Unity - 2D shader / lighting like Terraria or Starbound

Question

I have a map with a lot of sprites. I could add a material to the sprite with diffuse shading and than add lots of lights. But that won't give me the result I want. And is performance heavy.

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Examples

In the first image you can see that light is generated by torches. It's expanding its light at its best through 'open spaces' and it is stopped by blocks fairly quickly.

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Here is a great example of the top layer. We can see some kind of 2D directional light? Please note that the lighting inside the house is generated by torches again. The cave on the right side shows a better example of how light is handled. Also, note the hole in the background, this is generating some extra light into the cave. As if the light is really shining through the background there.

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What I have

You can clearly see the issue here. Lights increase their intensity. And light creates a squared edge around some of the tiles for some reason. Also, lots of lights will cause performance issues very quickly.

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Raycasting?

I read that you can somehow use raycasting? To target 'open space' or something? I have no experience with shaders or with lighting in games at all. I'd love a well-explained answer with how to achieve this Terraria/Starbound lighting effect. This does not mean I'm saying that raycasting is the solution.

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Minecraft

In Minecraft, light can travel for a certain amount of air blocks. It gradually fades to completely dark. In the Graphic settings you can enable Smooth Lightning, which will (obviously) smooth the lightning on the blocks.

I guess this is done with shaders, but I'm not sure. My guess is that this is performance heavy. But I'm thinking about air blocks (which are gameobjects) and maybe I have the wrong logic.

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Note: I love a helpful answer, but please provide a link with a detailed explanation. Or provide an explanation with source code or links to the Unity docs in your answer. I wouldn't like to see theories worked out or something. I'd love to get an answer on how to implement this kind of lighting in Unity.

I'd also like to know if it's possible to NOT use a package from the Unity Marketplace.

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Similar, but no good

Take a look at similar posts with links to articles that cover the basics of raycasting. But no explanation on how to implement this in Unity and not the Terraria/Starbound effect I'd like to achieve:

Make pixel lighting like terraria and starbound

How to achieve Terraria/Starbound 2d lighting?

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Video impression

For example, take a look at this video for a really good impression on how 2d light works in Starbound:

https://www.youtube.com/watch?v=F5d-USf69SU

I know this is a bit more advanced, but also the point light generated by the player's flash light is stopped by blocks and let through by the open spaces.

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Other help forums

Also posted by me.

Gamedev Exchange: https://gamedev.stackexchange.com/questions/155440/unity-2d-shader-lighting-like-terraria-or-starbound

Unity Forum: https://answers.unity.com/questions/1480518/2d-shader-lighting-like-terraria-or-starbound.html

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Answer 1

I can mention 2 main elements about 2d Dynamic Lighting for unity.

1. One of the main asset used for 2d lighting in unity essentials is DDL light, with an official tutorial here.
2. Most importantly Unity itself is working on a Dynamic lighting system, currently in beta (for 2019.2). Unity introduced the package Lightweight RP for 2d lights here and there's a tutorial here.