105 lines
3.4 KiB
Lua
105 lines
3.4 KiB
Lua
--[[
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Public domain:
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Copyright (C) 2017 by Matthias Richter <vrld@vrld.org>
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Permission to use, copy, modify, and/or distribute this software for any
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purpose with or without fee is hereby granted.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
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REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
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INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
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OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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PERFORMANCE OF THIS SOFTWARE.
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]]--
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-- unroll convolution loop for gaussian blur shader
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local function make_blur_shader(sigma)
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local support = math.max(1, math.floor(3*sigma + .5))
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local one_by_sigma_sq = sigma > 0 and 1 / (sigma * sigma) or 1
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local norm = 0
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local code = {[[
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extern vec2 direction;
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vec4 effect(vec4 color, Image texture, vec2 tc, vec2 _) {
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vec4 c = vec4(0.0);
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]]}
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local blur_line = "c += vec4(%f) * Texel(texture, tc + vec2(%f) * direction);"
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for i = -support,support do
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local coeff = math.exp(-.5 * i*i * one_by_sigma_sq)
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norm = norm + coeff
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code[#code+1] = blur_line:format(coeff, i)
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end
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code[#code+1] = ("return c * vec4(%f) * color;}"):format(1 / norm)
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return love.graphics.newShader(table.concat(code))
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end
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return function(moonshine)
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local blurshader -- set in setters.glow_strength
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local threshold = love.graphics.newShader[[
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extern number min_luma;
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vec4 effect(vec4 color, Image texture, vec2 tc, vec2 _) {
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vec4 c = Texel(texture, tc);
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number luma = dot(vec3(0.299, 0.587, 0.114), c.rgb);
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return c * step(min_luma, luma) * color;
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}]]
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local setters = {}
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setters.strength = function(v)
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blurshader = make_blur_shader(math.max(0,tonumber(v) or 1))
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end
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setters.min_luma = function(v)
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threshold:send("min_luma", math.max(0, math.min(1, tonumber(v) or 0.5)))
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end
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local scene = love.graphics.newCanvas()
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local draw = function(buffer)
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local front, back = buffer() -- scene so far is in `back'
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scene, back = back, scene -- save it for second draw below
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-- 1st pass: draw scene with brightness threshold
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love.graphics.setCanvas(front)
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love.graphics.clear()
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love.graphics.setShader(threshold)
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love.graphics.draw(scene)
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-- 2nd pass: apply blur shader in x
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blurshader:send('direction', {1 / love.graphics.getWidth(), 0})
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love.graphics.setCanvas(back)
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love.graphics.clear()
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love.graphics.setShader(blurshader)
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love.graphics.draw(front)
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-- 3nd pass: apply blur shader in y and draw original and blurred scene
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love.graphics.setCanvas(front)
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love.graphics.clear()
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-- original scene without blur shader
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love.graphics.setShader()
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love.graphics.setBlendMode("add", "premultiplied")
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love.graphics.draw(scene) -- original scene
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-- second pass of light blurring
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blurshader:send('direction', {0, 1 / love.graphics.getHeight()})
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love.graphics.setShader(blurshader)
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love.graphics.draw(back)
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-- restore things as they were before entering draw()
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love.graphics.setBlendMode("alpha", "premultiplied")
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scene = back
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end
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return moonshine.Effect{
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name = "glow",
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draw = draw,
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setters = setters,
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defaults = {min_luma=.7, strength = 5}
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}
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end
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