Simplex noise-based shader

kernel_generator_custom_simplex2.lua

--- An example shader that uses simplex noise.

--
-- 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.
--
-- [ MIT license: http://www.opensource.org/licenses/mit-license.php ]
--

local kernel = {}

kernel.language = "glsl"

kernel.category = "generator"

kernel.name = "simplex2"

kernel.isTimeDependent = true

-- Expose effect parameters using vertex data
kernel.vertexData =
{
	{
		name = "scale", -- The property name exposed to Lua
		default = 25, 
		min = 10,
		max = 100,
		index = 0, -- This corresponds to CoronaVertexUserData.x
	},

	{
		name = "speed", -- The property name exposed to Lua
		default = 2.7, 
		min = 0,
		max = 15,
		index = 1, -- This corresponds to CoronaVertexUserData.y
	},

	{
		name = "frequency", -- The property name exposed to Lua
		default = 1.3, 
		min = .2,
		max = 8,
		index = 2, -- This corresponds to CoronaVertexUserData.z
	},
}

kernel.fragment =
[[
	#ifdef GL_ES
		precision mediump float;
	#endif

// Uses 2D simplex noise from here: https://github.com/ashima/webgl-noise

vec3 mod289(vec3 x) {
  return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec2 mod289(vec2 x) {
  return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec3 permute(vec3 x) {
  return mod289(((x*34.0)+1.0)*x);
}

float snoise(vec2 v)
  {
  const vec4 C = vec4(0.211324865405187,  // (3.0-sqrt(3.0))/6.0
                      0.366025403784439,  // 0.5*(sqrt(3.0)-1.0)
                     -0.577350269189626,  // -1.0 + 2.0 * C.x
                      0.024390243902439); // 1.0 / 41.0
// First corner
  vec2 i  = floor(v + dot(v, C.yy) );
  vec2 x0 = v -   i + dot(i, C.xx);

// Other corners
  vec2 i1;
  //i1.x = step( x0.y, x0.x ); // x0.x > x0.y ? 1.0 : 0.0
  //i1.y = 1.0 - i1.x;
  i1 = (x0.x > x0.y) ? vec2(1.0, 0.0) : vec2(0.0, 1.0);
  // x0 = x0 - 0.0 + 0.0 * C.xx ;
  // x1 = x0 - i1 + 1.0 * C.xx ;
  // x2 = x0 - 1.0 + 2.0 * C.xx ;
  vec4 x12 = x0.xyxy + C.xxzz;
  x12.xy -= i1;

// Permutations
  i = mod289(i); // Avoid truncation effects in permutation
  vec3 p = permute( permute( i.y + vec3(0.0, i1.y, 1.0 ))
		+ i.x + vec3(0.0, i1.x, 1.0 ));

  vec3 m = max(0.5 - vec3(dot(x0,x0), dot(x12.xy,x12.xy), dot(x12.zw,x12.zw)), 0.0);
  m = m*m ;
  m = m*m ;

// Gradients: 41 points uniformly over a line, mapped onto a diamond.
// The ring size 17*17 = 289 is close to a multiple of 41 (41*7 = 287)

  vec3 x = 2.0 * fract(p * C.www) - 1.0;
  vec3 h = abs(x) - 0.5;
  vec3 ox = floor(x + 0.5);
  vec3 a0 = x - ox;

// Normalise gradients implicitly by scaling m
// Approximation of: m *= inversesqrt( a0*a0 + h*h );
  m *= 1.79284291400159 - 0.85373472095314 * ( a0*a0 + h*h );

// Compute final noise value at P
  vec3 g;
  g.x  = a0.x  * x0.x  + h.x  * x0.y;
  g.yz = a0.yz * x12.xz + h.yz * x12.yw;
  return 130.0 * dot(m, g);
}


P_COLOR vec4 FragmentKernel( P_UV vec2 texCoord )
{
	texCoord.xy *= CoronaVertexUserData.x; // scale 25.0
	texCoord.x += CoronaTotalTime * CoronaVertexUserData.y; // speed 2.7
	texCoord.y *= sin(CoronaTotalTime * CoronaVertexUserData.z); // frequency 1.3

	P_COLOR float sample = snoise(texCoord);

	return CoronaColorScale( vec4(sample, sample, sample, 1) );
}
]]

return kernel

main.lua

--- Driver for shader demo.

--
-- 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.
--
-- [ MIT license: http://www.opensource.org/licenses/mit-license.php ]
--

-- Setup
local widget = require( "widget" )

display.setStatusBar( display.HiddenStatusBar ) 

local image = display.newCircle(0, 0, 125)

image.x = display.contentCenterX
image.y = display.contentCenterY

------------------------------------------------------------

-- Debugging: 
-- Log compiler errors found in shader code to console
display.setDefault( 'isShaderCompilerVerbose', true )

-- Load custom filter
local kernel = require "kernel_generator_custom_simplex2"

graphics.defineEffect( kernel )

-- Apply filter
image.fill.effect = "generator.custom.simplex2"

------------------------------------------------------------

local function SliderAndText (top, prop, min_value, max_value)
	local range = max_value - min_value -- see the shader file for these values
	local slider = widget.newSlider{
		top = top, left = 10,
		orientation = "horizontal",
		value = 100 * (image.fill.effect[prop] - min_value) / range,
		listener = function(event)
			image.fill.effect[prop] = min_value + (event.value / 100) * range
		end
	}

	local text = display.newText(prop, 0, slider.y, native.systemFont, 20)

	text.anchorX, text.x = 0, slider.contentBounds.xMax + 10
end

-- Create scale, speed, frequency sliders
SliderAndText(10, "scale", 10, 100)
SliderAndText(40, "speed", 0, 15)
SliderAndText(70, "frequency", .2, 8)