Our Unity Tutorial on Augmented Reality Game Development with Vuforia SDK

Unity AR Tutorial: Augmented Reality Game Development with Vuforia

 

Vuforia is an AR platform that provides amazing opportunities for augmented reality development. Here are some examples:

Vuforia also has a Unity SDK and in the second part of this tutorial  I’ll explain how to integrate and develop it. But let’s start with the Vuforia integration…

Obtaining a Vuforia license

add_license_keyThe first thing you have to do is  register on Vuforia page. After you complete the registration process, you can start developing with Vuforia SDK. You will then need a license for your project.

Head over to the Development tab, and click on the “Add license” button. A little form will show up. Fill in the form as shown on the side and click “Next”.

Then you have to confirm your license key by agreeing with terms and conditions and by clicking “Confirm”. Pretty simple so far, right?

Vuforia’s Unity SDK

It’s time to download the Vuforia SDK for Unity. You can download it in the Vuforia Downloads tab.

unity_sdk

After downloading the package, import it into the existing project inside of Unity.

Prepare the markers

Now it’s time to prepare the markers. Markers are the images that Vuforia will use as the points of reference to display your objects. The more distinct key points the image has, the more accurate or “augmentable” your markers will be. The easiest way to create such  marker is to generate a QR code. QR codes have a lot of key points and they work like a charm. You can generate them yourself or, to make it quicker, you can download mine 🙂

create-databaseOnce you’ve got the marker, it’s time to upload it to Vuforia. Go to the Vuforia Target Manager page and click on the “Add new database” button. Type the preferred name for your database and choose the “Device” as a Type option.

 

Great! Now, select the name of the database you’ve just created and then click on the “Add the new target” to the database.

add-target

Select the Single Image type, pick the marker you’ve downloaded before, set the width to 1, name it the way you want it and click “Add”.

There are other types of targets, for example Cuboid, Cylinder or a 3D object. These can work as 3D markers (you can make them if you feel like it), but preparing them would take a lot more time, because you’d have to create and upload every side of that cuboid to Vuforia and that’s a chore…

Alright, so now you can see your target has been added to the list and it’s ready to be downloaded. Click “Download Database” and import the package to Unity.

Preparing the scene

Setting up the scene is also very easy. Get rid of the existing camera on the scene. Vuforia has its own camera that your scene will use. Drag and drop ARCamera prefab from Vuforia > Prefabs folder into the scene. Your scene hierarchy should look like this:

unity-scene-image

Now, let’s setup the ARCamera properties. ARCamera prefab requires the license key which you can find on the Vuforia License Manager Page.

AR license key

Copy and paste your License key to Vuforia Behaviour Script field of the ARCamera prefab on the scene.

unity-scene-with-script-image

Select ARCamera in your hierarchy, and in the Database Load Behaviour tick the “Load [name] database” checkmark, then “Activate”.

database-load-behaviour

Setting up the markers

Alright, now it’s time to add the markers on the scene! You can do it by dragging ImageTarget prefab from Vuforia > Prefabs to your scene.

Your ImageTarget needs to be set to a specific marker image. It has a script called “Image Target Behaviour”, where you can do that by choosing your database name in the “Database” field and then select the “ImageTarget” from the drop down list. It should look like this:

image-target

Great, you’re almost done! Now it’s time to add some objects to the display. Right click on the ImageTarget in the hierarchy, 3DObject > Cube. Resize the cube the way you want it and the project is ready to be compiled! Alternatively, you can add any 3D object to the hierarchy of the ImageTarget.

As you can see, Vuforia SDK is very easy to setup and it has a lot of nice features you can utilize to make awesome games or apps. For example, you can combine a couple of those markers to make something a bit more complicated like this:

Procuring Graphical Assets

You will need some 3D models. I’d suggest that you download and import these amazing drone models by Popup Asylum.

Next, we’ll need a QR code as an additional marker. You can generate your own, but feel free to use mine if you’re lazy 🙂 Also don’t forget to upload it to the Vuforia Target Manager page and download the updated database after that.

For the testing purposes you’ll need these two markers printed, so I’ve also prepared a pdf for you to download.

A few more textures for you to import: drone_shadow, white_ring.

Scene setup

Drag and drop 2 ImageTarget prefabs from Vuforia > Prefabs to the scene. Name the first one as “DroneTarget” and the second one as “GoalTarget”. After that assign the corresponding “Image Target” to each one of them in the Image Target Behaviour Script. In the same script, change the width of the DroneTarget to 3 and GoalTarget to 2. It should look like this for the DroneTarget:

dronetarget

And like this for the GoalTarget:

goaltarget

Now in the ARCamera object in our hierarchy, head over to the Vuforia Behaviour Script and change the value of “Max Simultaneous Tracked Images / Objects” to 2. Then in the “World Center Mode” section select “SPECIFIC_TARGET” from the drop down list and in the section “World Center” choose the DroneTarget from the hierarchy. It should look like this:

ar-camera

Connecting Models to Markers

We’ve got the markers, let’s add the 3D models they will represent…

Right click on the DroneTarget and select “EmptyObject”. Make sure this new object has a position of [0;0.5;0] and scale of [0.33;0.33;0.33]. I’ve also changed the name of it to “Drone”. Then, add a 3D model of any drone as a child to this object and change the position of it to [0;0;0] and scale to [0.33;0.33;0.33]. Now the hierarchy looks like this:

drone-model-setup

So, let’s add a model for our GoalTarget. Add an empty object same way we did for the DroneTarget and change its name to “Ring”. Then add a Sprite Renderer to that object and in the “Sprite” section, choose our ring sprite. After that you can change its color to whatever you’d like. You also might want to resize it, change the position to make to fit the QR marker. It kind of looks like this for me:

all-model-setup

Nav Mesh setup

Alright, so we’ve got the scene, let’s now get to the main functionality… Pathfinding. So we need to bake a Nav Mesh. For more info, please, go to Unity navigation tutorial page.

Baking a Nav Mesh requires a presence of a regular mesh on the scene to walk on first. Right click on the hierarchy 3D Object > Plane. Rescale the plane so it covers an area around the markers where you potentially would like your drone to move. Now open up the navigation window (Window > Navigation) and in the Object tab make sure your plane is selected along with a “Navigation Static” checkbox. After that click “Bake”. Fantastic! If your scene looks somewhat like this, you’re on the right track!

navmesh-with-plane

So what do we do with that annoying white plane obstructing the view? Well, it’s time for us to get rid of it. Yeah, just delete it, we won’t need it anymore, since the Nav Mesh is already baked.

Once we’ve got our Nav Mesh, it’s time to setup a Nav Mesh Agent, an actor that would travel using the Nav Mesh. The Nav Mesh Agent functionality should obviously be applied to the drone, so select the first child in the “DroneTarget” hierarchy…

select-the-drone

… and add NavMesh Component to the inspector. You’ll see a whole bunch of parameters for this component. I’m not going to explain what each and every one of this parameters means since that’s not the point of the tutorial. (If you’re interested in the commentary over the parameters, please watch this video and here’s Unity docs). Here’s a screenshot of my Nav Mesh Agent parameters for the drone:

nav-mesh-agent

Coding time

The initial scene setup is ready and it’s time to write some code for it to work… Create a script in one of your folders and add it to the “Drone” object (DroneTarget first child).

The whole moving mechanic is pretty simple. We’d need two variables variables:

A function to track a position of the second marker and move the drone towards it:

That’s it. Just execute this function in the update and don’t forget to select the “Ring” (GoalObject child) object as a public variable in the inspector.

movement-script

You can now build the project onto your phone and check whether it works with the markers.

NOTE: The DroneMarker should always be in the camera view for the whole app to work since we’ve declared it as the world center and the whole drone logic is attached to it.

Drone leaning

You might also want your drone movement look more realistic, so let’s add movement leaning. The done will lean forward depending on its current speed.

MapRange function

There’s a great function I use pretty often called MapRange. It converts numbers within a range to numbers within another range depending on the current value.

A simple example of this function working is… let’s say we want to change the color of the ball depending on player’s distance from it. s would be our current distance from the ball. a1 – minimum observed distance, a2 – maximum observed distance. So we want the ball to be blue if the distance is more than 3 meters and red if player is 1 meter away or less. everything in between would be automatically purple -ish. So the implementation with MapRange would look like this:

playercolorball

Back to the drone leaning…

so in case of movement leaning, exploiting MapRange() would be this simple:

Add PitchCtrl() to the update function and you’re good. The drone will lean forward while moving.

Shadow

Let’s add a shadow to the drone. A simple static shadow. That’s a piece of cake since we just have to add a sprite to the existing hierarchy. Make sure your shadow object is the second child of “Drone”. Just like that:

first-shadow

Line renderer

In order to setup a line renderer we should add a sprite, but don’t worry, there’s no need to import one, just head over to your project window and open the folder where you store your sprites. Hit Right click > Create > Sprites > Square. You’ve got your new sprite which we’ll use for the new material that we’re about to create.

Right click > Create > Material. Material’s shader should be changed to Particles > VertexLit Blend and Particle Texture to the earlier created Square sprite. Sounds hectic, but just look at this picture and you’ll get it:

laser-material

Create a new script. Let’s say the name of this script is Goal. Attach the Goal script to our Ring object.

ring-line-renderer

Also attach line renderer component to the “Ring”. Line renderer would require a material, so please add the material we just created to it.

line-renderer

So, it’s time to write the code, which is also very simple. Here the whole Goal script code and it’s pretty much self-explanatory:

If you run the app now, you’ll see the ring’s line/laser pointing to the drone destination. It’s great but we can also make this destination look a little bit more clear by adding another object… Just a game object containing a Sprite Renderer and Animation components.

destination play

Create a public variable destSprite and update MoveToTarget() function.

That’s it, run your project on a smartphone and you’ll have the same result as in this video:

Thanks for reading and don’t forget to subscribe to our newsletter not to miss any of the new Unity development blog posts!

Optimize yourself! [Part 2]

Things you can do better in Unity!

This is the second part of our tips list, that can help you increase your productivity with Unity.

The first part can be found here. So definitely check it out if you haven’t already!

1. Unity project setup wizard

When you’re creating a new project it often takes at least half an hour to setup everything. There are at least 2 ways for you to save time here:

  1. Simple: create a project template with basic setup, folder structure and version control ignore file. This will be the most efficient one to make and you can put stuff in it already. But it is not the most customizable one, so probably you will need to spend this additional time on finishing your configuration.
  1. Advanced: create a module that will be responsible for setting up your whole project in a way you want it. With as many game/folder structure/architecture variants as you’d like to have. And in a perfect world, it would be great to have such module but it takes time to make it.

No matter which option you choose, it is always helpful to have a solid foundation for you project 😉

2. Finally you drag the list of objects into the component

Sometimes you may come across a case where you have to fill the list of objects with objects from a scene or a project. When you’ll first try to select all of the objects you’d like to assign, you’ll realise that Inspector is no longer showing you object with your list to fill. There is a very simple solution to that, and not many people know about it.

In a top right corner of Inspector there’s a lock button, that locks Inspector focus on current view.

Now you can select as many objects as you like and you can easily drag and drop them all into the list in Inspector.

Done!

3. Use build-in json tools

Normally, when you are working with JSONs, you have to have JSON parser. After parsing a string into JSON object, you have to assign all the values from JSON to the desired object, which is super boring to write each time…

However, since the Unity 5.3 they gave us built-in JsonUtility which will do most of it for you!

Warning: JsonUtility currently works only with ‘structured’ JSON and does not support types, like dictionaries. If this is a problem for you, then you probably need to find a fully-featured JSON library.

For more information about JsonUtility you can go to: https://docs.unity3d.com/Manual/JSONSerialization.html

4. One script that handles all of the platforms?

If you are new to programming, you probably don’t know much about platform dependent compilation. If you are into programming, then you have probably seen a code that uses platform dependent compilation a few times, but you might not understand how it works. It’s simple! It gives you the power to write the code that will be executed only on a specific platform. So you might ask why it’s good to use it? Because you can use libraries designed only for one platform.

For example: you are making the greatest game of all time for Android and iOS. And you want to implement that last feature, namely leaderboards. You’ve created a button to show these native leaderboards and assign method OpenMainLeaderboard() to it. And now it’s time to implement this method, but how will you run Google Play Services on Android and Game Center on iOS?! That’s simple! Use platform dependent compilation!

Example:

With that you don’t have to worry about the missing references from libraries that are not designed to run on other platforms.

If you’d like to find more platform directives go to: https://docs.unity3d.com/Manual/PlatformDependentCompilation.html

5. Don’t waste your time for reimporting project over and over again

Aren’t you tired of waiting for your project to be reimported each time you change build platform? For me it’s not only boring, but also wasting a lot of time! But there is a mighty solution for that, which no one ever told you about!

In Unity there is something called Cache Server. It can be configured to work on your local machine or on a dedicated server. This cache server will save your reimported assets and when you change your build platform, it will give you back your reimported assets, so you don’t have to reimport them again! This is great! And the only thing you have to do is to go to Unity > Preferences > Cache Server and change Cache Server Mode to Local or Remote.

You can read more about Cache Server on our blog:

http://blog.theknightsofunity.com/using-unity-cache-server/

http://blog.theknightsofunity.com/unity-cache-server-localhost-make-sense/

Summary

That was top 10 things that you can do better in Unity (with those in the  previous part)!

I hope that this list will help you save a little more time that you will still waste by watching another cat video on the internet 🙂

If you have your own trick to speed up your work, then don’t hesitate to share it in a comment section below.

And don’t forget! Optimize yourself!
You can also subscribe to our newsletter, so you won’t miss our posts in the future!

Optimize yourself! [Part 1]

Things you can do better in Unity!

How many times you’ve been bored or annoyed because of some stuff you had to do over and over again? Probably countless… But fear no more!

Bill Gates once said “I choose a lazy person to do a hard job. Because a lazy person will find an easy way to do it.”.

And you might ask why even I’m bringing this quote here? It’s because I am going to make you lazy in a good way… 😉

Let’s get it started

The main reason we came up with idea for that list is the fact that we (as  humans) are lazy by design and we don’t like to repeat ourselves in our daily tasks. As a  result, we came up with tools and tricks that we use to make our life easier and we hope to make it easier also for you!

So here are top 10 things you can do better in Unity:

1. Change your play mode editor color!

How many times you’ve been tweaking your game to be in this one perfect spot? And all of a sudden you realized that you just clicked on pause button and lost all of those changes? Of course this is how Unity works, but how many times you forgot about it? Probably not only once. 😉

So the simplest solution to remind you that you’re in the play mode is to change editor’s play mode color! To do so, just go to Unity > Preferences > Colors and change your Playmode tint color to something more vivid.

Results?

2. Let the code write itself

There are many tools that can extend your IDE and give you just a little bit of support for your programming skills. One of such extensions is JetBrains ReSharper which is so useful that you probably won’t want to program anything without it.

This tool analyzes the code for you. This tool writes the code for you. This tool finds bugs for you. THIS TOOL EVEN FIX THOSE BUGS FOR YOU! Maybe not all of them, but it fixes the typical ones without any problems 😉 If you are programmer then you should definitely check it out.

Here are some examples:

  • Converting code to Linq:

  • Converting code from Linq:

  • Adding missing usings:

  • Generating methods:

Home page of ReSharper: https://www.jetbrains.com/resharper/

3. Optimize your build pipeline

When you’re developing your next very best app or game you are probably making a lot of builds per day. Each build can take up a few minutes or even an hour to make. This is bad especially because it’s impeding your work till the build is finished.

So let’s count the time you waste because of that process. Let’s say that your project is medium sized and need ~20 minutes to build on Android and ~1 hour to build on iOS. And you’re making 1 build per day at minimum. Now let’s sum up the time it takes to make those builds in one month (20 work days): Android builds – at least 6h 40m. iOS builds – at least 40h. This is more time than it took first spacecraft (Luna 1) to make flyby of the Moon in 1959! Which took only 36h! But how to save so much of your time? Use external tool to make those builds for you!

For a long time, the most popular one was Jenkins, which offers you a lot of flexibility. Also, it’s giving you basically unlimited possibility to configure your build pipeline to suit your needs, for example:

  1. Watch repository for new commits.
  2. Analyze code.
  3. Make a build.
  4. When finished, send build file to a FTP server.
  5. Send mail with a build report and a link to build file.

Of course there are a lot more options, and if you ever need more, then you can always add some. Oh, and I almost forgot! It’s available for free! So you just need to go to their website, download it and install it on your build machine 😉

More about Jenkins: https://jenkins.io

The other tool is provided by Unity itself and it’s called Unity Cloud Builds. It of course assures better integration with editor, where you can basically configure everything you need to start using it. Like Jenkins, it is also available for free, but with Unity subscription your builds will be higher in priority list and will be processed faster. Additionally, after each build Unity generates the link to your build to download or to share with your friends 😉

More about Unity Cloud Builds: https://unity3d.com/services/cloud-build

So what are differences between these two? Jenkins is open-sourced and has a huge library of plugins to install. You can for example integrate 3rd party APIs like Slack with it. Jenkins also allows you to configure it any way you like it and give you a possibility of setting up your own build pipeline. On the other hand, Unity Cloud is only focused around Unity and you can’t add anything to it. Of course you can configure Slack to get notifications from Cloud or use Webhooks that Unity provides, but that’s it. But the advantage is that it is straightforward, easy to configure and use.

Which one should you use? If you need something simple, then go with Unity Cloud Builds. If you need something more advanced, with a lot of configuration options, then go with Jenkins.

4. Store your data in convenient way

Many people put the data into objects on a scene or hardcode it somewhere else. With that approach it’s often hard to find where you have to make a change in order to achieve a desired result later in development…

But we’re here to present you two better ways to store data:

  1. Text Asset, which can be JSON, Excel file or any other text format. The problematic aspect of it is that in such file you can put only text, and you need to have a parser to read this file and get your data.
  2. The other and more convenient way is to create ScriptableObject. You can put there anything you like. Text, numbers, textures, material, models, etc. And most important thing is that you can use it like any other asset in your project and reading data from it is as easy as getting a variable.

Here is an example of ScriptableObject code:

And with that code you can easily create as many WeaponData objects as you want 😉

5. Auto references

Creating UI is not the most pleasant thing to do, mostly because you have many scripts, that need even more references, which you have to assign by hand. Wouldn’t it be great to have all of these references filled all by themselves?

Of course! Here is a sample implementation for that:

Here is class example of use of that implementation:

Here is how it looks in Unity:

These references were added automatically! 😉

Summary

So, here’re 5 tips that hopefully can help you exclude a chore part from the Unity development process and boost your productivity. I’ll be adding more tips like that in the next part, so stay tuned!

You can also subscribe to our newsletter, so you won’t miss our posts in the future!

MonoBehaviour call optimization for Unity developers

MonoBehavior calls optimization

What if I told you that Unity can be wasting a lot of CPU performance just by calling your MonoBehaviour functions? It doesn’t really matter what your scripts are doing. If you have hundreds or thousands of them, you should be aware that there’s a new field of optimization.

Magic methods

MonoBehaviour functions calls are slow. And I’m talking about functions like Update(), LateUpdate(), OnRender() etc. They are so-called magic methods, and if you’re familiar with object-oriented programming languages, this concept looks like calling a method using reflection mechanism (reflection enables method calls even if you don’t know the interface). Reflection calls are expensive, so Unity does everything that is possible to cache any operations, so the set of CPU instructions needed to call a magic method each frame could be minimal. But it can still be slow, very slow…

Why is it so slow?

I’m not gonna talk about the details (but if you really want to read about the details, look at the end of this article for the links), so just imagine that Unity tries to be as flexible and easy to use as possible. Making something easily costs CPU power because the engine cannot make any assumptions about your game and it needs to do a bunch of checks to call your magic functions on the right objects, in the right order, and to not crash in the meantime.

Can it become faster?

Oh this is my favorite part. Yes! It can! How? You have to take the responsibility of calling Update() function by defining your own function and calling it from a manager. This way, you’re taking responsibility for updating your objects. How much faster it can become? Well, it depends on the platform. Let me use the measurements done by Valentin Simonov on official Unity blog:

Mono with fast but no exception settings.

Here you see that the difference can be worth the time. This is a measurement of calling Update() 10000 times.

Writing a manager

I will present a fairy simple example of a manager called BoxManager that is managing BoxManaged scripts. Manager has two responsibilities:

  1. Keeping the list of managed objects updated
  2. Calling update-like functions on managed objects when manager Update() is called.

The code may look like this:

As you can see, it’s really simple. Before implementing Update() function let’s take a look at BoxManaged.cs.

It registers itself when enabled and de-registers when disabled. Fair enough. ManagedUpdate() function is a function that will replace Update() magic function. Let’s implement BoxManager.Update(), so it will be able to call all BoxManaged.ManagedUpdate() at once.

And that’s it! Really! Now in ManagedUpdate() you can do everything you would normally do in the Update() function.

Please note that I did not use foreach for iterations. Firstly, because it’s generating small amount garbage Unity’s version of Mono. Secondly, because it simply seems to be slower.

Should I care?

It depends on what kind of game are you creating and what is the target platform. Ask yourself a question – do you have many MonoBehaviour objects with Update() calls? It doesn’t necessarily need to be Update(), it can be anything that it is invoked with each frame. Then, if you’re targeting mobiles, it’s definitely worth to try! Targeting standalones? It’s still something you may consider, especially if you’re planing to have huge amount of objects.

Sometimes you may need a manager even if you’re have a relatively small amount of objects. On iOS there was (I don’t know if it has been fixed or not) a problem with OnRender() function. Having it on 30-40 objects could decrease the game’s performance twice! The solution? A manager like the one presented above, but instead of calling Update() it should be calling OnRender() code. Yes, it will work!

Please keep in mind that this is one of many optimization strategies that you can use. Yet this one is quite hidden – unless you know about it, you will have a hard time to find about this one. That’s the reason why this article has been brought to life.

References:

https://blogs.unity3d.com/2015/12/23/1k-update-calls/

 

Snow Shader Tutorial with Unity

Let It Snow! How To Make a Fast Screen-Space Snow Accumulation Shader In Unity

Have you ever wondered how much time does it take to apply snow to all of the textures in your game? Probably a lot of times. We’d like to show you how to create an Image Effect (screen-space shader) that will immediately change the season of your scene in Unity.

3D model house village with trees in the background in Unity

How does it work?

In the images above you can see two screenshots presenting the same scene. The only difference is that in the second one I enabled snow effect on the camera. No changes to any of the textures has been made. How could that be?

The theory is really simple. The assumption is that there should be a snow whenever a rendered pixel’s normal is facing upwards (ground, roofs, etc.) Also there should be a gentle transition between a snow texture and original texture if pixel’s normal is facing any other direction (pine trees, walls).

Getting the required data

For presented effect to work it requires at least two things:

  • Rendering path set to deferred (For some reason I couldn’t get forward rendering to work correctly with this effect. The depth shader was just rendered incorrectly. If you have any idea why that could be, please leave a message in the comments section.)
  • Camera.depthTextureMode set to DepthNormals

Since the second option can be easily set by the image effect script itself, the first option can cause a problem if your game is already using a forward rendering path.

Setting Camera.depthTextureMode to DepthNormals will allow us to read screen depth (how far pixels are located from the camera) and normals (facing direction).

Now if you’ve never created an Image Effect before, you should know that these are build from at least one script and at least one shader. Usually this shader instead of rendering 3D object, renders full-screen image out of given input data. In our case the input data is an image rendered by the camera and some properties set up by the user.

It’s only the basic setup, it will not generate a snow for you. Now the real fun begins…

The shader

Our snow shader should be an unlit shader – we don’t want to apply any light information to it since on screen-space there’s no light. Here’s the basic template:

Note that if you create a new unlit unity shader (Create->Shader->Unlit Shader) you get mostly the same code.

Let’s now focus only on the important part – the fragment shader. First, we need to capture all the data passed by ScreenSpaceSnow script:

Don’t worry if you don’t know why we need all this data yet. I will explain it in detail in a moment.

Finding out where to snow

As I explained before, we’d like to put the snow on surfaces that are facing upwards. Since we’re set up on the camera that is set to generate depth-normals texture, now we are able to access it. For this case there is

in the code. Why is it called that way? You can learn about it in Unity documentation:

Depth textures are available for sampling in shaders as global shader properties. By declaring a sampler called _CameraDepthTexture you will be able to sample the main depth texture for the camera.

_CameraDepthTexture always refers to the camera’s primary depth texture.

Now let’s start with getting the normal:

Unity documentation says that depth and normals are packed in 16 bits each. In order to unpack it, we need to call DecodeDepthNormal as above seen above.

Normals retrieved in this way are camera-space normals. That means that if we rotate the camera then normals’ facing will also change. We don’t want that, and that’s why we have to multiply it by _CamToWorld matrix set in the script before. It will convert normals from camera to world coordinates so they won’t depend on camera’s perspective no more.

In order for shader to compile it has to return something, so I set up the return statement as seen above. To see if our calculations are correct it’s a good idea to preview the result.

RGB Rendering of Camera Space for Unity Shader Tutorial

We’re rendering this as RGB. In Unity Y is facing the zenith by default. That means that green color is showing the value of Y coordinate. So far, so good!

Now let’s convert it to snow amount factor.

We should be using the G channel, of course. Now, this may be enough, but I like to push it a little further to be able to configure bottom and top threshold of the snowy area. It will allow to fine-tune how much snow there should be on the scene.

Snow texture

Snow may not look real without a texture. This is the most difficult part – how to apply a texture on 3D objects if you have only a 2D image (we’re working on screen-space, remember)? One way is to find out the pixel’s world position. Then we can use X and Z world coordinates as texture coordinates.

Now here’s some math that is not a subject of this article. All you need to know is that vpos is a viewport position, wpos is a world position received by multiplying _CamToWorld matrix by viewport position and it’s converted to a valid world position by dividing by the far plane (_ProjectionParams.z). Finally, we’re calculating the snow color using XZ coordinates multiples by _SnowTexScale configurable parameter and far plane to get sane value. Phew…

Unity Snow Texture for Unity3D shader tutorial

Merging it!

It’s time to finally merge it all together!

Here we’re getting the original color and lerping from it to snowColor using snowAmount.

The final touch: let’s set _TopThreshold value to 0.6:

Voila!

Summary

Here’s a full scene result. Looking nice?

Lowpoly Township Set on the Unity Asset Store

Low Poly 3D Snow Village Unity Asset Shader

Feel free to download the shader here and use it in your project!

Scene that has been used as the example in this article comes from Lowpoly Township Set. Inspired by this particular redditor.