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579 lines
13 KiB
V
579 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{v.y * b.z - v.z * b.y, v.z * b.x - v.x * b.z, v.x * b.y - v.y * b.x}
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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: unsafe { &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') or { panic(err) }
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f_out.writeln('$image.width $image.height') or { panic(err) }
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f_out.writeln('255') or { panic(err) }
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for i in 0 .. npixels {
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c_r := to_int(unsafe { image.data[i] }.x)
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c_g := to_int(unsafe { image.data[i] }.y)
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c_b := to_int(unsafe { image.data[i] }.z)
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f_out.write_string('$c_r $c_g $c_b ') or { panic(err) }
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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 */ Sphere{
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rad: 1e+5
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p: Vec{1e+5 + 1, 40.8, 81.6}
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e: Vec{}
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c: Vec{.75, .25, .25}
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refl: .diff
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}, /* Left */ Sphere{
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rad: 1e+5
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p: Vec{-1e+5 + 99, 40.8, 81.6}
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e: Vec{}
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c: Vec{.25, .25, .75}
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refl: .diff
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}, /* Rght */ Sphere{
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rad: 1e+5
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p: Vec{50, 40.8, 1e+5}
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e: Vec{}
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c: Vec{.75, .75, .75}
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refl: .diff
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}, /* Back */ Sphere{
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rad: 1e+5
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p: Vec{50, 40.8, -1e+5 + 170}
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e: Vec{}
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c: Vec{}
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refl: .diff
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}, /* Frnt */ Sphere{
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rad: 1e+5
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p: Vec{50, 1e+5, 81.6}
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e: Vec{}
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c: Vec{.75, .75, .75}
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refl: .diff
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}, /* Botm */ Sphere{
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rad: 1e+5
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p: Vec{50, -1e+5 + 81.6, 81.6}
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e: Vec{}
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c: Vec{.75, .75, .75}
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refl: .diff
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}, /* Top */ Sphere{
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rad: 16.5
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p: Vec{27, 16.5, 47}
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e: Vec{}
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c: Vec{1, 1, 1}.mult_s(.999)
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refl: .spec
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}, /* Mirr */ Sphere{
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rad: 16.5
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p: Vec{73, 16.5, 78}
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e: Vec{}
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c: Vec{1, 1, 1}.mult_s(.999)
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refl: .refr
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}, /* Glas */ Sphere{
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rad: 600
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p: Vec{50, 681.6 - .27, 81.6}
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e: Vec{12, 12, 12}
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c: Vec{}
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refl: .diff
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} /* Lite */],
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[/* scene 1 sunset */ Sphere{
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rad: 1600
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p: Vec{1.0, 0.0, 2.0}.mult_s(3000)
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e: Vec{1.0, .9, .8}.mult_s(1.2e+1 * 1.56 * 2)
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c: Vec{}
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refl: .diff
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}, /* sun */ Sphere{
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rad: 1560
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p: Vec{1, 0, 2}.mult_s(3500)
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e: Vec{1.0, .5, .05}.mult_s(4.8e+1 * 1.56 * 2)
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c: Vec{}
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refl: .diff
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}, /* horizon sun2 */ Sphere{
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rad: 10000
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p: cen + Vec{0, 0, -200}
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e: Vec{0.00063842, 0.02001478, 0.28923243}.mult_s(6e-2 * 8)
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c: Vec{.7, .7, 1}.mult_s(.25)
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refl: .diff
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}, /* sky */ Sphere{
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rad: 100000
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p: Vec{50, -100000, 0}
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e: Vec{}
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c: Vec{.3, .3, .3}
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refl: .diff
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}, /* grnd */ Sphere{
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rad: 110000
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p: Vec{50, -110048.5, 0}
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e: Vec{.9, .5, .05}.mult_s(4)
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c: Vec{}
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refl: .diff
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}, /* horizon brightener */ Sphere{
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rad: 4e+4
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p: Vec{50, -4e+4 - 30, -3000}
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e: Vec{}
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c: Vec{.2, .2, .2}
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refl: .diff
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}, /* mountains */ Sphere{
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rad: 26.5
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p: Vec{22, 26.5, 42}
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e: Vec{}
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c: Vec{1, 1, 1}.mult_s(.596)
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refl: .spec
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}, /* white Mirr */ Sphere{
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rad: 13
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p: Vec{75, 13, 82}
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e: Vec{}
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c: Vec{.96, .96, .96}.mult_s(.96)
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refl: .refr
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}, /* Glas */ Sphere{
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rad: 22
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p: Vec{87, 22, 24}
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e: Vec{}
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c: Vec{.6, .6, .6}.mult_s(.696)
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refl: .refr
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} /* Glas2 */],
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[/* scene 3 Psychedelic */ Sphere{
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rad: 150
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p: Vec{50 + 75, 28, 62}
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e: Vec{1, 1, 1}.mult_s(0e-3)
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c: Vec{1, .9, .8}.mult_s(.93)
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refl: .refr
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}, Sphere{
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rad: 28
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p: Vec{50 + 5, -28, 62}
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e: Vec{1, 1, 1}.mult_s(1e+1)
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c: Vec{1, 1, 1}.mult_s(0)
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refl: .diff
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}, Sphere{
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rad: 300
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p: Vec{50, 28, 62}
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e: Vec{1, 1, 1}.mult_s(0e-3)
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c: Vec{1, 1, 1}.mult_s(.93)
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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 {
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return 0
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}
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if x > 1 {
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return 1
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}
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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 {
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return Vec{}
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}
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// 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) { Vec{0, 1, 0} } else { Vec{1, 0, 0} }
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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) +
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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)) +
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(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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|
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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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|
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// 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 := 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()
|
|
|
|
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')
|
|
}
|