Cheers, a bit of searching and I turned up some pseudo code for the “separating axis” method.

So having just implemented it in python/blender so I thought I’d share.

Enjoy

Rich

```
import bpy
import Blender
class BoundingEdge:
def __init__(self,v0,v1):
self.vertex = (v0,v1)
self.vector = v1 - v0
class BoundingFace:
def __init__(self,v0,v1,v2):
self.vertex = (v0,v1,v2)
self.normal = Blender.Mathutils.TriangleNormal(v0,v1,v2)
class BoundingBox:
def __init__(self,ob):
self.vertex = ob.getBoundBox()
if self.vertex != None:
self.edge = [BoundingEdge(self.vertex[0],self.vertex[1]),
BoundingEdge(self.vertex[1],self.vertex[2]),
BoundingEdge(self.vertex[2],self.vertex[3]),
BoundingEdge(self.vertex[3],self.vertex[0]),
BoundingEdge(self.vertex[4],self.vertex[5]),
BoundingEdge(self.vertex[5],self.vertex[6]),
BoundingEdge(self.vertex[6],self.vertex[7]),
BoundingEdge(self.vertex[7],self.vertex[4]),
BoundingEdge(self.vertex[0],self.vertex[4]),
BoundingEdge(self.vertex[1],self.vertex[5]),
BoundingEdge(self.vertex[2],self.vertex[6]),
BoundingEdge(self.vertex[3],self.vertex[7])]
self.face = [BoundingFace(self.vertex[0],self.vertex[1],self.vertex[3]),
BoundingFace(self.vertex[0],self.vertex[4],self.vertex[1]),
BoundingFace(self.vertex[0],self.vertex[3],self.vertex[4]),
BoundingFace(self.vertex[6],self.vertex[5],self.vertex[7]),
BoundingFace(self.vertex[6],self.vertex[7],self.vertex[2]),
BoundingFace(self.vertex[6],self.vertex[2],self.vertex[5])]
def whichSide(self,vtxs,normal,faceVtx):
retVal = 0
positive = 0
negative = 0
for v in vtxs:
t = normal.dot(v - faceVtx)
if t > 0:
positive = positive + 1
elif t < 0:
negative = negative + 1
if positive != 0 and negative != 0:
return 0
if positive != 0:
retVal = 1
else:
retVal = -1
return retVal
# Taken from: http://www.geometrictools.com/Documentation/MethodOfSeparatingAxes.pdf
def intersect(self,bb):
retVal = False
if self.vertex != None and bb.vertex != None:
# check all the faces of this object for a seperation axis
for i, f in enumerate(self.face):
d = f.normal
if self.whichSide(bb.vertex,d,f.vertex[0]) > 0:
return False # all the vertexes are on the +ve side of the face
# now do it again for the other objects faces
for i, f in enumerate(bb.face):
d = f.normal
if self.whichSide(self.vertex,d,f.vertex[0]) > 0:
return False # all the vertexes are on the +ve side of the face
# do edge checks
for e1 in self.edge:
for e2 in bb.edge:
d = e1.vector.cross(e2.vector)
side0 = self.whichSide(self.vertex,d,e1.vertex[0])
if side0 == 0:
continue
side1 = self.whichSide(bb.vertex,d,e1.vertex[0])
if side1 == 0:
continue
if (side0 * side1) < 0:
return False
retVal = True
return retVal
sce = bpy.data.scenes.active
tOb = sce.objects.active
tObBb = BoundingBox(tOb)
for ob in sce.objects:
if ob != tOb:
print "intersects: %u" % tObBb.intersect(BoundingBox(ob))
```