image-to-ring

This is a command line utility that allows you to wrap an image (interpreted as a grayscale heightmap with black = 0 and white = 255) around a cylinder in order to create a 3D model (an STL file). This is primarily useful for creating rings and texture rollers.

Installation

1. Clone this repository.
2. Install OpenSCAD.
   • These instructions assume you are running Windows. If you install somewhere other than the default location (C:\Program Files\OpenSCAD\openscad), you'll have to update the path in image-to-ring.js with the installation directory.
   • On MacOS you might have to follow these instructions to get the command line interface to OpenSCAD working. You'll also have to update the path in image-to-ring.js with the correct installation directory.
3. Install Node.js.
4. Run npm install from the root directory of this repo.

How to Use

As a quick start, or to check if everything is installed correctly

node image-to-ring.js

Options

The following are the available command line options in this project. Please refer to this diagram for the bolded terms used in this document:

• -i <image-path>
--image <image-path>
  Specify the path to the raster image (png files recommended) you want used as a heightmap for the model. Make sure to surround the path with quotation marks.
  • Defaults to "input.png".
• -r <radius>
--radius <radius>
  Define the radius of the cylinder (in mm) that the image heightmap should be built on top of.
  • Defaults to 8.545.
• -t <heightmap-thickness>
--thickness <heightmap-thickness>
  What is the desired heightmap thickness in mm? That is, given an image that contains at least one pixel of full white (#ffffff), how thick should the heightmap be from the highest point to the radius of the cylinder.
  • Defaults to 0.5.
• -h <hole-radius>
--hole-radius <hole-radius>
  How big should the ring hole radius be in mm? Set this to 0 to have no hole at all (a full cylinder).
  • Defaults to 0.

Examples

Here are some model screenshots and the images/commands used to create them.

William Morris Venetian Ring

node image-to-ring.js -i assets/william-morris-venetian.png

Maze Ring

node image-to-ring.js -i assets/maze.png -h 7.445

Sinusoid Pattern Ring

node image-to-ring.js -i assets/sinusoid.png -h 7.445

Minkowski Curve Ring

node image-to-ring.js -i assets/minkowski-curve.png -h 7.445

Circles Ring

node image-to-ring.js -i assets/circles.png -h 7.445 -t 2 -r 6.945

Brick Texture Roller

node image-to-ring.js -i assets/brick-texture-roller.png -r 25 -t 2

Notes

• Generating the 3D model is extremely slow (especially if hole radius != 0). If you are iterating quickly, I recommend using a reduced resolution version of your image during the design process.
  • In the future, I'm hoping to move to a different technology to improve performance.
• By making the hole radius > radius, the bottom of the heightmap (darkest areas) will cut all the way through the ring, allowing for some interesting results.
  • If you do this, make sure hole radius - radius > 0.001 or the design might not actually cut through the surface.
• If you are intending to make a ring, this table of ring sizes in several different measurement systems is useful.
• The height of the cylinder that's generated depends on the aspect ratio of the input image and the cylinder radius specified. As such, you may need to compute a good aspect ratio for the image to get the desired ring width.
  • To compute the image aspect ratio a for a desired ring width w, you can do:
    • a = 2 * radius * π / w
  • As an example, let's say I want to create a US size 4 ring with a total ring thickness of 1.6mm and a width of 5mm. If we assume a heightmap thickness of 0.5mm, that means we need a base thickness of 1.6mm - 0.5mm = 1.1mm. A US size 4 ring has an internal diameter of 14.89mm or a hole radius of half that: 7.445mm. That means the cylinder radius is 7.445mm + 1.1mm = 8.545mm. Plug that into the equation and we get: a = 2 * 8.545 * π / 5 ≈ 10.7. That means the image aspect ratio needs to be about 10.7:1.
• Using GIMP's Bloom filter (Filters -> Light and Shadow -> Bloom) can create nice gradients in designs that result in a scalloped effect.
• There are various services that will 3D print a ring in metal for you from a model. However, be aware of the use of conflict minerals in this process before you decide to proceed.