Skinning

Introduction

How do animators make those beautiful animations

Project Set Up

1. Install miniconda

Our first step is going to be to install miniconda. This is a so-called package manager that we will use in this project for python. If you have a lot of projects, each relying on their own unique, but possibly conflicting packages, a package manager is super important to be able to properly organize your projects. Install miniconda by clicking on the appropriate download from the site according to what kind of computer you have

2. Open a terminal window

Once you have miniconda downloaded, you can check that it works by opening a terminal. In Mac/Linux operating systems, just open the standard default terminal.

In Windows, you can open the Anaconda Prompt, which should have been installed when you installed miniconda.

3. Create a new environment

Now that we have a terminal open, we can create a new environment. I usually create one new environment for each one of my projects so that I can install all the packages I want for it, without worrying how it will affect my other projects.

To create a new environment, type the following command into your terminal:

    conda create --name skinning python=3.8

This will create an environment named skinning with python version 3.8. You can change the name of the environment and the version of python to whatever you want, but this writeup will assume you are using python 3.8 and an environment named skinning.

4. Activate the environment

Now that we have created the environment, we need to activate it. This is done with the following command:

    conda activate skinning

This tells your terminal to use the environment we just created. You can tell that it is activated because the name of the environment will appear in the terminal prompt.

5. Install the required packages

Now that we have our environment activated, we can install the packages we need for this project. This is done with the following command:

    pip install -r requirements.txt

I've taken the time to put all the packages we need in the requirements.txt, feel free to have a glance at the contents of that file to see what packages we are installing.

6. Run jupyter notebook

Now that we have all the packages installed, we can run the main IDE we will be using for this project, Jupyter Notebook, which was installed by the previous command. An IDE is just a fancy word we use to describe the tool we use to look at and write our code.

To run Jupyter Notebook, just type the following command into your terminal:

    jupyter notebook

This should open a page in your favorite browser that sort of looks like a bunch of files on your computer.

Affine Transformations

$$ A = \begin{bmatrix} a_{11} & a_{12} & a_{13} & a_{14} \\ a_{21} & a_{22} & a_{23} & a_{24} \\ a_{31} & a_{32} & a_{33} & a_{34} \\ \end{bmatrix} $$

Scales, Shears and Translations

Linear Blend Skinning

$$ x_i = \sum_{j=1}^{n} w_{ij} T_j x $$

Tasks

translate.py

scale.py

rotate.py

lerp.py

slerp.py

linear_blend_skinning.py