Name: Game Physics - Introducing Gravitation & Rotation in Unity
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Created byBen Tristem

Last updated 1/2019

English

What you'll learn

Translate new laws of physics to code.
Understand how game engine physics works.
Extend the capabilities of Unity 3Ds physics engine.
Transfer this knowledge to other game engines.

Course content

4 sections • 45 lectures • 5h 13m total length

Promo Video1:25
Are You Ready For This?3:10
IN THIS VIDEO...

What you'll need to start

A Mac or PC that can run Unity 3D or similar.

You can use another game engine if you like.

Some coding experience (see sample code).

Some understanding of mechanics & units.

Confidence in basic algebra.
Welcome To The Course1:48
IN THIS VIDEO...

An overview of the interface

How to search for things

Summary
Installing Unity 3D2:54
IN THIS VIDEO...

Download, Install & Register Unity

SOME USEFUL LINKS...

Unity - Download Archive

(NOTE YOU CAN CLICK THESE LINKS BELOW)
Section Summary3:45
Section End QUIZ

Introduction To Section 21:26
In this section we will be dealing with a rigid body, and the effect of forces on it.

Unbalanced forces lead to accelerations.

Accelerations lead to a change in velocity.

Velocity determines the change in position.

We will be working backwards through this list, starting with position and eventually creating components to model the effect of various forces on our game object.
Section 2 Assets0:04
Section Notes PDF13:00
Newton's 1st Law12:40
IN THIS VIDEO…

Introducing Sir Isaac Newton

Newton's First Law

About the FixedUpdate() loop

Updating transform.position

SOME USEFUL LINKS...

Using FixedUpdate() - Execution Order of Event Functions

(NOTE YOU CAN CLICK THESE LINKS BELOW)
Summing The Forces11:13
IN THIS VIDEO...

Create A Force List

using System.Collections.Generic;

Create a public list of forces, forceVectorList;

Create AddForces () so sum the forces.

Debug.LogError () if we have a net force.

Otherwise continue to update the position.
Newton's 2nd Law8:48
IN THIS VIDEO...

2nd Law Defined

Write Code For Acceleration

Publicly expose float mass

Create UpdateVelocity () method

Modify velocityVector every FixedUpdate

Remove Debug.LogError() code
Newton's 3rd Law8:32
IN THIS VIDEO...

Defining Newton's Third Law.

Examples of why it's important to consider.

Introducing our trail drawing code.

Switching trail direction.

Recap of Newton's laws
Physics Engine Architecture15:36
IN THIS VIDEO...

What we're trying to achieve.

Why it's important to get this “right”.

Re-orgainse list iteration for variable forces.

Bring DrawTrails.cs into PhysicsEngine.cs.

Move the forces into separate components.
Mid Section QUIZ
DOWNLOAD Unity Project0:11
SI Units & Dimensions10:52
IN THIS VIDEO...

About Units and Dimensions.

Why it's worth thinking about them.

Where to annotate our units.

Prepare our RocketEngine.cs class.

SOME USEFUL LINKS...

SI base unit - Wikipedia, the free encyclopedia

(NOTE YOU CAN CLICK THESE LINKS BELOW)
Rocket Science 10116:41
IN THIS VIDEO...

The thrust of a rocket engine.

Modelling rocket engines and fuel burn.

An introduction to “delta V”.

SOME USEFUL LINKS...

Rocket engine - Wikipedia, the free encyclopedia

(NOTE YOU CAN CLICK THESE LINKS BELOW)
Modelling Gravity16:01
IN THIS VIDEO...

Review the universal gravitation equation*

Create a method for it in Unity.

Check we get realistic force values.

SOME USEFUL LINKS...

Gravitational constant

(NOTE YOU CAN CLICK THESE LINKS BELOW)
Back Down To Earth12:48
IN THIS VIDEO...

Setup a football field “on Earth”.

Test gravitation matches real values.

Explore parabolic flight.

Set scene for air resistance.
Air Resistance13:09
IN THIS VIDEO...

Design a simple formula for air resistance.

Create an Air Drag component.

Test flight against reference ball.

Tweak to get similar results to Unity's engine.

SOME USEFUL LINKS...

Drag (physics)

(NOTE YOU CAN CLICK THESE LINKS BELOW)
Script Execution Order10:33
IN THIS VIDEO...

Expand on Unity's script execution order*

Demonstrate our bug at “high” speeds.

Show how this relates to fixed update time.

Move Universal Gravity to separate object.

SOME USEFUL LINKS...

Execution Order of Event Functions

(NOTE YOU CAN CLICK THESE LINKS BELOW)
Making A Simple Game19:51
IN THIS VIDEO...

Make a simple hit-the-target game.

Add a cylinder to represent a rocket launcher.

Write Launcher.cs class.
Finishing & Tidying Up5:44
IN THIS VIDEO...

Re-introduce Universal Gravitation.

Review the overall structure of what we've done.
Section 2 Wrap-Up2:43
WHAT YOU'VE LEARNT...

Basic physics engine architecture / trade-offs.

A foundation in Newton's Laws of Motion.

Dimensional checking as a tool.

How to distill information from Wikipedia etc.

How to create components for various forces.
Section End QUIZ

Introduction To Section 31:57
Section 3 Assets0:05
Section Assets Pack

Previous section project, for Magnus Effect
Section Notes8:00
Unstable Rotation In Unity 58:37
The limitations of spinning objects in Unity 5.

Why unstable rotation doesn't evolve.

How to model unstable rotation in game physics.
Introducing Inertia Tensors13:39
Roughly what is an inertia tensor (I)?

Unstable intermediate axis

How Unity Calculates I

Calculate I for your phone

Predict it's unstable axis
Calculating Moment Of Inertia11:35
How about if two axis are equal?

Try it with a spinning cylinder.

Calculate the moment of inertia.

Render vs. collider mesh influence.
Parallel Axis Theorem10:19
NOT the same as Intermediate Axis Theorem.

How to calculate I for compound objects.

Think of a discus thrower.

http://en.wikipedia.org/wiki/Parallel_axis_theorem
“Newton’s Laws Of Rotation”8:45
A recap of Newton's laws of motion.

How these relation to rotation.

Important differences.

Why we're jumping in the deep end!
Applying Torque To Rigidbodies11:02
How to use Unity's AddTorque() method.

How Inertia Tensor affects rotation.

Comparing the rotation of two objects.
Vector Cross Products7:13
What a cross product is.

Why they are so useful.

Using WolframAlpha to calculate.
The Magnus Effect11:10
What the Magnus Effect is.

How we can approximate ball flight with it.

Using Vector3.Cross in Unity.

The code you need is below...

public float magnusConstant = 1f;

private Rigidbody rigidBody;

void Start () {
rigidBody = GetComponent<Rigidbody> ();
}

// Update is called once per frame
void Update () {
rigidBody.AddForce (magnusConstant * Vector3.Cross (rigidBody.angularVelocity, rigidBody.velocity));
}
Section 3 Wrap-Up2:37

Introduction To Section 42:40
Your Section 4 Assets0:03
Your Section Notes7:00
An Overview Of Friction8:25
Why friction is so important.

About physics materials and friction.

How static and dynamic friction relate.

Using the Friction Direction 2 setting.

Limitations of Unity's friction, and to improve it.
Static Friction & Critical Angle10:35
Welcome “Mu-s”, the coefficient of static friction.

What the static friction coefficient means.

How this coefficient relates to slope angle.

Two triangle trigonometry take-home tricks.

Testing critical angle in Unity Editor.
Make A Friction Test Rig8:55
Discover slipping angle.

Try three different static friction coefficients.

About rolling, and “impulsing” the block.

Generally horsing around with blocks and slopes.
Friction Combine In Unity3:46
Why we care about friction combine.

The limitations of Unity's model.

How friction combine precedence works.
About Dynamic Friction5:32
What is dynamic friction.

How it relates to terminal velocity on a slope.

A look at some Stribeck curves.
How Friction Direction 2 Works3:43
What the Friction Direction 2 setting does.

How it might be useful.

A note on using unit vectors.

Friction Direction 2 doesn't work in Unity 5!
Wrap-up & Next Steps2:45
Congratulations and how to continue your learning.

Requirements

You need to be comfortable with Unity 3D
You need to be comfortable with C# scripting.
You should be able solve basic algebra equations.

Description

Learn to build your own game physics engine. By the end of this mini-course course you will have gained confidence in translating theories of physics into working game code.

I will be teaching using Unity 3D free as the example game engine. I expect you to have some experience with both Unity 3D, and C# before starting this course. If you don't then check out my Complete Unity Developer course.

Why would you take this course?

To understand game physics better.
Practice creating your own physics components.
Improve your knowledge of Newtons Laws of Motion.

Note: We are no longer actively supporting this course, however if we do revisit this subject in the future then students on this course will get the updated content.

Access to this course does come with an optional, free community site where you can share games and 3D models, as well as connect with other students.

See you in there!

Who this course is for:

This course is ideal for you if you're running into the limits of your game engine's physics.
If you are not confident in how your game engine's physics works "under the hood", this course will give you that insight.
This course is probably not for you if you're a physics PhD, who is already confident in coding!

What you'll learn

Explore related topics

Course content

Introduction & Setup5 lectures • 13min

Newtons Laws of Motion18 lectures • 3hr

Simple Rotation12 lectures • 1hr 35min

Making Contact10 lectures • 53min

Requirements

Description

Who this course is for: