strange_attractor_renderer/lib.rs
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//! Master branch online documentation is available at
//! [doc.icelk.dev](https://doc.icelk.dev/strange-attractor-renderer/strange_attractor_renderer/).
//!
//! # Pipeline
//!
//! First you need to get a [`Config`].
//! I suggest creating it like this:
//!
//! ```
//! # use strange_attractor_renderer::*;
//! let config = Config {
//! iterations: 100_000_000,
//! ..Config::poisson_saturne()
//! };
//! ```
//!
//! ## Multithreaded
//!
//! Call [`render_parallel`].
//!
//! This benefits the most when the number of iterations is much higher than the dimensions of the
//! image. The gap closes rapidly when the relation is < 25. This also consumes more memory, as we
//! need a set of working images for each execution unit, usually the number of threads on your
//! CPU. See [Performance](#performance) for more info.
//!
//! ## Single-threaded
//!
//! Create a [`Runtime`].
//! Then [`render`] and finally [`colorize`].
//!
//! # Performance
//!
//! The thing slowing the algorithm down with larger image dimensions
//! is the cache size - and memory access. We basically do random access reads and writes on a
//! often > 2 megapixel image. If the system memory is slow, this brings performance to a halt.
//!
//! # Colouring
//!
//! When the iterations are executed, the magnitude of change is stored in a texture. When it's
//! time for colouring, this |Δp| is mapped to a palette. The brightness is determined by the number
//! of visits to the pixel.
// there are many #[allow()] in the code. These disregard the lint warnings I've enabled below.
// some online documentation wizardry
#![cfg_attr(docsrs, feature(doc_auto_cfg))]
// deny all lints for the whole project, even the pedantic ones... :(
#![deny(clippy::all, clippy::pedantic)]
// allow the inline_always lint for the whole project, as they are heavily used to increase
// performance.
#![allow(clippy::inline_always)]
use std::fmt::Debug;
// import standard library items
use std::mem;
use std::sync::atomic::AtomicUsize;
use std::sync::{atomic, mpsc, Arc, Mutex};
use std::thread::JoinHandle;
// import items from external libraries
// image handles image formats and provide the main image type we use
use image::{GenericImage, GenericImageView, ImageBuffer, Luma, Pixel, Rgb, Rgba};
// used to get random initial points.
use rand::{Rng, SeedableRng};
pub use config::{ColorTransform, Colors, Config, RenderKind, View};
pub use primitives::{EulerAxisRotation, FloatExt, Vec3};
/// A strange attractor.
///
/// This is made generic to allow for speedy execution of all kinds of attractors.
pub trait Attractor: Debug + Clone {
/// Get the next point of the attractor.
///
/// Please make this `#[inline(always)]`!
#[must_use]
fn next_point(&self, previous: Vec3) -> Vec3;
}
/// Mathematical primitives
pub mod primitives {
use super::Rng;
use std::ops::{Add, Index, Mul, Sub};
/// Trait to use the following functions on the float primitives.
///
/// Here for convenience.
pub trait FloatExt {
#[must_use]
fn square(self) -> Self;
#[must_use]
fn lerp(self, other: Self, t: Self) -> Self;
}
impl FloatExt for f64 {
#[inline(always)]
fn square(self) -> Self {
self * self
}
#[inline(always)]
fn lerp(self, other: Self, t: Self) -> Self {
self * t + other * (1. - t)
}
}
impl FloatExt for f32 {
#[inline(always)]
fn square(self) -> Self {
self * self
}
#[inline(always)]
fn lerp(self, other: Self, t: Self) -> Self {
self * t + other * (1. - t)
}
}
#[derive(Debug, PartialEq, Clone, Copy)]
pub struct Vec3 {
pub x: f64,
pub y: f64,
pub z: f64,
}
impl Vec3 {
#[must_use]
pub fn new(x: f64, y: f64, z: f64) -> Self {
Self { x, y, z }
}
/// Length of this vector.
#[must_use]
#[inline(always)]
pub fn magnitude(self) -> f64 {
(self.x.square() + self.y.square() + self.z.square()).sqrt()
}
#[must_use]
#[inline(always)]
pub fn normalize(self) -> Self {
self * (1. / self.magnitude())
}
}
// implement operations for Vec3
impl Sub for Vec3 {
type Output = Self;
#[inline(always)]
fn sub(self, rhs: Self) -> Self::Output {
Self::new(self.x - rhs.x, self.y - rhs.y, self.z - rhs.z)
}
}
impl Add for Vec3 {
type Output = Self;
#[inline(always)]
fn add(self, rhs: Self) -> Self::Output {
Self::new(self.x - rhs.x, self.y - rhs.y, self.z - rhs.z)
}
}
impl Mul<f64> for Vec3 {
type Output = Self;
#[inline(always)]
fn mul(self, v: f64) -> Self::Output {
Self::new(self.x * v, self.y * v, self.z * v)
}
}
/// enables using `rng.gen` to get a Vec3, with x,y,z between 0 and 1
impl rand::distr::Distribution<Vec3> for rand::distr::StandardUniform {
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Vec3 {
let values: [f64; 3] = rng.random();
Vec3::new(values[0], values[1], values[2])
}
}
/// See [Wikipedia](https://en.wikipedia.org/wiki/Euler's_rotation_theorem) for more info.
#[derive(Debug, PartialEq, Clone, Copy)]
pub struct EulerAxisRotation {
/// The Euler axis
pub axis: Vec3,
/// Rotation around [`Self::axis`], in radians.
pub rotation: f64,
}
impl EulerAxisRotation {
#[must_use]
#[inline(always)]
pub fn to_rotation_matrix(self) -> Matrix3x3 {
let Self { axis, rotation } = self;
// normalize Vec, only on non-release/production builds, as this lowers performance
#[cfg(debug_assertions)]
let axis = axis.normalize();
let Vec3 { x, y, z } = axis;
let c = rotation.cos();
let c1 = 1. - c;
let s = rotation.sin();
Matrix3x3 {
columns: [
[c + x * x * c1, x * y * c1 - z * s, x * z * c1 + y * s],
[y * x * c1 + z * s, c + y * y * c1, y * z * c1 - x * s],
[z * x * c1 - y * s, z * y * c1 + x * s, c + z * z * c1],
],
}
}
}
/// A 3x3 matrix. Use `matrix[(0,2)]` to get the third item in the first column - indices are
/// zero-based.
#[derive(Debug, PartialEq, Clone)]
pub struct Matrix3x3 {
/// Each column contains a row with three [`f64`]s.
pub columns: [[f64; 3]; 3],
}
impl Matrix3x3 {
#[must_use]
#[inline(always)]
pub fn mul_right(&self, vec: Vec3) -> Vec3 {
let m = self.columns;
Vec3 {
x: m[0][0] * vec.x + m[0][1] * vec.y + m[0][2] * vec.z,
y: m[1][0] * vec.x + m[1][1] * vec.y + m[1][2] * vec.z,
z: m[2][0] * vec.x + m[2][1] * vec.y + m[2][2] * vec.z,
}
}
}
impl Index<(usize, usize)> for Matrix3x3 {
type Output = f64;
#[inline(always)]
fn index(&self, index: (usize, usize)) -> &Self::Output {
&self.columns[index.0][index.1]
}
}
}
/// Configuration for rendering - how to get the next iteration, colouring, camera position,
/// brightness, etc.
pub mod config {
use super::{attractors, Attractor, EulerAxisRotation, Rgb, Vec3};
use std::fmt::Debug;
/// How to render the internal data.
#[derive(Debug, Clone)]
pub enum RenderKind {
/// The default, creates a good-looking gas-like image.
Gas,
/// Renders the depth map.
Depth,
}
pub trait ColorTransform: Clone + Send + Sync + 'static {
/// Please set the attribute `#[inline(always)]`.
fn transform(&self, delta: Vec3, screen_space: Vec3, view: &View) -> f64;
}
impl<F: Fn(Vec3, Vec3, &View) -> f64 + Clone + Send + Sync + 'static> ColorTransform for F {
fn transform(&self, delta: Vec3, screen_space: Vec3, view: &View) -> f64 {
self(delta, screen_space, view)
}
}
/// Other data which is dependant on the [`Attractor`].
#[derive(Clone, Debug)]
pub struct View {
/// The position to center the camera on
///
/// Is highly related to which coefficients are chosen
pub center_camera: Vec3,
pub rotation: EulerAxisRotation,
/// General viewing scale. Increase this to zoom in more.
pub scale: f64,
}
#[derive(Clone, Debug)]
#[must_use]
pub struct Config<A: Attractor, T: ColorTransform> {
/// Heavily affects performance
pub iterations: usize,
/// Image width, slight performance decrease
pub width: u32,
/// Image height, slight performance decrease
pub height: u32,
pub render: RenderKind,
/// This reduces colour quality.
pub transparent: bool,
/// The camera rotation angle.
pub angle: f64,
/// Be less verbose.
pub silent: bool,
pub attractor: A,
pub colors: Colors,
pub view: View,
pub color_transform: T,
}
impl<A: Attractor, T: ColorTransform> Config<A, T> {
pub fn new(coefficients: A, view: View, transform_colors: T) -> Self {
Self {
iterations: 10_000_000,
width: 1920,
height: 1080,
render: RenderKind::Gas,
transparent: true,
angle: 0.0,
silent: true,
attractor: coefficients,
colors: Colors::default(),
view,
color_transform: transform_colors,
}
}
}
impl Config<attractors::PolynomialSprott2Degree, color_transforms::Function> {
pub fn poisson_saturne() -> Self {
let coeffs = attractors::PolynomialSprott2Degree {
x: [
0.021, 1.182, -1.183, 0.128, -1.12, -0.641, -1.152, -0.834, -0.97, 0.722,
],
y: [
0.243_038, -0.825, -1.2, -0.835_443, -0.835_443, -0.364_557, 0.458, 0.622_785,
-0.394_937, -1.032_911,
],
z: [
-0.455_696, 0.673, 0.915, -0.258_228, -0.495, -0.264, -0.432, -0.416, -0.877,
-0.3,
],
};
let view = View {
/*
`TODO`: Add option to make first-pass to get these values, to then compute `center_camera`
Attractor size of the above
xmin = -0.327770, xmax = 0.335278 width 0.66
ymin = -0.012949, ymax = 0.492107 width 0.50
zmin = -0.628829, zmax = 0.103010 width 0.73
*/
center_camera: Vec3::new(
-0.005,
0.262,
/* mid point between z[min,max]. constant 0.12 works well, don't know why we need that */
-0.366 + 0.12,
),
rotation: EulerAxisRotation {
axis: Vec3 {
x: 0.304_289_493_528_802,
y: 0.760_492_682_863_655,
z: 0.573_636_455_813_981,
},
rotation: 1.782_681_918_874_46,
},
scale: 1.,
};
Self::new(coeffs, view, color_transforms::poisson_saturne)
}
}
impl Config<attractors::PolynomialSprott2Degree, color_transforms::AdjustedVelocity> {
pub fn solar_sail() -> Self {
let coeffs = attractors::PolynomialSprott2Degree {
x: [
0.744_304, -0.546_835, 0.121_519, -0.653_165, 0.399, 0.379, 0.44, 1.014,
-0.805_063, 0.377,
],
y: [
-0.683, 0.531_646, -0.04557, -1.2, -0.546_835, 0.091_139, 0.744_304,
-0.273_418, -0.349_367, -0.531_646,
],
z: [
0.712, 0.744_304, -0.577_215, 0.966, 0.04557, 1.063_291, 0.01519, -0.425_316,
0.212_658, -0.01519,
],
};
let view = View {
center_camera: Vec3::new(0.28, -0.12, 0.22),
rotation: EulerAxisRotation {
axis: Vec3::new(0.02466, 0.4618, -0.54789),
rotation: 2.2195,
},
scale: 1.7,
};
Self::new(
coeffs,
view,
color_transforms::AdjustedVelocity {
factor: -0.2,
offset: 0.8,
},
)
}
}
#[derive(Debug, Clone, Copy)]
pub struct BrighnessConstants {
/// adds this to the colour before multiplying [`Self::factor`].
/// Can be used to add contrast.
/// This is usually what you want.
pub offset: f64,
pub factor: f64,
}
impl Default for BrighnessConstants {
fn default() -> Self {
Self {
offset: -0.15,
factor: 5. / 3.,
}
}
}
#[derive(Debug, Clone)]
#[must_use]
pub struct Palette {
list: Vec<Rgb<f64>>,
count_f64: f64,
}
impl Palette {
/// # Panics
///
/// Panics if `list.is_empty()`.
pub fn new(mut list: Vec<Rgb<f64>>) -> Self {
list.reserve_exact(1);
list.push(*list.last().unwrap());
#[allow(clippy::cast_precision_loss)]
Self {
count_f64: (list.len() - 1) as _,
list,
}
}
pub fn from_rgb<const LEN: usize>(r: [f64; LEN], g: [f64; LEN], b: [f64; LEN]) -> Self {
let mut colors = Vec::with_capacity(LEN + 1);
for i in 0..LEN {
colors.push(Rgb([r[i], g[i], b[i]]));
}
Self::new(colors)
}
/// Number of colours in this palette.
#[inline(always)]
#[must_use]
pub fn count(&self) -> usize {
self.list.len() - 1
}
/// `value` is position in color wheel, in the range [0..1)
/// If `value` is out of that range, it's clamped.
#[inline(always)]
#[must_use]
pub fn interpolate(&self, value: f64) -> Rgb<f64> {
let value = if value < 0. {
0.
} else if value >= 1. {
0.999_999
} else {
value
};
let value = value * self.count_f64;
#[allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
let n = (value.floor()) as usize;
let sub_n_offset = value % 1.;
let sub_n_offset_1 = 1.0 - sub_n_offset;
// SAFETY: we asserted above that `value` is in an appropriate range for this.
let [r1, g1, b1] = unsafe { self.list.get_unchecked(n).0 };
let [r2, g2, b2] = unsafe { self.list.get_unchecked(n + 1).0 };
Rgb([
// lerp between colours
//
// the lerp is inlined to avoid multiple subtractions, about 3% performance increase
// (r[n + 1].lerp(r[n], sub_n_offset)).sqrt(),
// (g[n + 1].lerp(g[n], sub_n_offset)).sqrt(),
// (b[n + 1].lerp(b[n], sub_n_offset)).sqrt(),
//
(r2 * sub_n_offset + r1 * sub_n_offset_1).sqrt(),
(g2 * sub_n_offset + g1 * sub_n_offset_1).sqrt(),
(b2 * sub_n_offset + b1 * sub_n_offset_1).sqrt(),
])
}
}
#[derive(Debug, Clone)]
pub struct Colors {
pub palette: Palette,
pub brighness: BrighnessConstants,
}
impl Default for Colors {
fn default() -> Self {
Self {
palette: Palette::from_rgb(
[1., 0.5, 1., 0.5, 0.5, 1.],
[1., 1., 0.5, 1., 0.5, 0.5],
[0.5, 0.5, 0.5, 1., 1., 1.],
),
brighness: BrighnessConstants::default(),
}
}
}
/// Transformations for getting the position on the palette used in colouring.
/// Returned values should range between [0..1).
/// All functions used as [colour transforms](Config::color_transform) must take three
/// arguments - the Δp, the position in screen space, and the [`View`].
pub mod color_transforms {
use super::{ColorTransform, Vec3, View};
use std::f64::consts::PI;
/// The raw function transform.
pub type Function = fn(Vec3, Vec3, &View) -> f64;
/// Calculated as `(delta.magnitude() + offset) * factor`.
#[derive(Clone, Debug)]
pub struct AdjustedVelocity {
pub offset: f64,
pub factor: f64,
}
impl ColorTransform for AdjustedVelocity {
#[inline(always)]
fn transform(&self, delta: Vec3, _screen_space: Vec3, _view: &View) -> f64 {
(delta.magnitude() + self.offset) * self.factor
}
}
#[must_use]
#[inline(always)]
#[allow(clippy::doc_markdown)]
pub fn poisson_saturne(delta: Vec3, screen_space: Vec3, coeffs: &View) -> f64 {
#[inline(always)]
fn part(p: Vec3, coeffs: &View) -> f64 {
#[allow(unused)] // clarity
const RADIAN_45_5: f64 = 91. * PI / 360.;
/// [`RADIAN_45_5`].cos()
///
/// This was calculated using Rust on x64 Linux.
#[allow(clippy::excessive_precision)]
const COS: f64 =
0.700_909_264_299_850_898_183_308_345_323_894_172_906_875_610_351_562_5;
/// [`RADIAN_45_5`].sin()
///
/// This was calculated using Rust on x64 Linux.
#[allow(clippy::excessive_precision)]
const SIN: f64 =
0.713_250_449_154_181_564_992_427_411_198_150_366_544_723_510_742_187_5;
let x2 =
(p.x + coeffs.center_camera.x) * COS + (p.z + coeffs.center_camera.y) * SIN;
// This computes which "part" of the poisson saturne attractor the current point is
// in (in screen space) by comparing the points to limiting "planes"
if x2 < -0.0839
|| 10.55 * x2 + p.y < 0.46 - 1.0941
|| 1.0426 * x2 + p.y < 0.179 - 0.1576
|| 0.5139 * x2 - p.y > -0.04 - 0.04092
{
0.
} else {
1.
}
}
// Using the part here means we shift half the palette (it's divided by two).
// To not make the returned value return more than 1, we adjust the |Δp| (magnitude of
// point delta). First by dividing by 2, then by subtracting the whole (with the part
// data) by 0.1, then dividing by 0.9.
let color = (part(screen_space, coeffs) + delta.magnitude()) / 2.;
(color - 0.1) / 0.9
}
}
}
/// The included attractors.
///
/// > You can always implement [`Attractor`] yourself!
///
/// These are majorly inspired from [chaoscope](http://chaoscope.org/manual.htm)'s manual.
pub mod attractors {
use super::{Attractor, FloatExt, Vec3};
/// Coefficients for a polynomial Sprott type attractor, of the second degree.
/// See this page from [chaoscope](http://www.chaoscope.org/doc/attractors.htm) for more
/// context.
#[derive(Debug, Clone)]
#[must_use]
pub struct PolynomialSprott2Degree {
// coefficient lists
pub x: [f64; 10],
pub y: [f64; 10],
pub z: [f64; 10],
}
/// This is part of the polynomial Sprott algorithm. We get the new coordinates by multiplying previous
/// (using polynomials) with a set of coefficients.
impl Attractor for PolynomialSprott2Degree {
#[inline(always)]
fn next_point(&self, p: crate::Vec3) -> crate::Vec3 {
#[inline(always)]
// polynomials is a reference to an array with 10 f64s.
fn sum_coefficients(polynomials: &[f64; 10], coefficients: &[f64; 10]) -> f64 {
let mut sum = 0.;
for i in 0..10 {
// unsafe to circumvent bounds checks, increasing speed
// SAFETY: we know 0..10 is in bounds of the array of length 10 (i.e. [f64; 10])
unsafe {
let v1 = polynomials.get_unchecked(i);
let v2 = coefficients.get_unchecked(i);
sum += v1 * v2;
}
}
sum
}
// monomial (polynomials with only one term)
let monoms = [
1.,
p.x,
p.x.square(),
p.x * p.y,
p.x * p.z,
p.y,
p.y.square(),
p.y * p.z,
p.z,
p.z.square(),
];
Vec3 {
x: sum_coefficients(&monoms, &self.x),
y: sum_coefficients(&monoms, &self.y),
z: sum_coefficients(&monoms, &self.z),
}
}
}
}
/// Convenience alias for an 16-bit RGBA image.
pub type FinalImage = ImageBuffer<Rgba<u16>, Vec<u16>>;
/// Stores data used by the algorithm.
///
/// This enables us to reuse memory.
#[must_use]
pub struct Runtime {
// counts the number of visits to each pixel
count: ImageBuffer<Luma<u32>, Vec<u32>>,
// counts the result of [`config::transforms`]
steps: ImageBuffer<Luma<f64>, Vec<f64>>,
// stores the depth of each pixel (in screen space)
// the range pixel values aren't defined, iterate the whole list to get the minimum and
// maximum.
zbuf: ImageBuffer<Luma<f32>, Vec<f32>>,
// the max number of steps
// used to scale all other pixels in [`Self::steps`], without having to iterate the whole
// texture first.
max: u32,
rng: rand::rngs::SmallRng,
}
impl Runtime {
/// You have to [`Self::set_width_height`] before using this.
fn empty() -> Self {
Self {
count: ImageBuffer::new(0, 0),
steps: ImageBuffer::new(0, 0),
zbuf: ImageBuffer::new(0, 0),
max: 0,
rng: rand::rngs::SmallRng::from_os_rng(),
}
}
/// Creates a new runtime from the dimensions of [`Config`].
pub fn new(config: &Config<impl Attractor, impl ColorTransform>) -> Self {
let mut me = Self::empty();
me.set_width_height(config.width, config.height);
me.reset();
me
}
/// Makes new textures if the width and height don't match the inner textures.
fn set_width_height(&mut self, width: u32, height: u32) {
if self.count.width() != width || self.count.height() != height {
self.count = ImageBuffer::new(width, height);
self.steps = ImageBuffer::new(width, height);
self.zbuf = ImageBuffer::new(width, height);
self.max = 0;
self.reset();
}
}
/// Returns an empty image of any pixel type.
fn image_identity<T: Pixel>() -> ImageBuffer<T, Vec<T::Subpixel>> {
ImageBuffer::from_raw(0, 0, Vec::new()).unwrap()
}
/// Reset this runtime.
#[allow(clippy::missing_panics_doc)] // doesn't happen
pub fn reset(&mut self) {
let width = self.count.width();
let height = self.count.height();
let count = mem::replace(&mut self.count, Self::image_identity());
let mut count = count.into_raw();
count.fill(0);
let steps = mem::replace(&mut self.steps, Self::image_identity());
let mut steps = steps.into_raw();
steps.fill(0.);
let zbuf = mem::replace(&mut self.zbuf, Self::image_identity());
let mut zbuf = zbuf.into_raw();
zbuf.fill(-1.);
self.max = 0;
self.count = ImageBuffer::from_raw(width, height, count).unwrap();
self.steps = ImageBuffer::from_raw(width, height, steps).unwrap();
self.zbuf = ImageBuffer::from_raw(width, height, zbuf).unwrap();
}
/// Merges the data of the two images. `other` will not be modified.
/// This makes `self` appear as if it had been rendered with the
/// sum of the iterations of `self` and `other`.
///
/// # Panics
///
/// Panics if the dimensions of `self` isn't the same as the dimensions of `other`.
pub fn merge(&mut self, other: &Self) {
assert_eq!(self.steps.width(), other.steps.width());
assert_eq!(self.steps.height(), other.steps.height());
for x in 0..(self.steps.width()) {
for y in 0..(self.steps.height()) {
unsafe {
let mut pixel = self.count.unsafe_get_pixel(x, y);
let other_pixel = other.count.unsafe_get_pixel(x, y);
// `.0[0]` since the pixel is wrapped in a `Luma`, which contains a unnamed slice (`.0`),
// which we get the first and only element of (`[0]`)
pixel.0[0] += other_pixel.0[0];
self.count.unsafe_put_pixel(x, y, pixel);
if pixel.0[0] > self.max {
self.max = pixel.0[0];
}
};
let zbuf_pix1 = unsafe { self.zbuf.unsafe_get_pixel(x, y) };
let zbuf_pix2 = unsafe { other.zbuf.unsafe_get_pixel(x, y) };
if zbuf_pix2.0[0] > zbuf_pix1.0[0] {
unsafe {
let other_step = other.steps.unsafe_get_pixel(x, y);
self.steps.unsafe_put_pixel(x, y, other_step);
self.zbuf.unsafe_put_pixel(x, y, zbuf_pix2);
}
}
}
}
}
}
/// Render according to `config`, with angle `rotation` around the attractor.
///
/// If the [`Runtime`] isn't [cleared](Runtime::reset), this just continues the "building" of the
/// image. This can therefore be called in succession and the result is an ever-improving image.
///
/// `rotation` is around [`View::center_camera`], in radians.
#[allow(clippy::many_single_char_names)]
pub fn render(config: &Config<impl Attractor, impl ColorTransform>, runtime: &mut Runtime) {
let mut initial_point = runtime.rng.random::<Vec3>() * 0.1;
// skip first 1000 to get good values in the attractor
for _ in 0..1000 {
initial_point = config.attractor.next_point(initial_point);
}
// computations used later - we do as much work up front as possible
let rotation_matrix = config.view.rotation.to_rotation_matrix();
let sin_v = config.angle.sin();
let cos_v = config.angle.cos();
let center_camera = config.view.center_camera;
#[allow(clippy::cast_lossless)]
let width = config.width as f64;
#[allow(clippy::cast_lossless)]
let height = config.height as f64;
let width_scaled = width * config.view.scale;
let scale_adjusted_mid = 0.5 / config.view.scale;
let mut previous_point = initial_point;
let mut current_point = initial_point;
for _ in 0..(config.iterations) {
current_point = config.attractor.next_point(current_point);
// rotation_matrix * current_point
let screen_space = rotation_matrix.mul_right(current_point);
// rotate around center_camera
let x2 =
(screen_space.x + center_camera.x) * cos_v + (screen_space.z + center_camera.y) * sin_v;
let z2 =
(screen_space.x + center_camera.x) * sin_v - (screen_space.z + center_camera.y) * cos_v;
// (0.5 - x2 * scale) * width, but optimized to use constants, so we don't have the
// multiplication
let i = (scale_adjusted_mid - x2) * width_scaled;
// instead of 0.5width as above, we have 0.5height as the center point. The scaling of the
// position relative to that is still width, as we want to keep the shape
let j = height / 2. - (screen_space.y + center_camera.z) * width_scaled;
// do bounds checks
if i >= width || j >= height || i < 0. || j < 0. {
// this is incredibly important:
// if we don't set the previous point, if we don't follow the path, even if the point
// is outside the viewport, the delta is used in colouring.
previous_point = current_point;
continue;
}
// convert floats to image coordinates
// this is safe, as we checked the bounds above.
#[allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
let i = i as u32;
#[allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
let j = j as u32;
// unsafe because we use unsafe functions to get pixel values without checking bounds of
// inner slice. We know the values are within bounds, as by the if ... { continue; } block
// above.
unsafe {
let mut pixel = runtime.count.unsafe_get_pixel(i, j);
// `.0[0]` since the pixel is wrapped in a `Luma`, which contains a unnamed slice (`.0`),
// which we get the first and only element of (`[0]`)
pixel.0[0] += 1;
runtime.count.unsafe_put_pixel(i, j, pixel);
if pixel.0[0] > runtime.max {
runtime.max = pixel.0[0];
}
};
let zbuf_pix = unsafe { runtime.zbuf.unsafe_get_pixel(i, j) };
#[allow(clippy::cast_possible_truncation)]
// if new depth is greater than previous, change that pixel
if z2 as f32 > zbuf_pix.0[0] {
let delta = current_point - previous_point;
// get the colour transformation output, later used in colouring as the index to the
// palette
let value = config
.color_transform
.transform(delta, screen_space, &config.view);
unsafe {
runtime.steps.unsafe_put_pixel(i, j, Luma([value]));
runtime.zbuf.unsafe_put_pixel(i, j, Luma([z2 as f32]));
}
}
previous_point = current_point;
}
}
#[must_use]
#[allow(clippy::missing_panics_doc)]
pub fn colorize(
config: &Config<impl Attractor, impl ColorTransform>,
runtime: &Runtime,
) -> FinalImage {
let bk = config.colors.brighness;
let mut image = ImageBuffer::new(config.width, config.height);
let u16_max = f64::from(u16::MAX);
// ignore lints
#[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
match config.render {
RenderKind::Gas => {
for ((x, y, steps), count) in
runtime.steps.enumerate_pixels().zip(runtime.count.pixels())
{
let color = config.colors.palette.interpolate(steps.0[0]);
let [r, g, b] = color.0;
// add 1 to both to not get any logs of values under 1.
let factor = f64::from(count.0[0] + 1).log(f64::from(runtime.max + 1));
let pixel = Rgba([
((r * factor + bk.offset) * bk.factor * u16_max) as _,
((g * factor + bk.offset) * bk.factor * u16_max) as _,
((b * factor + bk.offset) * bk.factor * u16_max) as _,
if config.transparent {
(factor * u16_max) as u16
} else {
u16::MAX
},
]);
// safety: `image` has the same size as all the others
unsafe { image.unsafe_put_pixel(x, y, pixel) };
}
}
RenderKind::Depth => {
#[allow(clippy::float_cmp)] // the -1.0 value is set by us
let (max, min) = runtime
.zbuf
.pixels()
.map(|pixel| pixel.0[0])
.filter(|p| *p != -1.0)
.fold((0.0f32, f32::MAX), |(a1, a2), p| (a1.max(p), a2.min(p)));
let diff = max - min;
for (x, y, z) in runtime.zbuf.enumerate_pixels() {
let z = z.0[0];
#[allow(clippy::float_cmp)]
// if z hasn't changed from default, we return 0.
let z = if z == -1.0 {
0.0
} else {
// reverse lerp
(z - min) / diff
};
let z = (z * f32::from(u16::MAX)) as u16;
let pixel = Rgba([z, z, z, u16::MAX]);
// safety: `image` has the same size as all the others
unsafe { image.unsafe_put_pixel(x, y, pixel) };
}
}
}
image
}
/// Handle to threads and channels to render a config on multiple threads.
#[must_use]
pub struct ParallelRenderer<A: Attractor, T: ColorTransform> {
threads: Vec<JoinHandle<()>>,
render_receiver: mpsc::Receiver<Arc<Mutex<Runtime>>>,
// `TODO`: make the config we send dynamic and downcast, so we don't have to have this
// generic.
#[allow(clippy::type_complexity)]
job_sender: watch::WatchSender<Option<(Config<A, T>, Arc<AtomicUsize>)>>,
}
impl<A: Attractor + Send + Sync + 'static, T: ColorTransform> ParallelRenderer<A, T> {
/// Initiate an appropriate amount of threads and set them up to accept jobs.
#[allow(clippy::missing_panics_doc)]
pub fn new() -> Self {
let num_threads = std::thread::available_parallelism()
.unwrap_or(std::num::NonZeroUsize::new(8).unwrap())
.get();
let mut threads = Vec::with_capacity(num_threads);
let (job_sender, mut job_receiver) = watch::channel(None);
// get the first, `None` value.
job_receiver.wait();
let (render_sender, render_receiver) = mpsc::channel();
for _ in 0..num_threads {
let receiver = job_receiver.clone();
let sender = render_sender.clone();
let handle = std::thread::spawn(move || {
let mut receiver = receiver;
let sender = sender;
let runtime = Arc::new(Mutex::new(Runtime::empty()));
loop {
let (config, job_counter): (Config<_, _>, Arc<AtomicUsize>) =
if let Some(m) = receiver.wait() {
m
} else {
return;
};
{
let mut rt = runtime.lock().unwrap();
rt.set_width_height(config.width, config.height);
rt.reset();
if !config.silent {
println!("Rendering started on thread.");
}
loop {
// apply the function to check if we should continue.
// This also updates the atomic value.
//
// A `updated` valuable is needed to only decrement once.
let mut updated = false;
let more_to_do = job_counter
.fetch_update(
atomic::Ordering::SeqCst,
atomic::Ordering::SeqCst,
|v| {
if v > 0 {
if updated {
Some(v)
} else {
if !config.silent {
println!("Iteration complete, {v} left to go.");
}
updated = false;
Some(v - 1)
}
} else {
None
}
},
)
.is_ok();
if !more_to_do {
break;
}
render(&config, &mut rt);
}
}
sender.send(Arc::clone(&runtime)).unwrap();
if !config.silent {
println!("Rendered finished.");
}
}
});
threads.push(handle);
}
println!("Created parallel renderer.");
Self {
threads,
render_receiver,
job_sender,
}
}
/// Send the `job` to all threads.
fn send(&mut self, job: Config<A, T>, job_counter: Arc<AtomicUsize>) {
self.job_sender.send(Some((job, job_counter)));
}
/// Blocks on receiving access to the thread's runtimes.
/// Access them though the [`Mutex`].
fn recv(&mut self) -> impl Iterator<Item = Arc<Mutex<Runtime>>> + '_ {
self.render_receiver.iter().take(self.num_threads())
}
/// Number of initiated threads, usually used to construct the `job_counter` at [`Self::send`].
fn num_threads(&self) -> usize {
self.threads.len()
}
/// Wait for all threads to finish.
#[allow(clippy::missing_panics_doc)]
pub fn shutdown(self) {
self.job_sender.send(None);
self.threads
.into_iter()
.for_each(|thread| thread.join().expect("render thread panicked"));
}
}
impl<A: Attractor + Send + Sync + 'static, T: ColorTransform> Default for ParallelRenderer<A, T> {
fn default() -> Self {
Self::new()
}
}
/// I recommend `16` for `jobs_per_thread`. If you get uneven images with low iteration counts, try
/// `8`.
///
/// At relatively low rations between iterations and pixels (<50), this isn't much faster.
///
/// # How it works
///
/// Because strange attractors are inherently chaotic, we can render multiply images and then add
/// them together.
/// Internally, this uses three textures, `count` for the number of visits to the pixel, `steps`
/// for the velocity at the closest visitation, and the `zbuf` which can give information about
/// which pixel is the closest. The `zbuf` also gives us the depth texture.
/// When combining the rendered image, we have to combine all of these.
///
/// When rendering through [`render`] without resetting the [`Runtime`], this is what naturally
/// happens. When we use multiple threads however, we have to explicitly combine the runtimes
/// consistently to what the [`render`] method implicitly does.
#[allow(clippy::missing_panics_doc)] // it won't panic
#[must_use]
pub fn render_parallel<A: Attractor + Send + Sync + 'static, T: ColorTransform>(
renderer: &mut ParallelRenderer<A, T>,
mut config: Config<A, T>,
jobs_per_thread: usize,
) -> FinalImage {
let iterations = config.iterations;
// split up in num_threads and jobs_per_thread
config.iterations = iterations / renderer.num_threads() / jobs_per_thread;
// We keep a job counter to balance threads. If one is way slower, it'll "take" less jobs,
// which results in better runtime.
let job_counter = Arc::new(AtomicUsize::new(jobs_per_thread * renderer.num_threads()));
// send the job
renderer.send(config.clone(), job_counter);
// wait for the job
let mut iter = renderer.recv();
// UNWRAP: `available_parallelism` is guaranteed to always return >0
let current = iter.next().unwrap();
// merge all images
for runtime in iter {
let mut a = current.lock().unwrap();
let b = runtime.lock().unwrap();
a.merge(&b);
}
{
let current = current.lock().unwrap();
colorize(&config, ¤t)
}
}