# Using the nuke.math Python module to do Vector and Matrix operations

Nuke has its own python math module (nuke.math) that provides support for Matrix, Vector, and Quaternion classes, and useful functions to operate with them. If you need to do any maths involving vector operations in Nuke (like adding or substracting vectors, transforming vectors with transformation matrices, calculating vector reflections, inverse-projecting a 3d vector into 2d screen coordinates, etc), then the nuke.math module can be of great help.

Unfortunately, at this time there is no way to write out pixel data using python in Nuke, so the use of this module will be rather limited. However, it can still prove very useful to do any kind of vector and matrix operations between knobs, 3d objects, and even on sampled pixels (just not writing them out, unfortunately)

The documentation is a bit scarce on the nuke.math module at the moment, and the little there is is mostly a direct port from the same classes in C++. When first facing this module, I found myself having to learn how to use it the hard way, so here's some notes, examples, tips and extended documentation on the nuke.math module, hoping it will make it a bit more accessible to anyone trying to use it for the first time.

Note: Part of the descriptions of some classes and methods is taken from the C++ Plugin development documentation, but I've tried to expand a little more to give a better insight on what the different methods can be used for.

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## Comments

Yes, Michael, completely agree. It's one of those I had to learn the hard way, so I figured it would be useful to share. Plus, I learnt a bit more while writing it. Glad you liked it.

one quick question thou, I was testing out some of those function on Matrix and I found a little problem.

What I am trying to do is to get the XYZ rotation( in degrees ) from the world matrix of a Camera.

Following you tutorial everythign works fine but the final result of the rotation is a bit different from the original rotation.

what I am doing is really simple :

########################################

import math

matrix = nuke.math.Matri x4() #creating a matrix

matrixValues = nuke.toNode('Ca mera1')['world_ matrix'].getVal ue() # getting the value from the camera world matrix

print "matrixValues :", matrixValues

### adding the value from the camera to the matrix just created ###

for VAL in matrixValues :

print "VAL",VAL

matrix[matrixVa lues.index(VAL) ] = VAL

matrix.rotationOnly() #getting sure I have only the rotation values

print math.degrees(ma trix.rotationsZ XY()[0])

print math.degrees(matrix.rotationsZXY()[1])

print math.degrees(matrix.rotationsZXY()[2])

### check if values r the same

if nuke.toNode('Ca mera1')['rotate '].value(0) == math.degrees(ma trix.rotationsZ XY()[0]) : print True

else: print False

########################################

as u may see it seems that there is an approximation and we loose the last 5 digits on every value when we are adding the worldMatrix of the camera to our Matrix4, and that may be causing the little difference in the result.

Do you know by chance if that is something I did wrong or maybe if there is a work around it ?

thanks for your time

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