Thread by @phi6

Finally added alpha dithering to our particle shaders! @Skepsisology has been requesting this for ages.
We use it for 2 things: fading out smoke that's too close to the camera, and fading out smoke over lifetime.
Here's how we did it (THREAD):
#gamedev #unitytips #madewithunity

Btw here's the YouTube version that doesn't suffer from Twitter's video compression so you can see the effect clearly (2/9)

Firstly, fading out particles close to the camera. In the vert function we get the distance between the world space vertex and the camera position, and normalize that with our desired dithering distance (3/9)

In the surface (or fragment) function, we can then apply the screen space alpha cutout texture with our dithering value from before (4/9)

For dithering that's controlled by the particle system, we can send any data we want using custom vertex streams. Here we're sending a custom curve over lifetime to TEXCOORD0.z in our shader (5/9)

We can grab this data in our vertex function again (6/9)

And apply it to our screen space cutout texture as before (7/9)

For the texture itself, most games use a bayer matrix but we prefer blue noise as it looks more natural and less pattern/grid-like (8/9)

And here's some screenshots of the effect. In conclusion, it's a great way to get a stylized fading effect without translucent overdraw, and prevents the particles from obscuring the player camera (we have a lot of ridiculous over the top effects). Thanks for reading! (9/9)