8.10. Disadvantages of Octrees   

One disadvantage of octree representation is that an object or scene can only be approximated, and not fully represented (Carlbom and others 1985). This is because the octree breaks everything down into smaller and smaller blocks. Let's take the example of a sphere. An octree decomposition of a sphere, no matter how many decompositions are made, will never accurately represent the original sphere. It will be a close approximation, but properties such as surface curvature will be lost in the rendering process.

This limitation extends itself into the usability of octrees in existing graphics systems. Systems such as CAD/CAM systems often represent objects as primitives solids combined into complex objects, or using a boundary representation scheme. Once this has been converted to an octree to take advantage of easy set operations, the object cannot be reconstructed exactly in its previous form.