Digital Painting With Real Brushes: Light Strokes for IPad
Introduction: Digital Painting With Real Brushes: Light Strokes for IPad
Digital painting apps provide some amazing simulated brushes, but if you miss the expressiveness of painting with real brushes and other physical tools, then this Instructable is for you. It shows how to build the Light Strokes hardware that enables digital painting on the iPad using actual brushes, sponges, rags, or almost anything you'd care to paint with. You can even do digital finger painting. The hardware works in combination with the Light Strokes app, available for free from the App Store. You can see it in action on prototype hardware in the first video.
Light Strokes uses an optical effect you may have noticed when looking down through a glass of water and seeing just your fingertips against the side of the glass. Everywhere else, the background is seen by total internal reflection (TIR). Instead of a glass of water, here we use a Fresnel prism, consisting of thousands of tiny facets. The iPad's camera is placed where it can only see the parts of fingers, brushes, or other tools that are in optical contact with the top of that prism, the painting surface. Wetting the tools helps to eliminate the layer of air needed for TIR. As you move the tools, the Light Strokes app processes the camera's images of the contact areas into painted strokes, with your choice of colors and effects.
The materials and supplies are given at the beginning of each of the steps, with part numbers and links to manufacturers/suppliers. You will also need the following tools:
* 3D printer - all parts fit within the 300 x 220 x 300 mm build volume of a Creality CR10Mini.
* Hard rubber brayers, ~2" and ~8"
* Ultraviolet (UV) lamp (ZHMA 60 w)
* Glass cutter for thin glass (Fletcher 01-128)
* Running pliers (Fletcher 06-111)
* Saw that can cut aluminum, preferably a table saw
* Drill, preferably a drill press
* #4-40 tap and tap handle
* 3/16" hollow hole punch (Harbor Freight 3838)
* Soldering iron
* Goat hair lens brush (Matin M-6328)
Step 1: Laminate Painting Surface
The painting surface is the most critical component. Scratches can show up as unwanted lines in every painting, and beads of water can paint unwanted spots. 582
You will need:
* Tempered Glass, 10" x 12-1/2" x 3/16" - Glass is more wettable and scratch-resistant than most plastics, and tempered glass has even greater strength and scratch resistance. Most glass companies can supply tempered glass, cut it to size before tempering. Ask them to sand (not bevel) the edges, and for "no logo" or "paper logo only" (instead of marking the glass itself).
* Fresnel prism - This is made by 3M as "Brightness Enhancement Film" (BEF), and you'll need the kind that uses 90° prism facets oriented in parallel, such as BEF4 GT 90/24 or BEF2 T 155n, available in 450 mm square sheets from 3M distributors (American Polarizers Inc. XN400032068 or XN400033769). BEF comes with protective films on both its flat and prismatic sides, which should be kept on for as long as possible since the prisms are easily scratched.
* Adhesive - The flat surface of the BEF must be laminated to the glass in a way that doesn't damage the prisms, remains clear, and contains no air bubbles (which can also spoil every painting). This lamination method comes from an Instructable by <PERSON>. It uses a UV-curable Liquid Optically Clear Adhesive (LOCA) (DUV TP-2500), which comes in a 50 g syringe, though only about 15 g is needed for one painting surface.
Before beginning the lamination, you should know how the BEF is oriented. The film on its smooth side is yellow, while the one on its prismatic side is clear. If you place it smooth side down, with the corner notch at bottom right, then the prism facets (facing up) will run left/right, as shown in the picture. That's the same orientation you'll want when laminating, with the longer (12-1/2") dimension of the glass also running left/right.
To double check, remove a small piece of both films at a corner (which will be discarded later). Note that you can hear the prisms when you scratch them with your fingernail in the direction perpendicular to their grooves. There's no such texture when scratching the smooth side, in either direction. 276