1 Using Voxelization and Ray-Tracing to Identify Wall Thinness of ...

32Figure 19: Many voxels are flagged as unsafe when the unsafe cutoff is only one voxelIn many cases, it seemed that highlighting the voxels that were one unit of voxel distanceaway from a safe voxel only served to emphasize the edges of an object. This information isinteresting, but it was turning up too many false positives: voxels that were highlighted as unsafewere, in fact, safe to print. Though this did indeed catch overly-narrow areas of geometry, weneeded a way to reduce the number of false positives to get the final output more relevant.To try and reduce the number of false positives, we tried shifting the model slightly andrunning the algorithm again, then comparing the results. Shifting the model in space slightlywhile keeping our voxelization grid centered on the x=0, y=0, z=0 point caused the trianglegeometry to fall into different bounding voxels, thus altering the final results. However, overallwe found that this did not produce any significant effect on the number of false voxels. Thoughrotating the model or shifting the model would often eliminate false positives in one area, itwould introduce them in a new area, thereby canceling out any gain. The net effect was roughlythe same, regardless of model positioning. Thankfully, from the perspective of a 3D printer, wewould rather have false positives than false negatives. If there was a problem area in a model andthe algorithm did not catch it, that would be greater cause for concern.Another interesting byproduct that occurred when flagging all the distance-1 unsafevoxels was the introduction of artifacts. Figure 20 demonstrates this effect.