A while ago I released a Inkscape extension that can automatically generate patterns from shapes drawn, such as bag side panels. Not everyone has access to or uses Inkscape, so I’m working on bringing that key functionality to an online tool. Nearly instant patterns for backpacks, bike bags (frame bags, top tube bags etc) and more.

Work in progress! Might have some bugs. Test with a paper model or scrap fabric before committing to your expensive materials.

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Want to support development of more free tools?

Please donate via Paypal or Ko-fi or purchase a random pattern from this website

These free tools take up a significant amount of my limited personal time so any support is appreciated 🙂

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Start Drawing!

Instructions:

Draw your shape by left mouse clicking on the canvas. Where you want a split in the pattern (new pattern piece) right click. Split points are shown with red markers.

Press enter or click the finalise button to complete the shape. Multiple PDF files will be generated containing your polygon and gusset with seam allowances calculated and tiled to fit your page size.

If you need to move the points, after finalising the shape you can click and drag the points to a better position. Click a line to add a new point, and click a point once to turn to a split point (red), twice to delete. You can also adjust the seam allowance and scaling.

Tape the edges of your printed paper together to build your pattern.

Made something cool? I’d love to see. Feel free to share your creations via the social links at the top of the page or the contact form.

Scaling:

You can choose how large you want the grid to be on the canvas, for easier snapping to the grid with more detailed pattern pieces.

The PDF is scaled based on how big each grid square is, which you specify in centimetres or inches. You can also select a segment (after the polygon is finished) to set to a known length for easy scaling.

Printing and Assembling:

Patterns must be printed at 100% or “Actual Size” or equivalent in your printer settings. Cut along the borders and tape the borders together.

Known quirks:

• Likely has bugs. Test whatever you generate with a paper model or scrap fabric before committing to fabric.
• You can draw whatever, but doesn’t mean you can sew it. For example, patterns with sharp inwards corners you will struggle to sew. Again, test on scraps before fully committing.
• Linear segments only currently. I might look into curved corners and beziers in the future. For now, just draw lots of points to simulate curves, and move the points if you need to adjust them.
• Wide gussets (wider than the paper width) aren’t tiled.

Changelog:

17 Nov 2024:

• Gusset piece dimensions listed in the PDF so you don’t have to print the pages
• One single PDF generated for the entire project

9 Nov 2024: Fixed bug when generating patterns with gussets larger than page width that caused freezing

6 Nov 2024: 3D view to help visualise your project

Perfect for gym bags, stuff sacks, barrel handlebar bags etc.

Simply cut along the marked margin border of the paper, tape together then use for your projects! Make sure to print at 100% scale, or actual size, or whatever your printer offers. Measure the diameter of the inner circle against your radius ( d = radius * 2) to check it has printed accurately

The first step most people take is using the fabric panel dimensions, and doing a simple width * height * depth calculation. This is great for calculating the volume of a rigid object, but bags are soft and deform. I’ve seen commercial companies get their published bag volumes wildly wrong by making this error.

Pattern Pieces to Finished Bag Volume

Take the example on the left on this image. Doing width * height * depth calculation would result in it having zero volume as it has no depth (just two pieces of fabric sewn together), but when it is filled, it clearly bulges out and has volume.

So how can you estimate the volume based on the dimensions of your pattern pieces?

After running many fabric volume simulations, you can use these general rules:

If your bag is cuboid shaped (cube, or 3D rectangular), multiple the width * height * depth calculated volume by 1.2 to get a more accurate estimation of the volume when bulged out.

For flatter pancake shaped flattened bags, multiply by 2 for a rough estimate.

And flat bags (flat zip pouches etc) use a paper bag problem solution:

where w is width and h is height in metres, and V is volume in m³

If you are familiar with Blender, simulating volume change is easy by adding a subdivision surface multiplier then cloth physics.

If anyone knows of a generalised equation that can estimate a volume just from width, height and depth, I’d love to know!

Dimensions

Similarly if you want a bag to fit within a set range of dimensions (such as carry-on luggage) you need to account for bulging, and scale down your pattern pieces. The shallower and more pancake shaped your bag is, the more the depth dimension will change when the bag is filled.

Finished Bag Volume

For the inverse problem, trying to calculate the volume of a finished bag (cuboid shaped e.g. a backpack), again it is best to avoid doing a simple width * height * depth calculation as this does not account for bulging.

Instead, you can use the equation for calculating the volume of a elliptic cylinder using the actual bag dimensions, not the fabric panels themselves.

Want to support development of more free tools? Feel free to donate via Paypal or Ko-fi or purchase a random pattern from this website 🙂

Have you ever tried taking a photo of your pattern pieces and tracing them in software, and the dimensions are not quite right? This tool will help you correct the perspective of your photo to assist making accurate traces digitally, for example in Inkscape or Adobe Illustrator. Only corrects 2D perspective, not 3D objects.

For best results photograph your object on a grid, or on a object with 90 degree corners with known dimensions.

• Add 4 points to your image in the following clockwise order: top left, top right, bottom right, bottom left.
• Try and make the rectangle as big as possible for the highest accuracy. You can click and drag the points after the rectangle is drawn.
• Specify the known width and height of what you have selected. The units are dimensionless.
  For example, so if you have placed the object on a grid, count the grid squares. If the object is on a A4 piece of landscape paper, you could place your points around the paper and use 290 x 210 as your aspect width and height.
• Save, then load your image into Inkscape, Illustrator etc and scale to the actual dimensions, and trace!

Drop me a message if there are issues or ways to improve. I know there is a algorithm that can estimate the perspective correction just from the drawn rectangle without needing the user to specify the aspect ratio (as used in document scanner apps), but I’ve not been able to implement it yet. The method I use here should be more accurate anyway however as there is no estimation, the user specifies the known width and height.

Features

15 Litre Capacity. Volume is calculated from fabric modelling software for accuracy.

Low Profile Shape to keep out of your way during activities

Simple Design. A perfect building block to add the features you need

Great First Backpack Project. Learn to sew zips and curved panels.

Front Panel Opening with long zip for easy access to the full bag contents.

Gentle S Shaped Straps.Simple, reliable shape and design. For fully featured straps with pockets see one of my thru hiking pack or trail running pack sewing guides

Printable PDF Pattern and Full Instructions

US Letter, A4 and A0 paper sizes

Every step is illustrated and described for complete clarity. No confusing wall of text or half-baked video like you can find elsewhere.

Sew your own commercial quality backpack with beginner friendly instructions.

Not for commercial use.

FREE/Donate What You Want at PayHip

Show off your hard work!

Instagram @pricklygorse #pricklygorse

Facebook @pricklygorse

Or feel free to send me photos via the contact links at the top of the page!

Suggested Fabrics and Hardware (Notions)

This is to give a rough estimate for budgeting. The sewing guide provides a complete comprehensive shopping and cutting list and should be used over this.

Links to example fabrics at RipstopByTheRoll provided (USA). I earn a tiny amount of coffee money at no cost to yourself to support more free patterns. See my page on recommended myog suppliers for alternative suppliers

Features

15 Litre Capacity. The main body is approximately 12 litre with 3 litres of additional pocket volume. Volume is calculated from fabric modelling software for accuracy.

Vest Style Shoulder Straps that hug your body for a secure and comfortable fit. Lace up straps for fine tuning the fit, but the instructions will include a piece to use this space as an additional pocket.

Several pockets for organisation and easy access to your essentials.

• 6 pockets on the shoulder straps
• Large external stash pocket (for coat, wind breaker etc), designed to be accessed on the go.
• Top zippered pocket for small items such as a phone, sunscreen etc

Hydration Bladder Sleeve on the back panel to ensure optimal hydration.

Four Point Compression on each side to ensure the bag can be cinched tight to minimise bounce.

Zip-Up Main Compartment because when you want to move fast, the faff of a roll top and it’s additional straps won’t cut it

Printable PDF Pattern and Full Instructions

The final release will include US Letter, A4 and A0 paper sizes

Every step is illustrated and described for complete clarity. No confusing wall of text like you can find elsewhere.

The guide goes out of it’s way to not only include the most comprehensive instructions, we also include a free 25 page beginner sewing ebook to get you started.

Sew your own commercial quality backpack with beginner friendly instructions.

Not for commercial use.

Join the Waiting List at PayHip

Add your email to the waiting list “product” page at PayHip and follow me on the socials at the top of the page to be the first to know when the sewing guide is released.

Suggested Fabrics and Hardware (Notions)

This is to give a rough estimate for budgeting. The sewing guide provides a complete comprehensive shopping and cutting list

Coming soon!

Get the extension for free and open source at Github

Want to support development of more pattern generators? Donate at Paypal, Payhip, Ko-fi or purchase a random pattern from this website 🙂

Example Video

Installation

Add the .inx and .py files to your Inkscape user extensions folder. You can find this by opening Inkscape Preferences (Edit-Preferences) and selecting the System tab. Restart Inkscape and the extension will appear under Extensions – Prickly Gorse – Unroll Path to Straight Path.

Usage

Select your path (or multiple individual paths) and run the extension (Extensions – Prickly Gorse – Unroll Path to Straight Path).

Shapes need to be converted to paths (Object – Object to Path).

The extension can either generate a new straight path with the nodes at the same spacings, number the nodes, label segment lengths, extrude the line to a 2D shape, and add an offset to the extruded shape. You can chose the units, decimal precision, and label prefixes.

This produces a line slightly above the original path’s bounding box that is the total length of the path, with nodes placed the same distances along as on the original path. You can generate either a single line (A), a line and an extra group with numbered nodes (B) or labelled segment lengths in the units of your choice (C, D). You can add a label prefix, for example if making a top and bottom line.

Numbered nodes are useful if you can’t remember which node aligns with which on the original shape. If you have drawn the original path in the wrong order and don’t like your starting node, chose your new starting node and use the ‘Break Path at Selected Nodes’ tool, then re-run the extension. Or trace over your old shape with a new path, which is a bit more reliable if you want to keep it a closed shape.

But we are on MYOG Tutorials, so you probably are using this to help making sewing patterns. Using the offset and extrude options (E,F), you can make a complete sewing pattern with just a click

Top Tube Bag Example

Known Issues

Adding offset (seam allowance) to the original shape is still a bit experimental, and the offset path can sometimes be inside the original shape, or the ticks might be instead. You might need to reverse the path. Alignment marks are always added perpendicular to the path, so sharp corners will have two marks.

Sometimes the generated paths might be placed on the wrong position on the canvas, depending on how you selected the path within groups. If this happens, exit out of the group, and reselect. Don’t use CTRL+click to select into groups before running the extension.

I’d love to see the awesome stuff you make with the extension!

Contact me on the social media links at the top of the page (#pricklygorse) or contact form at the top of the page 🙂

Features

32L Capacity, shaped to maximise carrying capacity. Ideal for day trips and overnighters.

Carry on Compliant. Save money and time when flying! 48 x 35 x 24cm to fit the majority of airlines, and the instructions include guidance on how to adjust the dimensions to fit your preferred airline restrictions.

Note: the volume is calculated in software as 32 litre, but it is quite a large bag compared to other bags I have around with a similar quoted volume.

Several thoughtfully placed pockets, many of which are optional if you would prefer a streamlined bag. Ample room for essential tech gadgets, documents, accessories, toiletries, snacks, and more.

• Dedicated laptop pocket separate from the main compartment, with false bottom and it’s own volume, so you can always get your laptop in and out regardless of your packing.
• Two front pockets with their own volume, separate to the main compartment
• Under lid pocket
• Inside pockets
• Side stretch pocket, because hydration is important.
• Base rain cover pocket

Clamshell suitcase-style opening, enabling seamless packing and organisation, and easy access both during transit and at your destination. Also includes guidance for how to build as a bottom hinge bag instead.

Security. Pick pocket protector tabs on the zips to protect your valuables.

Durable design. Every seam has reinforcement stitching, and the pattern is designed to accommodate durable #10 sized zips, all while being designed to be as accessible as possible for most sewing machines.

Rain protection. Storm flaps around the main compartment zips if not using a waterproof zip, and a pocket on the base to store a rain cover.

Comfy carry handles.

Lighter than off the shelf travel packs. This example pack made from 420D nylon, 70D inner liner fabrics and foam in the back panel weighs approx 700g.

Protection. The laptop pocket has a false bottom so your laptop will never touch the floor. Padding in the back panel, side panels and pocket divider give your laptop maximum protection.

Ergonomically designed shoulder straps taken from my multi-day hiking backpack patterns, to ensure comfortable carry even after hours spent navigating busy terminals or exploring new cities. These can take an optional stretchy shoulder strap pocket, similar to that found on ultralight backpacks. Additional guidance is provided describing how to make them removable, if preferred.

Many off the shelf travel packs come with sub-par straps, yours does not have to.

Designed for your body. My partner can’t find a large travel pack that fits because of the long torso lengths of store bought packs. When you make your own gear, you can make it to your own body.

The instructions describe how to adjust the strap positions to suit you, with optional load lifters.

Travel Ready. Stashable shoulder straps for snag-free transport.

Removable hip belt. The pattern includes instructions for a removable webbing hip belt, with advice on making a padded hipbelt.

Printable PDF Pattern and Full Instructions

US Letter, A4 and A0 paper sizes

Every step is illustrated and described for complete clarity. No confusing wall of text like you can find elsewhere.

This is a relatively complicated build, but the instructions are catered as much as possible to people with only modest sewing experience. The guide goes out of it’s way to not only include a free 25 page beginner sewing ebook to get you started, but I’ve also included a scaled practice pattern so you can experiment with the techniques before going all in on the main backpack. The scaled practice pattern is completely unique to MYOG Tutorials, and I will hopefully be including this in upcoming releases.

The text includes options at tricky steps for people with lower powered sewing machines.

Sew your own commercial quality backpack with beginner friendly instructions.

Not for commercial use.

£9.99 Download at Payhip

Get your free packing cube patterns for the backpack

Prices may include digital tax if applicable in your country.

Show Your Builds!

Suggested Fabrics and Hardware (Notions)

This is to give a rough estimate for budgeting. The sewing guide provides a complete comprehensive shopping and cutting list