centre on a square. Nothing spreads toward the corners on a panorama. This is testable rather than asserted, and it is why a composition solved on one crop survives being reframed for another.
The fractions it hands you
Those crossings do not land on arbitrary decimals. On both axes they fall at sixths, fifths, quarters, thirds, two-fifths, halves, three-fifths, two-thirds, three-quarters, four-fifths and five-sixths of the frame. Eleven simple fractions on each axis, produced by drawing lines between corners and midpoints, with no arithmetic anywhere in the process.
The rule of thirds generator draws points that are in that set exactly, not approximately. Which explains something practitioners notice and rarely account for: an armature composition and a thirds composition seldom fight each other. Thirds is a strict subset of what the armature offers. The extra twenty-five interior points, and the diagonals connecting them, are the entire reason to reach for the longer construction.
Where it came from, and what is honestly claimed
The system comes from one book: Charles Bouleau, a French painter, published Charpentes: la géométrie secrète des peintres in 1963 — in English, The Painter's Secret Geometry. He overlays armatures and root rectangles on Giotto, Piero della Francesca, Raphael, Vermeer, Velázquez, Poussin and Cézanne, and argues that a shared skeleton of construction lines governs where their major elements sit. That book is what put the phrase "armature of the rectangle" into studio vocabulary.
What Bouleau offers is visual correlation drawn after the fact, not documentary evidence that any of those painters set out fourteen lines. The armature overlay page takes that question further, beside the other advanced composition overlays. The defensible reading is narrower and more interesting: trained painters internalised the structural skeleton of a rectangle and resolved compositions onto it without naming it. Treat the armature as a way of seeing what a frame is already doing, rather than as proof of what a dead painter intended.
How to actually use it
The order matters: compose first, overlay second. The armature is a verification instrument. Used the other way round, as a template to compose onto, it gives pictures that read as mechanical to most viewers — and the reciprocal lines generator is the lighter construction to reach for when fourteen lines is too many. Block the picture the way you would anyway, then turn the fourteen lines on and ask which relationships they resolve — whether the subject is sitting on an eye point, whether a secondary mass is on a half-diagonal that connects it to the subject, whether the horizon has landed on a fraction or between two.
Then turn the opacity down. This is the step most people skip and the one that decides whether the armature is usable at all. Fade the web until only the crossings near your subject still register; if a placement stops looking supported when the lines dim, it was never supported. Four to six named points per image is a composition. Twenty-nine is a texture.
Where an armature of the rectangle gets used
Multi-figure work is where it pays. With three heads and a gesture to resolve, thirds gives me four points and no way to connect them. The half-diagonals tell me where the second group wants to sit relative to the first.
I shoot wider than I need and crop later. Knowing the armature is the same figure at 3:2 and at square means the placement I liked in the viewfinder is still the placement after the crop.
For a wall I am working at a size where nothing can be checked by standing back. Constructing the armature on the scaled drawing and marking the crossings gives me points I can chalk up full size.
Armature of the rectangle: frequently asked questions
The geometry
Which fourteen lines does this draw?
Two corner-to-corner diagonals; eight half-diagonals, one from each corner to the midpoint of each of the two opposite sides; and four lines joining the midpoints of adjacent sides. There are no medians in the set — the vertical and horizontal centre lines are not part of this construction, and the centre point arrives where the two diagonals cross.
Is the armature just a more complicated rule of thirds?
The thirds points are genuinely in the armature — they are among the fractions its crossings land on, exactly rather than approximately. What the armature adds is twenty-five more interior points and the diagonal lines that connect them, which is what you need when several elements have to relate to each other rather than one subject having to sit somewhere.
Which line group is the most useful?
The eight half-diagonals. They give diagonal direction without the weight of a full corner-to-corner diagonal, and they are what carries the eye between two masses that both need placing.
Did the Old Masters actually use this?
Bouleau's 1963 book shows that the lines correlate with where major elements sit in many canonical paintings, but correlation drawn after the fact is not documentation of intent. The honest claim is that trained painters internalised a rectangle's structural skeleton and resolved compositions onto it without naming it.
Can I use it on a blank canvas rather than a photograph?
Yes. Set the paper format you are working to and the armature constructs for that canvas, so you can mark the crossings before there is anything on the surface. That is the usual workflow for panel and mural planning.
Using it
How many intersections does the armature have?
Thirty-seven distinct crossing points. Eight of them are the boundary points the construction is built from — the four corners and the four edge midpoints — which leaves twenty-nine interior crossings to compose against.
Do the crossings move when I change the aspect ratio?
No. Nothing in the construction refers to a length, so the figure is affine-invariant: every crossing stays at the same fraction of the width and the same fraction of the height whether the frame is square, 3:2 or 16:9. That is why a placement solved on one crop survives being reframed for another.
How do I stop fourteen lines from swamping the image?
Turn the overlay's opacity down until only the crossings near your subject still read. If a placement stops looking supported when the lines fade, it was not supported. Working to four to six named points per image is the whole technique.
There are no controls. How do I make it less dominant?
Through the line style, which is all this overlay has. Fourteen lines at the default black-at-60% is a great deal of ink, so drop the opacity well down and use auto-contrast to pick a colour that separates from the picture rather than competing with it.
How do I fit it to a crop rather than the whole frame?
Drag and scale the overlay to the crop you are considering. The construction is derived from a rectangle's corners and side midpoints, so it genuinely changes when the rectangle does — which is why checking the armature before you commit to a crop is worth more than checking it after.
Export and print
Can I export it as an SVG?
Yes. SVG export gives true vector lines, which is what you want for plotting, cutting, or scaling to a size no raster would survive. Raster export goes to 600 DPI and is sized from the paper format you chose rather than from your browser window.
Can I print it to work over a painting?
Export the lines alone at the panel's proportion and print onto acetate. Print at the proportion rather than fitting to a sheet — the diagonals have to reach the actual corners, and a letterboxed print puts them somewhere else.
Which format for a large reproduction?
SVG. Fourteen lines, several of them long diagonals, is the worst case for raster stair-stepping, and it costs nothing to export vector instead. At A2 the difference is plainly visible.
Choosing a grid
Is this just a complicated rule of thirds?
No — they overlap by accident on some frames and diverge on most. The armature is built from corners and midpoints, so its lines move with the rectangle's proportion; thirds are always at a third whatever the frame. On a square they nearly agree, on a panorama not at all.
Practical matters
Does my reference image get uploaded?
No. Everything happens in your browser — the image is drawn to a canvas on your own device and never sent anywhere. There is no account and no upload step.
Did the Old Masters actually use it?
Bouleau argued they did, and his analyses are persuasive rather than documented — very few working drawings survive that show a ruled armature. Treat it as a strong reading of how those pictures are organised, not as a recovered studio procedure.
Open the tool Armature grid generator
Fourteen lines, thirty-seven crossings
The armature of the rectangle constructs itself over your own frame. Name the four points your composition is resting on, then export vector or 600 DPI. No signup, nothing uploaded.
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