#!/usr/bin/env lua

--
-- CS5600 University of Utah
-- Charles McGarvey
-- mcgarvey@eng.utah.edu
--

-- This program automates the process of creating simple fly-by animations.
-- The rasters are saved in the `frames' directory, and if ffmpeg is
-- installed, the frames will also be combined into a video file.  This script
-- must be called from the same directory where the rasterize program is.
-- The CACHE_GEOMETRY option is also recommended to improve performance.

-- Set the number of frames to be rendered for the animation.
local frames = 360

-- Define the code to calculate where the camera is, in world coordinates.
local eye = function(frame)
    -- just rotate around the center of the scene on the XZ plane
    local center    = vec_new(0, 0.4, 0)
    local distance  = 0.7
    local start     = math.pi
    local t = start + 2 * math.pi * frame / frames
    local v = vec_new(math.cos(t), 0, math.sin(t))
    return vec_add(vec_scale(v, distance), center)
end

-- Define the code to calculate where the focal point of the scene is.
local look = function(frame)
    -- keep the camera focused at the center
    return vec_new(0, 0, 0)
end

-- Define the actual objects of the scene that will be rendered, in the
-- extended u3d format.
local scene = [[
l -14687.0 7986.0 8976.0 1.0 1.0 1.0
g checker.obj
c 1.0 0.6 0.6 0.6
m checker.ppm
r -1.57 1.0 0.0 0.0
p 1.0 1.0 1.0 100.0
g teapot.raw
c 0.9 0.7 0.1 0.2
p 1.0 1.0 1.0 60.0
t 0.0 0.1 0.0
s 0.004 0.004 0.004
]]

-- Set the number of samples for supersampling.  If this is set to a value
-- of two or greater, each frame will be rendered larger by the factor
-- specified.  ImageMagick is used to scale the frames back down to size;
-- if ImageMagick is not installed, this script will exit with error 1.
local supersample = 2

-- Set the width and height of the viewport.
local size = {w = 640, h = 480}

-- Set the number of concurrent renderings (for multi-core machines).
local jobs = 6

-- Set the options to be passed directly to ffmpeg.
local ffmpeg_opts = "-b 1024k"

-- end of configuration
---------------------------------------------------------------------------

function vec_new(x, y, z)
    return {x = x, y = y, z = z}
end

function vec_add(a, b)
    return vec_new(a.x + b.x, a.y + b.y, a.z + b.z)
end

function vec_scale(v, s)
    return vec_new(v.x * s, v.y * s, v.z * s)
end

local fmt   = string.format
local write = function(...) io.write(fmt(...)) io.flush() end
local run   = function(...) return os.execute(fmt(...)) end

function render(i)
    while i do
        local w, h = size.w, size.h
        if 1 < supersample then
            w = w * supersample
            h = h * supersample
        end
        local filename  = fmt("frames/anim%04d.bmp", i)
        local command   = fmt("./rasterize -o %s >/dev/null", filename)
        local out = io.popen(command, "w")
        local e = eye(i)
        local l = look(i)
        write("\27[80D\27[2Kframe\t %4d / %d", i, frames)
        out:write(fmt([[
U4
%d %d
%f %f %f
%f %f %f
0 1 0
1.57 %f 0.1 1000
1.0 1.0 1.0
%s
X
]], w, h, e.x, e.y, e.z, l.x, l.y, l.z, size.w/size.h, scene))
        i = coroutine.yield()
        out:close()
        if 1 < supersample and
                not run("convert %s -scale %dx%d %s", filename, size.w, size.h, filename) then
            print()
            os.exit(1)
        end
    end
end

function renderings()
    local t = {}
    for i = 1,jobs do
        table.insert(t, coroutine.wrap(render))
    end
    local iterations = frames + jobs
    local frame = 0
    return function()
        frame = frame + 1
        if frame <= iterations then
            local i = frame
            if frames < i then i = null end
            return t[1 + frame % jobs], i
        end
    end
end

print("Animating scene...")

run("rm -rf frames && mkdir frames >/dev/null 2>&1")
for render,frame in renderings() do render(frame) end

print()

if run("ffmpeg -i frames/anim%%04d.bmp %s -y -an scene.avi", ffmpeg_opts) then
    print("Animation written to scene.avi.")
else
    print("The animation could not be created. Is ffmpeg installed?")
    os.exit(2)
end