Statistics - Sketch
Description: Sketch

Next: Bugs and anomalies, Previous: Hidden surface removal, Up: Hidden surface removal

##### 4.4.3.1 Statistics

For the curious, `sketch` writes one line of depth sort statistics. Here is an example for a large collection of triangles.

      remark, node=34824 probe=581.9 swap=5 split=2 (in=4 out=6) ols=24851/0

It means that 34,824 objects were depth sorted after culling. For each, an average of 581.9 others had to be checked to ensure that the initial, approximate ordering was correct. Among all these checks, only 5 resulted in swaps to reorder the initial sort. In two cases, a correct ordering could not be determined, so binary space partitions were constructed for splitting. A total of 4 objects (triangles in this case) were inserted in the partitions, and 6 polygons were produced. Finally, 24,851 “last resort” polygon overlap checks were performed after simpler, faster checks failed to yield conclusive results. The final /0 is for line-polygon overlap checks. For comparison, the statistics for the last figure in Overview follow.

      remark, node=27 probe=14.6 swap=36 split=15 (in=30 out=45) ols=0/69

Note that there was proportionally much more swapping and splitting activity in this highly connected scene.