WALK - Realtime Architectural Walkthroughs

Clients are expected to visualise large complex architectural models given only a two-dimensional floor plan. A better approach would be to provide a three-dimensional view of the building, as seen from a hypothetical human observer. The client should be able to interactively control this observer, so that it is possible for them to explore the architecture before it is built.

The architectural model must be completely dynamic. That is, the designer must be able to make changes to the model without having to perform an expensive pre-processing phase. The only acceptable exception is pre-calculated lighting. Radiosity and raytracing schemes are far too slow to be performed in realtime. As a compromise, the system should support both dynamic lights, and more realistic pre-computed light maps.

The architectural walkthrough system described in this paper does not require any specialty hardware. It simply requires a desktop PC equipped with a recent graphics accelerator. To achieve interactive frame rates, the system uses a model that is partitioned into cells and portals. These cells and portals are stored in a cyclic scene graph. A depth-first-search starting at the viewer’s cell calculates the visible cells. Hidden cells are quickly culled by checking portals for visibility. If a portal is not visible, the cell behind it is also not visible. In this manner, a large amount of geometry can be culled away.

The results show that this cell and portal approach is very effective. In wire-frame mode, it is very clear that hidden triangles are quickly culled away. Because the system is very scalable, this statement will hold true for architectural models composed of millions of triangles.


The Engine

This engine contains a few interresting bits you may want to know about:


Download (27/6/2004):