https://github.com/speakk/lighter

A Löve light/shadow library
https://github.com/speakk/lighter

dynamic-lighting lighting love2d love2d-framework

Last synced: about 2 months ago
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A Löve light/shadow library

• Host: GitHub
• URL: https://github.com/speakk/lighter
• Owner: speakk
• Created: 2020-11-12T22:22:13.000Z (about 4 years ago)
• Default Branch: master
• Last Pushed: 2023-09-02T05:42:17.000Z (over 1 year ago)
• Last Synced: 2024-10-01T08:03:18.398Z (2 months ago)
• Topics: dynamic-lighting, lighting, love2d, love2d-framework
• Language: Lua
• Homepage:
• Size: 177 KB
• Stars: 35
• Watchers: 3
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.md

Awesome Lists containing this project

• awesome-love2d - lighter - A performant dynamic light implementation with a simple API. (Lighting)

README

        
# Lighter

A dynamic light / shadow casting library for Löve.

## Installation

Clone the repo into your libs directory and require with 

    require 'path.to.lighter'

## Usage

    local Lighter = require 'path.to.lighter'

    local lighter = Lighter()

    local wall = {

        100, 100,

        300, 100,

        300, 300,

        100, 300

    }

    lighter:addPolygon(wall)

    local lightX, lightY = 500, 500

    -- addLight signature: (x,y,radius,r,g,b,a)

    local light = lighter:addLight(lightX, lightY, 500, 1, 0.5, 0.5)

    function love.update(dt)

        lightX, lightY = love.mouse.getPosition()

        lighter:updateLight(light, lightX, lightY)

    end

    function love.draw()

        love.graphics.polygon('fill', wall)

        lighter:drawLights()

    end

    -- Clean up

    -- lighter:removeLight(light)

    -- lighter:removePolygon(wall)

### How to use in your game context with a darker global illumination:

#### (remember you can use any combination of additive & multiplicative blending to achieve a result you like)

    -- Call after your light positions have been updated

    function preDrawLights()

      love.graphics.setCanvas({ lightCanvas, stencil = true})

      love.graphics.clear(0.4, 0.4, 0.4) -- Global illumination level

      self.lighter:drawLights()

      love.graphics.setCanvas()

    end

    

    -- Call after you have drawn your scene (but before UI)

    function drawLights()

      love.graphics.setBlendMode("multiply", "premultiplied")

      love.graphics.draw(lightCanvas)

      love.graphics.setBlendMode("alpha")

    end

### Function signatures of the public API:

```

    init = function(self, options)

    addLight = function(self, x, y, radius, r, g, b, a, gradientImage)

    updateLight = function(self, light, x, y, radius, r, g, b, a, gradientImage)

    removeLight = function(self, light)

    addPolygon = function(self, polygon)

    removePolygon = function(self, polygon)

    drawVisibilityPolygon = function(self, light)

    drawLights = function(self)

```

## Credits:

  * Helped me understand the premise and their code provided me with tons of helpful tips for getting this implemented: [https://github.com/OneLoneCoder](https://github.com/OneLoneCoder)

  * The actual page I ended up following to really get the idea: [https://ncase.me/sight-and-light/](https://ncase.me/sight-and-light/)

### Screenshot of the library in use in a game

![Screenshot of the library in use in a game](./screenshot.jpg)

## How it works under the hood

For each light we cast rays towards wall polygon corners (aka map features). Checks intersections.

Builds a visibility polygon and uses it as the stencil for drawing the light.

As an optimization it uses a spatial map and calculates polygon bounding boxes on the fly so that only polygons within light radius get included in the visibility polygon calculations.