Interactive digital graffiti
This tool projects live drawings onto any surface. Digital graffiti can be used for cultural mediation, technology demos, public and corporate events. It turns the traditional graffiti gesture into an immersive, large-scale digital experience.
Context
The project explores the fusion of urban art and cutting-edge technology. Interférences, arts et technologies commissioned Art Plus Code to develop a collaborative digital graffiti system that is performant and flexible. The goal was to let artists or the public “paint” with light on architectural surfaces while keeping the fluidity, spontaneity, and texture of a real spray can.
Objectives
- Simulate the graffiti gesture with surgical precision and imperceptible latency.
- Turn physical flows (spray-can movement) into usable digital data for live visuals.
- Centralize detection so multi-user interaction stays fluid and stable.
Constraints
- Critical latency: The gap between hand movement and virtual ink must be near zero for immersion.
- Bright environments: Detection must stay robust despite strong lighting from video projection.
- Interoperability: The system must talk natively to the rendering stack via standard protocols.
Technical solution
Detection relies on Blobserver, a framework built to implement real-time detection algorithms efficiently.
Blobserver is more than a tracking tool—it is an optimized architecture:
- High performance: A main loop updates all enabled detectors and sources (cameras) together.
- Stream analysis: It isolates and tracks “blobs” (contact points or light sources) with stable algorithms.
- OSC output: Detection data becomes lightweight OSC messages sent instantly to render engines for full responsiveness.
We built Encres & lumières, custom rendering software that receives OSC and draws trails in real time—video spray-paint driven by OSC: brush position, pressure, and parameters are controlled by OSC messages from the detection engine.
- Multiple painters at once: several “cans” can draw simultaneously, each identified by an integer; force messages use dedicated addresses.
- Layers and rendering: layer separation and multiple painters.
- Artistic control: colour (with alpha), brush weight and size, drawing step, brush type, eraser, multi-image brush.
- Scaling: centre and scale factor to fit the projected surface.
- Inputs: input resolution adaptation.
- Global commands: clear canvas.
- Documentation: user manual and documented OSC messages for integration with sensors (e.g. Arduino), blob tracking, and colour-picker interfaces.
Results
Creating Encres & lumières enabled an organic user experience. The artist uses a modified spray can whose signal is interpreted in real time to produce complex trails, textures, and digital drips. Separating the detection engine from the renderer keeps the system stable even during long exhibitions.
Technologies used
- Blobserver: Detection engine and stream management.
- OSC protocol: High-speed tracking data transport.
- Vision systems: Industrial cameras.
- Encres & lumières: OSC-driven rendering software (see above).