Hey Brad, I wondered if using math directly would be faster than working with XSIMath objects, so I tried. You probably knew this, but to get a distance between two 3D vectors the formula is quite easy:
* d = √ (Ax-Bx)2 + (Ay-By)2 + (Az-Bz)2
*
where A and B are two vectors to measure from.
However, you can skip the squareroot if you're only comparing relative
distances. Squareroots can be computationally expensive.
Knowing this, I wrote a version which appears to run about 77% faster, and
it's shorter too! (It takes 4.5s testing a null near a 1000x1000 pointcloud
grid, vs your code taking about 20.3s on the same task.)
def FindClosestPoint( inObj, inPos ):
fX, fY, fZ = inPos.Get2()
pts = inObj.ActivePrimitive.Geometry.Points
pos = pts.PositionArray
d = dict( [ (i, (fX-pos[0][i])**2 + (fY-pos[1][i])**2 +
(fZ-pos[2][i])**2 ) for i in xrange(pts.Count) ] )
closestIndices = sorted(d, key=d.get)
# distance = d[closestIndices[0]]**0.5
return closestIndices[0]
I love me a Python optimization challenge. :)
Cheers,
-- Alan
ps: Friendly nod to Xavier for pointing out "**" syntax does "to the power
of" so I don't need to use math.pow() in my code.
On Tue, May 1, 2012 at 5:55 PM, Bradley Gabe <[email protected]> wrote:
> Sure, have at it:
>
> def FindClosestPoint( inObj, inPos):
> dist = 10000
> ID = -1
> Pos = XSIMath.CreateVector3()
> PosArr = inObj.ActivePrimitive.Geometry.Points.PositionArray
> for index in range(inObj.ActivePrimitive.Geometry.Points.Count):
> Pos.Set(
> PosArr[0][index],
> PosArr[1][index],
> PosArr[2][index]
> )
> Pos.SubInPlace(inPos)
> D = Pos.Length()
> if D < dist:
> dist = D
> ID = index
> return ID
>
>
>
>
> On Tue, May 1, 2012 at 5:52 PM, Alan Fregtman <[email protected]>wrote:
>
>> Care to share a sample snippet? Maybe there are even faster ways to
>> approach it.
>>
>>
>> On Tue, May 1, 2012 at 5:42 PM, Bradley Gabe <[email protected]> wrote:
>>
>>> UPDATE:
>>>
>>> All things considered, it's not too horrible simply looping through
>>> every position from the Geometry.Points.PositionArray, and comparing the
>>> distance in order to find the closest point in the cloud. So far, that
>>> technique is faster than anything else I've attempted to cook up.
>>>
>>> -Bradley
>>>
>>>
>>> On Tue, May 1, 2012 at 3:01 PM, Bradley Gabe <[email protected]> wrote:
>>>
>>>> Nah, it was raising errors when I tried it before starting this thread,
>>>> and it still is now [?]:
>>>>
>>>> # ERROR : 2028 - Traceback (most recent call last):
>>>> # File "<Script Block >", line 2, in <module>
>>>> # obj.ActivePrimitive.Geometry.GetClosestLocations([0, 0, 0])
>>>> # File "<COMObject <unknown>>", line 2, in GetClosestLocations
>>>> # COM Error: Invalid argument specified. - [line 2]
>>>>
>>>>
>>>> On Tue, May 1, 2012 at 2:58 PM, Bradley Gabe <[email protected]>wrote:
>>>>
>>>>> I was going by the following quote from the docs:
>>>>>
>>>>> Note: Point locators are currently only supported by NurbsSurfaceMeshand
>>>>>> PolygonMesh objects.
>>>>>
>>>>>
>>>>> But I'll still give it a shot...
>>>>>
>>>>>
>>>>> On Tue, May 1, 2012 at 2:54 PM, Stephen Blair <
>>>>> [email protected]> wrote:
>>>>>
>>>>>> But doesn't a PointCloudGeometry support GetClosestLocations? Can you
>>>>>> use that (I didn't try it yet) ?
>>>>>>
>>>>>>
>>>>
>>>
>>
>
<<347.gif>>
