#!/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.

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

-- 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, 1, 0)
    local distance  = 4
    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 on the buddha
    return vec_new(2, 1, 2)
end

-- Define the actual objects of the scene that will be rendered, in the
-- extended u3d format.
local scene = [[
L 0 1000000 0 1 1 1 1 1 1
L 0 0 1000000 1 1 1 1 1 1
g triangle.raw
c 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
t 2 0 -2
s 1 1 1
g dragon.raw
M 0.3 0.3 0.3 5
c 0.7 0.3 0.2 0.8 0.2 0.1 0.9 0.2 0.2
t -2 -1 -2
s 2 2 2
g budda.raw
c 0.1 0.2 0.7 0.1 0.3 0.9 0.2 0.1 0.8
t 2 -1.5 2
s 10 10 10
g bunny.raw
M 0.2 0.2 0.2 1
c 0.9 0.8 0.9 0.8 0.7 0.9 0.9 0.8 0.7
t -2 -1 2
s 10 10 10
g teapot2.raw
M 1 1 1 128
c 0 1 0 0 1 0 0 1 0
t 0 -1 0
s 0.6 0.6 0.6
]]

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


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

local fmt   = string.format
local write = function(...) io.write(fmt(...)) end

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

function render(i)
    while i do
        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 + 1, frames)
        out:write(fmt([[
U3
%d %d
%f %f %f
%f %f %f
0 1 0
1.57 %f 0.1 1000
%s
X
]], size.w, size.h, e.x, e.y, e.z, l.x, l.y, l.z, size.w/size.h, scene))
        i = coroutine.yield()
        out:close()
    end
end

print("Animating scene...")

local threads = {}
for i = 1,jobs do
    table.insert(threads, coroutine.wrap(render))
end

os.execute("rm -rf frames && mkdir frames >/dev/null 2>&1")
for i = 0,(frames-1) do
    threads[1 + (i % jobs)](i)
end
for _,thread in ipairs(threads) do thread(null) end
print()

if os.execute("ffmpeg -i frames/anim%04d.bmp -b 1024k -y -an scene.avi") == 0 then
    print("Animation written to scene.avi.")
end