1 files changed, 107 insertions, 0 deletions
diff --git a/libs/moonshine/godsray.lua b/libs/moonshine/godsray.lua
new file mode 100644
index 0000000..6c9f74a
--- /dev/null
+++ b/libs/moonshine/godsray.lua
@@ -0,0 +1,107 @@
+--[[
+The MIT License (MIT)
+
+Original code: Copyright (c) 2015 Josef Patoprsty
+Port to moonshine: Copyright (c) 2017 Matthias Richter <vrld@vrld.org>
+
+Based on work by: ioxu
+
+https://www.love2d.org/forums/viewtopic.php?f=4&t=3733&start=120#p71099
+
+Based on work by: Fabien Sanglard
+
+http://fabiensanglard.net/lightScattering/index.php
+
+Based on work from:
+
+[Mitchell]: Kenny Mitchell "Volumetric Light Scattering as a Post-Process" GPU Gems 3 (2005).
+[Mitchell2]: Jason Mitchell "Light Shaft Rendering" ShadersX3 (2004).
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+]]--
+
+return function(moonshine)
+  local shader = love.graphics.newShader[[
+    extern number exposure;
+    extern number decay;
+    extern number density;
+    extern number weight;
+    extern vec2 light_position;
+    extern number samples;
+
+    vec4 effect(vec4 color, Image tex, vec2 uv, vec2 px) {
+      color = Texel(tex, uv);
+
+      vec2 offset = (uv - light_position) * density / samples;
+      number illumination = decay;
+      vec4 c = vec4(.0, .0, .0, 1.0);
+
+      for (int i = 0; i < int(samples); ++i) {
+        uv -= offset;
+        c += Texel(tex, uv) * illumination * weight;
+        illumination *= decay;
+      }
+
+      return vec4(c.rgb * exposure + color.rgb, color.a);
+    }]]
+
+
+  local setters, light_position = {}
+
+  for _,k in ipairs{"exposure", "decay", "density", "weight"} do
+    setters[k] = function(v)
+      shader:send(k, math.min(1, math.max(0, tonumber(v) or 0)))
+    end
+  end
+
+  setters.light_position = function(v)
+    light_position = {unpack(v)}
+    shader:send("light_position", v)
+  end
+
+  setters.light_x = function(v)
+    assert(type(v) == "number", "Invalid value for `light_x'")
+    setters.light_position{v, light_position[2]}
+  end
+
+  setters.light_y = function(v)
+    assert(type(v) == "number", "Invalid value for `light_y'")
+    setters.light_position{light_position[1], v}
+  end
+
+  setters.samples = function(v)
+    shader:send("samples", math.max(1,tonumber(v) or 1))
+  end
+
+  local defaults = {
+    exposure = 0.25,
+    decay = 0.95,
+    density = 0.15,
+    weight = 0.5,
+    light_position = {0.5,0.5},
+    samples = 70
+  }
+
+  return moonshine.Effect{
+    name = "godsray",
+    shader = shader,
+    setters = setters,
+    defaults = defaults
+  }
+end