
8. Real-Time Constructive Solid Geometry 89
Figure 8.8. Splitting a polygon with the planes of a brush.
splits on both polygons, due to floating-point imprecision. It is necessary to avoid
this to ensure that the resulting mesh is well formed, without T-junctions. As
shown in Figure 8.9 a T-junction occurs on an edge if only one face is split but the
coincident edge of the adjacent face is not. This forms a tiny crack in the mesh that
can cause flickering of pixels of the background to show through when rendering
due to discrepancies in rasterization of the two faces that use different vertices.
To help avoid T-junctions and ensure a robust mesh repr