Tag Archives: math

3D Rotations using Rodrigues Rotation Formula

The problem we are addressing here is the rotation of a general 3D vector about a given axis of rotation denoted by by radians. The Rodrigues Rotation Formula is as follows: Example: for a sanity check we can consider that … Continue reading

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Extension of 2D Complex Exponential Formula to 3D Rotation

In our previous post, we used , where and are 2D vectors and the formula rotates vector by . This idea can be extended to 3D by converting the vectors to quaternions. Assume and . Also, we consider to be … Continue reading

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2D Vector Rotation using Complex Exponential

Complex exponential formula represents the relationship between a vector and the rotated version of that vector by as where . Example: Rotate vector by . Answer: which is a vector towards Y-axis (Im axis). In python, we can compute this … Continue reading

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What is Kronecker Product?

Kronecker Product is a generalization of the outer product of two arbitrary size matrices and results in a block matrix. and then Example: Python example using numpy    

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Quaternions – Use them for Rotation and Transformation

This is the second tutorial on Quaternions. In the previous post, I explained how to use basics of quaternions from the pyquaternion python library. Check the previous post here. In this post, I will show you how to perform spatial … Continue reading

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Quaternions – How to generate and operate them in Python?

Python Package There are several python libraries (modules) that you can install. Here, I am going to use pyquaternion Installation This package can be installed as follows pip install pyquaternion Usage After installing the package, use it as follows:  Forming … Continue reading

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Linear Transformation of Random Variables

Linear Transformation of Random Variables is a very basic yet important operation in Statistics results of which are extensively used in different methods and algorithms in Machine Learning. Assume is a linear function, , where, is a random variable, and … Continue reading

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Importance Sampling – A Tutorial

Problem: Compute an expectation over a probability density function , given only samples generated from a different probability density function . We call and the target distribution and proposal distribution respectively. Solution: Draw samples from Calculate the probability of each … Continue reading

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Generating a trajectory of quaternions between two given quaternions

First, check my previous post on slerp to learn how to interpolate between two quaternions. In this post, we make a function that uses the previously developed interpolation to generate points (quaternions) between and initial and a final quaternion namely, … Continue reading

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Slerp: Spherical linear interpolation in quaternion space

in my previous post, I explained the simple Lerp method for calculating linear interpolation in the quaternion space. I also mentioned that while normalizing the output could help to get an optimized result, the velocity curve is not constant. To … Continue reading

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