|Excessive volume warning [message #13611] Fri, 11 June 2010 18:08 UTC
Sometimes I find in the Gallery some models with excessive volume (no walls) or with overlapping figures, well I think that after seeing they cost hundreds or thousands of dollars. I suppose they are wrong models that shouldn't be exposed/sold, but maybe the author doesn't know his fault. Those models could give the wrong idea to future creators/buyers that 3D printing is very very expensive. Also, they are expending Shapeways' web resources (disk, database).|
So my suggestion is the creation of some volume tests after the model is uploaded (and the resulting price is high):
If the sum of the volumes of all the "solids" in the STL file is greater than the volume of the bounding box of the total figure, then they are overlapping in a high degree (this method doesn't detect small overlappings). The creator should get a warning message about this and link(s) to tutorials/posts about using boolean union to get a unique solid. Also a suggestion about deleting his model or reuploading a fixed version.
2. Not hollowed
If the ratio between figure volume and bounding box volume is high, then the figure is not hollow, it lacks walls. Again a warning to the creator with info links.
I think that both detection methods are easy to code and doesn't need a lot of cpu time. However, the detection of small overlappings is another problem and the only quick-but-not-precise solution that I can suggest is to check if the bounding boxes of the solids overlap. This will show the warning in some valid models with multiple parts (boat in the bottle, bird in cage), but the text in the warning should be clear about these cases.
Every creator should check his models before uploading, but we are lazy, we don't read the instructions or forget them, so those checks after uploading could be great.