Jamphibious

How to make 2D Billboarded Sprites (With Shadows!)

There's a few important elements I like my billboarded sprites to have in order to help them feel more grounded in the world:

They need to face the player at all times ("billboarding")

They need to cast shadows on the world

They need to receive light from the world on themselves

Lets go through my set up for each of these:

1) They need to face the player at all times

To do this I attach a simple script on the sprite that looks at the main camera. Here's a pastebin of the C# script! This is the simplest part of the process as basically all it does is find the object named "Player" and then make the sprite face that direction at all times.

There's a line of logic preventing them from rotating on the Y dimension so they don't face you directly when standing above them, but of course this can be modified depending on your needs.

Easy peasy and (in my experience) works for most cases!

2) They need to cast shadows on the world

Shadowcasting for Unity's 2D sprites is possible built-in, but turned off and hidden by default (presumably since it's not officially supported and I assume not desired for most uses of 2D sprites). To access it you need to enable 'debug' mode on the gameobject itself and find the hidden "Cast Shadows" parameter.

I use "Two-sided" so the sprite shadow is cast from behind them as well as in front, but your setting will depend on your needs and context.

Once this has been enabled your sprite should be casting a shadow on the world - neat! We're like, 80% of the way there.

Now for the final element:

3) They need to receive light on themselves appropriately

Here's an example of a character facing away from a light source as well as facing it to show what I mean. Notice how when facing the light source the sprite looks a lot brighter, and she's darker when facing away from it thanks to the lack of lighting. This is the effect we're going for as it helps the sprite stand out mor than something with more static presence!

AFAIK surface lighting for sprites aren't supported built-in to Unity, but there's a wonderful custom sprite shader I use to achieve this that empowers this behaviour (EDIT: I unfortunately can no longer find the author of this shader, so here's a pastebin of it for now - please shout at me if you can locate the original creator of this so I can give them credit!).

All it requires is adding this shader to your project, creating a material from it and assigning your sprite onto the material. You'll need to play with the values on the material to find what looks best for you as it will depend on your setup and needs.

Conclusion

You should now have a sprite that receives world lighting and also casts shadows onto surfaces! Even just billboarding this way makes for a great-looking style and can really add a lot to the look of a simple sprite (and saves the headache of having to work with 3D characters hehehe)