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