Do you want to learn more about DOTS internals?

I hope you find your way to this article with the search for answers. I will show you quickly how to find out more about Unity and its internals. This is a great source of inspiration. As a game development student at Breda University of applied sciences, I could apply the gained knowledge from just researching the files besides in my DOTS project also in my C++ project. From the Unity source code, you can learn a great deal of general application of Data-Oriented Design or multithreading.

My teammate Menno learned a great deal from the files when the documentation stopped during his journey of creating his native containers! In case you have not read it go and check it out! Custom Native Container Part 1: The Basicshttps://dotsplayground.com/2020/03/customnativecontainerpt1/)

Where to start?

Whenever you have a Unity project and you have access to the source code of packages. Only to the C# frontend of the package not to the C++ facilities. DOTS and its related packages are written in HPC# (High-performance C#) Unity’s subset. This means we have access to its internals!

Where would they be?

Whenever we download a package in Unity they are stored at the same location D:\DOTS\Library\PackageCache (replace D:\DOTS with your project). In there you have typically a large or small list of packages depending on your project.

The important ones are for DOTS and Burst:

com.unity.burst@*

com.unity.dots.editor@*

com.unity.entities@*

com.unity.jobs@*

com.unity.collections@* - For NativeContainers

Additional maybe you want to have a look into:

com.unity.mathematics@*

com.unity.physics@*

What can you find in there?

In those packages, you can find the entire source code of DOTS and it makes it easier to understand or do research on how things are implemented. Alternatively, you can use this also as a source of reference when there is no documentation. In there you can find gems like SIMD instructions. Just check com.unity.burst/Runtime/x86/ . This will lead you to:

Official Documentation

How to search in there?

You could argue now that you could use VS and press F12 or inspect code to see the implementation of DOTS/Burst and co? This does not work as I have to tell you. If you do this you will something like this:

But this is helpful because this gives us an indication where we can find the source for this. The first indication is the namespace. The namespace tells us in which package we have to look. In this case, it will be in Unity.Entities which translates to com.unity.entities@* .

This leads us to the package and then we have to go to the right folder:

for example D:\git\DOTS-Playground\Library\PackageCache\com.unity.entities@0.6.0-preview.24 .

Now I can search for the proper file. This is the hardest task. They are not always quite obvious. In this case, they are in the folder Unity.Entities\Types .

Now I have access to the source code:

Conclusion

This is a great way to learn much about the internals. It allows you to gather a deep understanding of the architecture. If you are interested in more about data-oriented design, in general, check out Data-Oriented Design Book from Richard Fabian.

Soon I will demonstrate how this has helped me understand the level streaming (see this great video von Unite) and how to implement a rebuild all Entities Caches function together with my teammate Nielshttps://github.com/Nvs2000)