What skills do I need to program with the FBX SDK Python?

A programmer with zero knowledge of 3DCG (let's say Mr. A) said, "Please tell me what skills you need to create a program using FBX SDK Python", so I made a simple summary.

There may be other people who have the same troubles as I expected, so I will publish it.

I made the material so that it is easy for Mr. A to understand, so the glossary may not be very accurate. Please understand what you are doing.

It is roughly divided into three categories.

Math
3DCG --Programming

Mathematics

Even with 3DCG and programming experience, it is difficult to use the FBX SDK Python without math skills. We recommend that you start by studying math.

3D vector

It is a method to express the position and direction in the three-dimensional space with three numerical values (x, y, z).

Addition / subtraction / inner product / outer product of 3D vectors are often used, so it is better to suppress them.

Degree [°] and radians [rad]

Both are units of angle. 180 ° = π [rad].

Radians are a prerequisite for understanding trigonometric functions.

Trigonometric function

It means sin and cos.

This is a prerequisite for calculating Euler angles.

Euler angles

It is a method to express the direction of rotation by rotating three times.

Quoted from Wikipedia

There are 12 ways of expression such as z-y-x and z-x-y in "Which axis should be rotated in which order?".

The following articles are detailed. [https://ja.wikipedia.org/wiki/%E3%82%AA%E3%82%A4%E3%83%A9%E3%83%BC%E8%A7%92](https: // ja .wikipedia.org/wiki/Euler angles)

Quarternion (quaternion)

It is a method to express the direction of rotation with four numerical values (x, y, z, w).

I think it's a good idea to suppress quaternion multiplication and conjugate quaternions.

The following articles are detailed. https://qiita.com/kenjihiranabe/items/945232fbde58fab45681

Right-handed and left-handed

It's about the orientation of the 3D coordinate system.

Note that this will change the positive and negative of the vector quaternion.

The following articles are easy to understand. https://ja.wikipedia.org/wiki/%E5%8F%B3%E6%89%8B%E7%B3%BB

Both of them appear frequently, so you need to be careful not to make a mistake.

3DCG edition

Even if you have experience in math and programming, it is difficult to use the FBX SDK Python without 3DCG related knowledge.

Here, we list the knowledge and skills related to 3DCG.

y-up and z-up

It is a story about whether the sky direction is the y-axis or the z-axis.

Both y-up and z-up often appear, so you need to be careful not to make a mistake.

Meters and centimeters

It is a story about whether the unit of length is 1 meter or 1 centimeter.

Both of them appear frequently, so you need to be careful not to make a mistake.

Skeleton (Bone Joint Armature)

It is the skeleton of a humanoid character.

For example, if you move your right shoulder, your right elbow will follow. However, even if you move your right elbow, your right shoulder does not move.

The relationship between such joints is expressed in a hierarchical structure such as right shoulder → right elbow → right wrist.

By setting the direction of rotation (quaternion and Euler angles) for each joint, you can determine the pose (posture) of the whole body.

See below for details. https://styly.cc/ja/tips/blender-modeling-start5-2/

T stance

T-stance is a type of humanoid character pose. It is often used as the initial posture.

Animation curve

A line graph drawn in an area where the horizontal axis is the time axis and the vertical axis is the amount of change.

For example, record the time change of Euler angles of joints as an animation curve.

See below for details. https://docs.unity3d.com/ja/2018.4/Manual/animeditor-AnimationCurves.html

frame rate

How many frames are there per second?

30 and 60 are often used.

FBX

This is a 3DCG file format.

You can save polygons, skeletons, animation curves, etc.

Programming

We have also summarized the programming skills required to work with the FBX SDK Python.

Python

First of all, you need to be able to use Python.

The following lessons are recommended. https://dotinstall.com/lessons/basic_python_v4

FBX SDK Python

Obviously, you need to install the FBX SDK Python.

See below for details.

Windows : https://qiita.com/segur/items/5d0dff790e784760a547
Mac : https://qiita.com/segur/items/e09d464b5e2ff0c8725e

Package management tool

Although not directly related to the FBX SDK Python, it is better to introduce tools to manage Python libraries.

I personally recommend Poetry.

For details, refer to the following. https://qiita.com/sk217/items/43c994640f4843a18dbe

Test framework

It's not directly related to the FBX SDK Python, but I think it will introduce a framework for writing unit tests.

I personally recommend Pytest.

For details, refer to the following. https://dev.classmethod.jp/server-side/python/pytest-getting-started/

at the end

I have listed them in a row.

It's a long way from inexperienced, but let's do our best!

I'm pleasure to be of some help.