Using Command Buffers in Unity: Selective Bloom

Disclaimer: This post is a bit outdated since Unity has introduced the Scriptable Render Pipeline, which Catlike Coding has a better guide on than I’ll ever put in the time to write, LOL. However, if you’re using a legacy version of Unity that doesn’t have the SRP, or you want to write a single custom pipeline effect instead of extending the SRP, then the topics covered in this post are your best bet.

What this tutorial will cover

This is a pretty hefty tutorial that covers how to use command buffers in Unity for graphical effects that require extending the graphics pipeline. I’m going to illustrate the concept of extending the graphics pipeline by explaining how I built the system that creates this selective bloom effect.

The glowing effect in this tutorial is pretty boring, since the glow is a single solid color. I challenge you to modify the glow buffer step to actually render the model or utilize a custom emission map per-object… the possibilities are endless! The possibilities of what could be contained in this tutorial, however, are finite, so that’s why we’re focusing on this solid color glow.

Credit goes to Unity’s example project for command buffers, especially the one on decals, for helping me figure out how to utilize command buffers.

What you need to start

You’ll need some basic knowledge about how Unity’s rendering pipeline works, and what rendering pipelines do in general. I also recommend you check out Unity’s basic overview of command buffers┬ábefore reading this.

You definitely also need to have some experience writing basic shaders. This blog is full of tutorials on shader writing that I strongly recommend you check out before diving into this one ;0

I also strongly recommend that you reference┬áthe Unity project on GitHub for this tutorial, as it completely implements everything we’re about to cover!

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