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v/examples/path_tracing.v

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V

/**********************************************************************
* path tracing demo
*
* Copyright (c) 2019-2020 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
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: &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')
f_out.writeln('${image.width} ${image.height}')
f_out.writeln('255')
for i in 0..npixels {
c_r := to_int(image.data[i].x)
c_g := to_int(image.data[i].y)
c_b := to_int(image.data[i].z)
f_out.write('$c_r $c_g $c_b ')
}
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 = 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')
return Vec{}
}
sin_tab := &f64( tabs.sin_tab )
cos_tab := &f64( tabs.cos_tab )
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(cos_tab[r1] * r2s) + v.mult_s(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++ {
eprint("\rRendering (${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 := &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()
image := ray_trace(width, height, samples, file_name, scene_id)
t2:=time.ticks()
eprintln('\nRendering 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')
}