Architectural walkthroughs using portal textures

This paper outlines a method to dynamically replace portals with textures in a cell-partitioned model. The rendering complexity is reduced to the geometry of the current cell thus increasing interactive performance. A portal is a generalization of windows and doors. It connects two adjacent cells (or rooms). Each portal of the current cell that is some distance away from the viewpoint is rendered as a texture. The portal texture (smoothly) returns to geometry when the viewpoint gets close to the portal. This way all portal sequences (not too close to the viewpoint) have a depth complexity of one. The size of each texture and distance at which the transition occurs is configurable for each portal.