Thermal Drift Density Map is an interactive artwork that visualizes the dispersion of body heat as emissions of thermal energy in the form of slow-moving packets or quanta that flow away from the participant. The project uses a thermal camera to detect heat, and a particle system to visualize its dispersion, while computational image-making reveals the porous boundary between body and environment. Thermal cameras, which are increasingly used in policing and military contexts, illustrate the asymmetrical power structure between observer and those surveilled. In such applications, body heat, an essential human signature and a signal of life, becomes a target. In Thermal Drift Density Map the camera is placed in a more playful environment to illustrate how body temperature can paint portraits.