cross product of two vectors

[s...@weacceptyou.com]

Hello,

i have been using this method to get the cross product of two vectors:

#####

pt1=cmds.pointPosition('locator1')
pt2=cmds.pointPosition('locator2')
pt3=cmds.pointPosition('locator3')

vec1=pm.dt.vector=(pt2[0]-pt1[0],pt2[1]-pt1[1],pt2[2]-pt1[2])
vec2=pm.dt.vector=(pt3[0]-pt1[0],pt3[1]-pt1[1],pt3[2]-pt1[2])

perpenVec=vec1^vec2

####

with the '^' symbol this process works when i tried it at home on maya 2015 in python tab of script editor.

I dont know what has changed but when i tried it at work using maya 2016 in script editor it returns this:

# Error: TypeError: file <maya console> line 14: unsupported operand type(s) for ^: 'tuple' and 'tuple' #

i don't think i have done anything different in my new script as it seems to match my other one. Can anyone tell me why the cross product operator ^ doesn't seem to work here?

thanks alot,
Sam

[Nicolas Chaverou]

Hi Sam,

As I was surprised your code used to work I just tried it in Maya 2014 and I have the same error than (which I expected)

Python doesn't define any vector type, only arrays or list. Thus cross product does not mean anything on arrays :)

Better store your vectors to the MVector api class. Something like:

import maya.api.OpenMaya as om
v1, v2 = om.MVector(vec1), om.MVector(vec2)
print v1 ^ v2

Hope that helps,

N.

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[s...@weacceptyou.com]

thanks man,

i cant figure out why this works in my other script, but i will use that Mvector class. thanks

Sam

[s...@weacceptyou.com]

sorry i meant to write this the first time. this seems to work:

####

pt1=cmds.pointPosition('locator1')
pt2=cmds.pointPosition('locator2')
pt3=cmds.pointPosition('locator3')

vec1=pm.dt.Vector(pt2[0]-pt1[0],pt2[1]-pt1[1],pt2[2]-pt1[2])
vec2=pm.dt.Vector(pt3[0]-pt1[0],pt3[1]-pt1[1],pt3[2]-pt1[2])

perpenVec=vec1^vec2
###

[Geordie Martinez]

you can make it a LOT easier of you just stay in pymel and skip maya.cmds. here is an example of what you’re doing:

import pymel.core as pm

# make pynodes out of each locator or transform
loc1=pm.PyNode('locator1')
loc2=pm.PyNode('locator2')
loc3=pm.PyNode('locator3')

# get the World space position of each locator
# each of these returns a Point 
pt1=loc1.getTranslation(space='world')
pt2=loc2.getTranslation(space='world')
pt3=loc3.getTranslation(space='world')

# to get vectors subtract one point from another
# returns a Vector
vec1=pt2 - pt1
vec2=pt3 - pt1

# .cross() is a method on any vector
cross = vec1.cross(vec2).normal() # add .normal() to normalize

​

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[sam williams]

cool thanks Geordie,

yea i guess subtraction bit is easier, but i would think overall both methods would take as long to write out with having to make pynodes to begin with. But its a nice alternative

thanks,

Sam

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