Blob Holes
This method was invented by Dave Matthews.
If you want lots of spherical or cylindrical holes that don't follow a simple
regular pattern, then the tricks shown in parts 1 and 2 are likely to be very
difficult to use. Dave discovered that it was possible to get a good speed increase
in many cases by using blobs.
In this case, a blob of 2000 randomly placed spheres is differenced from a cube in 23 seconds.
The equivalent CSG takes nearly an hour.
The method works because blobs have their own bounding mechanism which doesn't get combined
with the bounding slab of the object that the blob is differenced from. So the advantage
of efficient bounding is retained. Blob tests are considerably slower than sphere tests,
but the efficient bounding can give a speed improvement that vastly outweighs this.
Limitations
This trick only works with holes that are (optionally scaled) spheres and cylinders.
The speed improvements can be fairly modest unless the blob components are very small.
The holes can blob together if they get too close (after all, that's what blobs were designed for)
and that may not be what you wanted.
Other Tricks
Holes Tutorial Part 1
Holes Tutorial Part 2: Iso-Holes
Holes Tutorial Part 3: Transparent Holes (Bubbles)
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