Several years ago I gave a keynote talk at the IEEE visualization conference titled Modern Trompe l?oeil.
In that talk, I used the example of Fra Pozzo?s painting on the ceiling of the church of St. Ignazio as an early example of immersive projection and virtual reality. The immersive theater in Pozzo?s case was the architectural space created by the church?s dome; today it is more likely a set of projectors in a CAVE. The goal of Pozzo?s painted ceiling was to seamlessly merge the space of the church with the heavens.
The Trompe l?oeil effect is particularly powerful for two reasons: First, the painting is viewed from the exact center of projection, which is marked by a large dot on the floor in the church. Second, the painted surface is hard to perceive, because the dome is so far away ? not noticing the surface of the painting enhances the illusion of 3D space. This painting is widely considered the most spectacular Trompe l?oeil painting of all time.