The goal of interactive walkthroughs in three dimensional computer reconstructions is to give people a sensation of immersion in different sites at different periods. Realism of these walkthroughs is achieved not only with detailed 3D models but also with a correct illumination regarding the means of lighting in those times. Working on the enhancement of the visual appearance of the computer reconstruction of the Gallo-Roman forum of Bavay, we propose a model that reproduces the shape, animation and illumination of simple flames produced by candles and oil lamps in real-time. Flame dynamics is simulated using a Navier-Stokes equation solver animating particle skeletons. Its shape is obtained using those particles as control points of a NURBS surface. The photometric distribution of a real flame is captured by a spectrophotometer and stored into a photometric solid. This one is used as a spherical texture in a pixel shader to compute accurately the illumination produced by the flame in any direction. Our model is compatible with existing shadow algorithms and designed to be easily incorporated in any cultural heritage real-time application.