du -sh *

Linux disk space usage, in human readable form. Nuf said.

std::nth_element

Ever wanted to know what the N:th element in a sorted version of the sequence [first,last) is, without sorting the whole thing? I sure did. Unfortunately I didn't know about std::nth_element!

std::nth_element( first, nth, last );

Paraphrasing sgi.com, after this function is applied, nth is guaranteed to be the same as if the entire sequence was sorted. Meanwhile, non of the (first,nth] elements are larger than the nth element, and so logically the opposite goes for the [nth+1,last) elements. This method does less work than both std::sort and std::partial_sort, and thus is likely to be faster.

float2 and float3 in Maya Python API

Staying true to form, Autodesk sure has made a mess of the Maya Python API. Something I ran into recently was dealing with float2:s (for MFnMesh::getUVAtPoint()). Turns out you need to go through MScriptUtil like so:

import maya.OpenMaya as om
# this creates the float2
pArray = [0,0]
x1 = om.MScriptUtil()
x1.createFromList( pArray, 2 )
uvPoint = x1.asFloat2Ptr()
# (call to OpenMaya.MFnMesh.getUVAtPoint( ..., uvPoint, ... ) 

# goes here)
# retrieve results

uv0 = om.MScriptUtil.getFloat2ArrayItem( uvPoint, 0, 0 )
uv1 = om.MScriptUtil.getFloat2ArrayItem( uvPoint, 0, 1 )

Curiously enough the '2' in float2ptr and float2array refers to 2-dimensional arrays, hence the extra 0 in the call to the latter. We're only dealing with float2& (which typedefs to float[2]) in our getUVAtPoint call, but frankly: did you expect anything else than a hackfest when you popped that Maya 2009 box open?

Python stack trace

Outputting the stack trace can be immensely useful in certain situations.

import traceback, sys

def bar():
   raise Exception('Booboo')

def foo():
   bar()

try:
   foo()
except:
   traceback.print_exc()
print 'Got here.'

Result:

Traceback (most recent call last):
  File "./foo.py", line 14, in 
    foo()
  File "./foo.py", line 11, in foo
    bar()
  File "./foo.py", line 8, in bar
    raise Exception('Booboo')
Exception: Booboo
Got here.