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v/examples/path_tracing.v

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V

/**********************************************************************
* path tracing demo
*
* Copyright (c) 2019-2021 Dario Deledda. All rights reserved.
* Use of this source code is governed by an MIT license
* that can be found in the LICENSE file.
*
* This file contains a path tracer example in less of 500 line of codes
* 3 demo scenes included
*
* This code is inspired by:
* - "Realistic Ray Tracing" by Peter Shirley 2000 ISBN-13: 978-1568814612
* - https://www.kevinbeason.com/smallpt/
*
* Known limitations:
* - there are some approximation errors in the calculations
* - to speed-up the code a cos/sin table is used
* - the full precision code is present but commented, can be restored very easily
* - an higher number of samples ( > 60) can block the program on higher resolutions
* without a stack size increase
* - as a recursive program this code depend on the stack size,
* for higher number of samples increase the stack size
* in linux: ulimit -s byte_size_of_the_stack
* example: ulimit -s 16000000
* - No OpenMP support
**********************************************************************/
import os
import math
import rand
import time
import term
const (
inf = 1e+10
eps = 1e-4
f_0 = 0.0
)
//**************************** 3D Vector utility struct *********************
struct Vec {
mut:
x f64 = 0.0
y f64 = 0.0
z f64 = 0.0
}
[inline]
fn (v Vec) + (b Vec) Vec {
return Vec{v.x + b.x, v.y + b.y, v.z + b.z}
}
[inline]
fn (v Vec) - (b Vec) Vec {
return Vec{v.x - b.x, v.y - b.y, v.z - b.z}
}
[inline]
fn (v Vec) * (b Vec) Vec {
return Vec{v.x * b.x, v.y * b.y, v.z * b.z}
}
[inline]
fn (v Vec) dot(b Vec) f64 {
return v.x * b.x + v.y * b.y + v.z * b.z
}
[inline]
fn (v Vec) mult_s(b f64) Vec {
return Vec{v.x * b, v.y * b, v.z * b}
}
[inline]
fn (v Vec) cross(b Vec) Vec {
return Vec{v.y * b.z - v.z * b.y, v.z * b.x - v.x * b.z, v.x * b.y - v.y * b.x}
}
[inline]
fn (v Vec) norm() Vec {
tmp_norm := 1.0 / math.sqrt(v.x * v.x + v.y * v.y + v.z * v.z)
return Vec{v.x * tmp_norm, v.y * tmp_norm, v.z * tmp_norm}
}
//********************************Image**************************************
struct Image {
width int
height int
data &Vec
}
fn new_image(w int, h int) Image {
vecsize := int(sizeof(Vec))
return Image{
width: w
height: h
data: unsafe { &Vec(vcalloc(vecsize * w * h)) }
}
}
// write out a .ppm file
fn (image Image) save_as_ppm(file_name string) {
npixels := image.width * image.height
mut f_out := os.create(file_name) or { panic(err) }
f_out.writeln('P3') or { panic(err) }
f_out.writeln('$image.width $image.height') or { panic(err) }
f_out.writeln('255') or { panic(err) }
for i in 0 .. npixels {
c_r := to_int(unsafe { image.data[i] }.x)
c_g := to_int(unsafe { image.data[i] }.y)
c_b := to_int(unsafe { image.data[i] }.z)
f_out.write_string('$c_r $c_g $c_b ') or { panic(err) }
}
f_out.close()
}
//********************************** Ray ************************************
struct Ray {
o Vec
d Vec
}
// material types, used in radiance()
enum Refl_t {
diff
spec
refr
}
//******************************** Sphere ***********************************
struct Sphere {
rad f64 = 0.0 // radius
p Vec // position
e Vec // emission
c Vec // color
refl Refl_t // reflection type => [diffuse, specular, refractive]
}
fn (sp Sphere) intersect(r Ray) f64 {
op := sp.p - r.o // Solve t^2*d.d + 2*t*(o-p).d + (o-p).(o-p)-R^2 = 0
b := op.dot(r.d)
mut det := b * b - op.dot(op) + sp.rad * sp.rad
if det < 0 {
return 0
}
det = math.sqrt(det)
mut t := b - det
if t > eps {
return t
}
t = b + det
if t > eps {
return t
}
return 0
}
/*********************************** Scenes **********************************
* 0) Cornell Box with 2 spheres
* 1) Sunset
* 2) Psychedelic
* The sphere fileds are: Sphere{radius, position, emission, color, material}
******************************************************************************/
const (
cen = Vec{50, 40.8, -860} // used by scene 1
spheres = [
[// scene 0 cornnel box
Sphere{
rad: 1e+5
p: Vec{1e+5 + 1, 40.8, 81.6}
e: Vec{}
c: Vec{.75, .25, .25}
refl: .diff
}, /* Left */
Sphere{
rad: 1e+5
p: Vec{-1e+5 + 99, 40.8, 81.6}
e: Vec{}
c: Vec{.25, .25, .75}
refl: .diff
}, /* Rght */
Sphere{
rad: 1e+5
p: Vec{50, 40.8, 1e+5}
e: Vec{}
c: Vec{.75, .75, .75}
refl: .diff
}, /* Back */
Sphere{
rad: 1e+5
p: Vec{50, 40.8, -1e+5 + 170}
e: Vec{}
c: Vec{}
refl: .diff
}, /* Frnt */
Sphere{
rad: 1e+5
p: Vec{50, 1e+5, 81.6}
e: Vec{}
c: Vec{.75, .75, .75}
refl: .diff
}, /* Botm */
Sphere{
rad: 1e+5
p: Vec{50, -1e+5 + 81.6, 81.6}
e: Vec{}
c: Vec{.75, .75, .75}
refl: .diff
}, /* Top */
Sphere{
rad: 16.5
p: Vec{27, 16.5, 47}
e: Vec{}
c: Vec{1, 1, 1}.mult_s(.999)
refl: .spec
}, /* Mirr */
Sphere{
rad: 16.5
p: Vec{73, 16.5, 78}
e: Vec{}
c: Vec{1, 1, 1}.mult_s(.999)
refl: .refr
}, /* Glas */
Sphere{
rad: 600
p: Vec{50, 681.6 - .27, 81.6}
e: Vec{12, 12, 12}
c: Vec{}
refl: .diff
} /* Lite */,
],
[// scene 1 sunset
Sphere{
rad: 1600
p: Vec{1.0, 0.0, 2.0}.mult_s(3000)
e: Vec{1.0, .9, .8}.mult_s(1.2e+1 * 1.56 * 2)
c: Vec{}
refl: .diff
}, /* sun */
Sphere{
rad: 1560
p: Vec{1, 0, 2}.mult_s(3500)
e: Vec{1.0, .5, .05}.mult_s(4.8e+1 * 1.56 * 2)
c: Vec{}
refl: .diff
}, /* horizon sun2 */
Sphere{
rad: 10000
p: cen + Vec{0, 0, -200}
e: Vec{0.00063842, 0.02001478, 0.28923243}.mult_s(6e-2 * 8)
c: Vec{.7, .7, 1}.mult_s(.25)
refl: .diff
}, /* sky */
Sphere{
rad: 100000
p: Vec{50, -100000, 0}
e: Vec{}
c: Vec{.3, .3, .3}
refl: .diff
}, /* grnd */
Sphere{
rad: 110000
p: Vec{50, -110048.5, 0}
e: Vec{.9, .5, .05}.mult_s(4)
c: Vec{}
refl: .diff
}, /* horizon brightener */
Sphere{
rad: 4e+4
p: Vec{50, -4e+4 - 30, -3000}
e: Vec{}
c: Vec{.2, .2, .2}
refl: .diff
}, /* mountains */
Sphere{
rad: 26.5
p: Vec{22, 26.5, 42}
e: Vec{}
c: Vec{1, 1, 1}.mult_s(.596)
refl: .spec
}, /* white Mirr */
Sphere{
rad: 13
p: Vec{75, 13, 82}
e: Vec{}
c: Vec{.96, .96, .96}.mult_s(.96)
refl: .refr
}, /* Glas */
Sphere{
rad: 22
p: Vec{87, 22, 24}
e: Vec{}
c: Vec{.6, .6, .6}.mult_s(.696)
refl: .refr
} /* Glas2 */,
],
[// scene 3 Psychedelic
Sphere{
rad: 150
p: Vec{50 + 75, 28, 62}
e: Vec{1, 1, 1}.mult_s(0e-3)
c: Vec{1, .9, .8}.mult_s(.93)
refl: .refr
},
Sphere{
rad: 28
p: Vec{50 + 5, -28, 62}
e: Vec{1, 1, 1}.mult_s(1e+1)
c: Vec{1, 1, 1}.mult_s(0)
refl: .diff
},
Sphere{
rad: 300
p: Vec{50, 28, 62}
e: Vec{1, 1, 1}.mult_s(0e-3)
c: Vec{1, 1, 1}.mult_s(.93)
refl: .spec
},
],
] // end of scene array
)
//********************************** Utilities ******************************
[inline]
fn clamp(x f64) f64 {
if x < 0 {
return 0
}
if x > 1 {
return 1
}
return x
}
[inline]
fn to_int(x f64) int {
p := math.pow(clamp(x), 1.0 / 2.2)
return int(p * 255.0 + 0.5)
}
fn intersect(r Ray, spheres &Sphere, nspheres int) (bool, f64, int) {
mut d := 0.0
mut t := inf
mut id := 0
for i := nspheres - 1; i >= 0; i-- {
d = unsafe { spheres[i] }.intersect(r)
if d > 0 && d < t {
t = d
id = i
}
}
return t < inf, t, id
}
// some casual random function, try to avoid the 0
fn rand_f64() f64 {
x := rand.u32() & 0x3FFF_FFFF
return f64(x) / f64(0x3FFF_FFFF)
}
const (
cache_len = 65536 // the 2*pi angle will be splitted in 65536 part
cache_mask = cache_len - 1 // mask to speed-up the module process
)
struct Cache {
mut:
sin_tab [65536]f64
cos_tab [65536]f64
}
fn new_tabs() Cache {
mut c := Cache{}
inv_len := 1.0 / f64(cache_len)
for i in 0 .. cache_len {
x := f64(i) * math.pi * 2.0 * inv_len
c.sin_tab[i] = math.sin(x)
c.cos_tab[i] = math.cos(x)
}
return c
}
//************ Cache for sin/cos speed-up table and scene selector **********
const (
tabs = new_tabs()
)
//****************** main function for the radiance calculation *************
fn radiance(r Ray, depthi int, scene_id int) Vec {
if depthi > 1024 {
eprintln('depthi: $depthi')
eprintln('')
return Vec{}
}
mut depth := depthi // actual depth in the reflection tree
mut t := 0.0 // distance to intersection
mut id := 0 // id of intersected object
mut res := false // result of intersect
v_1 := 1.0
// v_2 := f64(2.0)
scene := spheres[scene_id]
// res, t, id = intersect(r, id, tb.scene)
res, t, id = intersect(r, scene.data, scene.len)
if !res {
return Vec{}
}
// if miss, return black
obj := scene[id] // the hit object
x := r.o + r.d.mult_s(t)
n := (x - obj.p).norm()
nl := if n.dot(r.d) < 0.0 { n } else { n.mult_s(-1) }
mut f := obj.c
// max reflection
mut p := f.z
if f.x > f.y && f.x > f.z {
p = f.x
} else {
if f.y > f.z {
p = f.y
}
}
depth++
if depth > 5 {
if rand_f64() < p {
f = f.mult_s(f64(1.0) / p)
} else {
return obj.e // R.R.
}
}
if obj.refl == .diff { // Ideal DIFFUSE reflection
// **Full Precision**
// r1 := f64(2.0 * math.pi) * rand_f64()
// tabbed speed-up
r1 := rand.u32() & cache_mask
r2 := rand_f64()
r2s := math.sqrt(r2)
w := nl
mut u := if math.abs(w.x) > f64(0.1) { Vec{0, 1, 0} } else { Vec{1, 0, 0} }
u = u.cross(w).norm()
v := w.cross(u)
// **Full Precision**
// d := (u.mult_s(math.cos(r1) * r2s) + v.mult_s(math.sin(r1) * r2s) + w.mult_s(1.0 - r2)).norm()
// tabbed speed-up
d := (u.mult_s(tabs.cos_tab[r1] * r2s) + v.mult_s(tabs.sin_tab[r1] * r2s) +
w.mult_s(math.sqrt(f64(1.0) - r2))).norm()
return obj.e + f * radiance(Ray{x, d}, depth, scene_id)
} else {
if obj.refl == .spec { // Ideal SPECULAR reflection
return obj.e + f * radiance(Ray{x, r.d - n.mult_s(2.0 * n.dot(r.d))}, depth, scene_id)
}
}
refl_ray := Ray{x, r.d - n.mult_s(2.0 * n.dot(r.d))} // Ideal dielectric REFRACTION
into := n.dot(nl) > 0 // Ray from outside going in?
nc := f64(1.0)
nt := f64(1.5)
nnt := if into { nc / nt } else { nt / nc }
ddn := r.d.dot(nl)
cos2t := v_1 - nnt * nnt * (v_1 - ddn * ddn)
if cos2t < 0.0 { // Total internal reflection
return obj.e + f * radiance(refl_ray, depth, scene_id)
}
dirc := if into { f64(1) } else { f64(-1) }
tdir := (r.d.mult_s(nnt) - n.mult_s(dirc * (ddn * nnt + math.sqrt(cos2t)))).norm()
a := nt - nc
b := nt + nc
r0 := a * a / (b * b)
c := if into { v_1 + ddn } else { v_1 - tdir.dot(n) }
re := r0 + (v_1 - r0) * c * c * c * c * c
tr := v_1 - re
pp := f64(.25) + f64(.5) * re
rp := re / pp
tp := tr / (v_1 - pp)
mut tmp := Vec{}
if depth > 2 {
// Russian roulette
tmp = if rand_f64() < pp {
radiance(refl_ray, depth, scene_id).mult_s(rp)
} else {
radiance(Ray{x, tdir}, depth, scene_id).mult_s(tp)
}
} else {
tmp = (radiance(refl_ray, depth, scene_id).mult_s(re)) +
(radiance(Ray{x, tdir}, depth, scene_id).mult_s(tr))
}
return obj.e + (f * tmp)
}
//*********************** beam scan routine *********************************
fn ray_trace(w int, h int, samps int, file_name string, scene_id int) Image {
image := new_image(w, h)
// inverse costants
w1 := f64(1.0 / f64(w))
h1 := f64(1.0 / f64(h))
samps1 := f64(1.0 / f64(samps))
cam := Ray{Vec{50, 52, 295.6}, Vec{0, -0.042612, -1}.norm()} // cam position, direction
cx := Vec{f64(w) * 0.5135 / f64(h), 0, 0}
cy := cx.cross(cam.d).norm().mult_s(0.5135)
mut r := Vec{}
// speed-up constants
v_1 := f64(1.0)
v_2 := f64(2.0)
// OpenMP injection point! #pragma omp parallel for schedule(dynamic, 1) shared(c)
for y := 0; y < h; y++ {
if y & 7 == 0 || y + 1 == h {
term.cursor_up(1)
eprintln('Rendering (${samps * 4} spp) ${(100.0 * f64(y)) / (f64(h) - 1.0):5.2f}%')
}
for x in 0 .. w {
i := (h - y - 1) * w + x
mut ivec := unsafe { &image.data[i] }
// we use sx and sy to perform a square subsampling of 4 samples
for sy := 0; sy < 2; sy++ {
for sx := 0; sx < 2; sx++ {
r = Vec{0, 0, 0}
for _ in 0 .. samps {
r1 := v_2 * rand_f64()
dx := if r1 < v_1 { math.sqrt(r1) - v_1 } else { v_1 - math.sqrt(v_2 - r1) }
r2 := v_2 * rand_f64()
dy := if r2 < v_1 { math.sqrt(r2) - v_1 } else { v_1 - math.sqrt(v_2 - r2) }
d := cx.mult_s(((f64(sx) + 0.5 + dx) * 0.5 + f64(x)) * w1 - .5) +
cy.mult_s(((f64(sy) + 0.5 + dy) * 0.5 + f64(y)) * h1 - .5) + cam.d
r = r + radiance(Ray{cam.o +
d.mult_s(140.0), d.norm()}, 0, scene_id).mult_s(samps1)
}
tmp_vec := Vec{clamp(r.x), clamp(r.y), clamp(r.z)}.mult_s(.25)
(*ivec) = *ivec + tmp_vec
}
}
}
}
return image
}
fn main() {
if os.args.len > 6 {
eprintln('Usage:\n path_tracing [samples] [image.ppm] [scene_n] [width] [height]')
exit(1)
}
mut width := 320 // width of the rendering in pixels
mut height := 200 // height of the rendering in pixels
mut samples := 4 // number of samples per pixel, increase for better quality
mut scene_id := 0 // scene to render [0 cornell box,1 sunset,2 psyco]
mut file_name := 'image.ppm' // name of the output file in .ppm format
if os.args.len >= 2 {
samples = os.args[1].int() / 4
}
if os.args.len >= 3 {
file_name = os.args[2]
}
if os.args.len >= 4 {
scene_id = os.args[3].int()
}
if os.args.len >= 5 {
width = os.args[4].int()
}
if os.args.len == 6 {
height = os.args[5].int()
}
// change the seed for a different result
rand.seed([u32(2020), 0])
t1 := time.ticks()
eprintln('Path tracing samples: $samples, file_name: $file_name, scene_id: $scene_id, width: $width, height: $height')
eprintln('')
image := ray_trace(width, height, samples, file_name, scene_id)
t2 := time.ticks()
eprintln('Rendering finished. Took: ${(t2 - t1):5}ms')
image.save_as_ppm(file_name)
t3 := time.ticks()
eprintln('Image saved as [$file_name]. Took: ${(t3 - t2):5}ms')
}