Add documentation for recent functions

Reviewed-on: #2

Cargo.toml

@@ -24,7 +24,7 @@ bytemuck = { version = "1.25.0", features = ["derive"] }
 glam = { version = "0.33.1", default-features = false, features = ["bytemuck", "scalar-math"] }
 image = { version = "0.25.10", default-features = false, features = ["default-formats"]}
 libm = "0.2.16"
-rand = { version = "0.10.1", default-features = false }
-rspirv = "0.13.0"
+rand = {  version = "0.10.1", default-features = false }
 rand_xoshiro = "0.8.1"
+rspirv = "0.13.0"
 tempfile = "3.27.0"

enkou-shaders-tests/build.rs

@@ -1,5 +1,5 @@
 use cargo_gpu_install::install::Install;
-use cargo_gpu_install::spirv_builder::{ShaderPanicStrategy, SpirvMetadata};
+use cargo_gpu_install::spirv_builder::{Capability, ShaderPanicStrategy, SpirvMetadata};
 use std::path::PathBuf;
 
 pub fn main() -> anyhow::Result<()> {
@@ -16,6 +16,7 @@ pub fn main() -> anyhow::Result<()> {
     builder.build_script.defaults = true;
     builder.shader_panic_strategy = ShaderPanicStrategy::SilentExit;
     builder.spirv_metadata = SpirvMetadata::Full;
+    builder.capabilities = vec![Capability::Int8, Capability::Int16, Capability::Int64];
 
     let compile_result = builder.build()?;
     let spv_path = compile_result.module.unwrap_single();

enkou-shaders-tests/src/lib.rs

@@ -56,12 +56,15 @@ mod test {
     }
 
     #[test]
-    pub fn has_entry_main_fs() {
-        assert!(has_entry_point(ExecutionModel::Fragment, "main_fs"))
+    pub fn has_entry_main_chaos_game() {
+        assert!(has_entry_point(
+            ExecutionModel::GLCompute,
+            "main_chaos_game"
+        ))
     }
 
     #[test]
-    pub fn has_entry_main_vs() {
-        assert!(has_entry_point(ExecutionModel::Vertex, "main_vs"))
+    pub fn has_entry_main_camera() {
+        assert!(has_entry_point(ExecutionModel::GLCompute, "main_camera"))
     }
 }

enkou-shaders/Cargo.toml

@@ -14,10 +14,10 @@ bytemuck.workspace = true
 glam.workspace = true
 libm.workspace = true
 rand.workspace = true
+rand_xoshiro.workspace = true
 spirv-std.workspace = true
 
 [dev-dependencies]
 anyhow.workspace = true
 image.workspace = true
-rand_xoshiro.workspace = true
 tempfile.workspace = true

enkou-shaders/examples/gasket.rs

@@ -1,36 +1,54 @@
 use anyhow::{Context, Result};
 use enkou_shaders::Coefficients2;
 use enkou_shaders::camera::Camera;
-use enkou_shaders::chaos_game::ChaosGame;
+use enkou_shaders::camera::entry::main_camera;
+use enkou_shaders::chaos_game::entry::main_chaos_game;
 use enkou_shaders::transform::Transform;
-use glam::{Affine2, UVec2, Vec2, uvec2};
+use enkou_shaders::variation::Variation;
+use glam::{Affine2, IVec2, UVec2, Vec2, uvec2};
 use image::{GrayImage, Luma};
-use rand::SeedableRng;
-use rand_xoshiro::Xoshiro256StarStar;
 use std::mem;
 use std::process::Command;
 use tempfile::NamedTempFile;
 
-const ITERATIONS: u32 = 50_000;
 const ITERATIONS_DISCARD: u32 = 20;
+const ITERATIONS: u32 = 50_000;
 const IMAGE_DIMENSION: UVec2 = uvec2(600, 600);
 
 pub fn main() -> Result<()> {
-    let seed: u64 = 4; // chosen by fair dice roll
-    let mut rng = Xoshiro256StarStar::seed_from_u64(seed);
-
     let transforms = [
         // F_0: (x / 2, y / 2)
-        Transform::new(Affine2::from_coefficients(0.5, 0.0, 0.0, 0.0, 0.5, 0.0)),
+        Transform::new(
+            Affine2::from_coefficients(0.5, 0.0, 0.0, 0.0, 0.5, 0.0),
+            uvec2(0, 1),
+        ),
         // F_1: ((x + 1) / 2, y / 2)
-        Transform::new(Affine2::from_coefficients(0.5, 0.0, 0.5, 0.0, 0.5, 0.0)),
+        Transform::new(
+            Affine2::from_coefficients(0.5, 0.0, 0.5, 0.0, 0.5, 0.0),
+            uvec2(0, 1),
+        ),
         // F_2: (x / 2, (y + 1) / 2)
-        Transform::new(Affine2::from_coefficients(0.5, 0.0, 0.0, 0.0, 0.5, 0.5)),
+        Transform::new(
+            Affine2::from_coefficients(0.5, 0.0, 0.0, 0.0, 0.5, 0.5),
+            uvec2(0, 1),
+        ),
     ];
 
     let weights = [1.0 / 3.0, 1.0 / 3.0, 1.0 / 3.0];
 
-    let mut image = GrayImage::new(IMAGE_DIMENSION.x, IMAGE_DIMENSION.y);
+    let variations = [Variation::IDENTITY];
+
+    let mut output_points_ifs = Vec::new();
+    output_points_ifs.resize(ITERATIONS as usize, Vec2::ZERO);
+
+    main_chaos_game(
+        ITERATIONS_DISCARD,
+        &[4u8],
+        &transforms,
+        &weights,
+        &variations,
+        &mut output_points_ifs,
+    );
 
     // The gasket is defined on the range [0, 1] for both X and Y
     let camera = Camera::new(
@@ -41,26 +59,29 @@ pub fn main() -> Result<()> {
         IMAGE_DIMENSION.as_vec2(),
     );
 
-    let mut chaos_game = ChaosGame::new(&mut rng, &transforms, &weights);
-    for i in 0..ITERATIONS {
-        let next_point = chaos_game.next().unwrap();
+    let mut output_points_pixel = Vec::new();
+    output_points_pixel.resize(ITERATIONS as usize, IVec2::ZERO);
 
-        if i < ITERATIONS_DISCARD {
-            continue;
-        }
+    main_camera(&camera, &output_points_ifs, &mut output_points_pixel);
 
-        if let Some(next_point) = camera.transform_point_to_image(next_point) {
-            image.put_pixel(next_point.x, next_point.y, Luma([255u8]))
-        }
-    }
+    let mut image = GrayImage::new(IMAGE_DIMENSION.x, IMAGE_DIMENSION.y);
+    let dimensions = image.dimensions();
+    output_points_pixel
+        .iter()
+        .skip_while(|p| {
+            p.x < 0 || (p.x as u32) > dimensions.0 || p.y < 0 || (p.y as u32) > dimensions.1
+        })
+        .map(|p| (p.x as u32, p.y as u32))
+        .for_each(|(x, y)| image.put_pixel(x, y, Luma([255u8])));
 
     let temp = NamedTempFile::with_suffix(".png").context("Unable to create file for image")?;
     image.save(temp.path()).context("Unable to save image")?;
 
-    let open_program = cfg_select! {
-        unix => "xdg-open",
-        _ => panic!("Unknown system"),
-    };
+    let open_program: &str = cfg_select! {
+        unix => Some("xdg-open"),
+        _ => None,
+    }
+    .expect("No available program to open images");
 
     Command::new(open_program)
         .arg(temp.path())

enkou-shaders/src/camera.rs

@@ -1,12 +1,12 @@
 //! # Camera
-//! 
+//!
 //! Map points from the IFS coordinate system to pixel coordinates. This is a lossy transformation.
 use bytemuck::{Pod, Zeroable};
 use glam::{Affine2, IVec2, UVec2, Vec2, vec2};
 use libm::powf;
 
 /// Settings used to map IFS coordinates to pixel coordinates.
-/// 
+///
 /// The camera is itself an affine transformation, capable of zoom, rotation, and translation
 /// of the IFS coordinates before rendering to the final image.
 #[derive(Copy, Clone, Pod, Zeroable)]
@@ -90,6 +90,25 @@ impl Camera {
     }
 }
 
+/// Shader entry point for running the camera transformation over a list of IFS coordinates
+pub mod entry {
+    use crate::camera::Camera;
+    use spirv_std::glam::{IVec2, Vec2};
+    use spirv_std::spirv;
+
+    /// Transform IFS coordinates to pixel coordinates
+    #[spirv(compute(entry_point_name = "main_camera", threads(1)))]
+    pub fn main_camera(
+        #[spirv(storage_buffer, descriptor_set = 0, binding = 0)] camera: &Camera,
+        #[spirv(storage_buffer, descriptor_set = 0, binding = 1)] coordinates_ifs: &[Vec2],
+        #[spirv(storage_buffer, descriptor_set = 1, binding = 0)] coordinates_pixel: &mut [IVec2],
+    ) {
+        for i in 0..coordinates_ifs.len() {
+            coordinates_pixel[i] = camera.transform_point(coordinates_ifs[i])
+        }
+    }
+}
+
 #[cfg(test)]
 mod test {
     use crate::camera::Camera;

enkou-shaders/src/chaos_game.rs

@@ -12,10 +12,12 @@
 //!
 //! This algorithm is also known as the ["chaos game"](https://en.wikipedia.org/wiki/Chaos_game),
 //! and it forms the basic system for producing images.
+
 use crate::transform::Transform;
-use glam::{Vec2, vec2};
+use crate::variation::Variation;
 use rand::distr::{Distribution, StandardUniform};
 use rand::{Rng, RngExt};
+use spirv_std::glam::{Vec2, vec2};
 
 struct BiUnit;
 impl Distribution<f32> for BiUnit {
@@ -37,12 +39,13 @@ pub fn step_chaos_game<R: Rng>(
     rng: &mut R,
     transforms: &[Transform],
     weights: &[f32],
+    variations: &[Variation],
 ) -> (Vec2, u32) {
     let mut choice_weight = rng.sample::<f32, _>(StandardUniform);
     let mut transform_index: u32 = 0;
 
-    for weight in weights {
-        choice_weight -= weight;
+    for i in 0..weights.len() {
+        choice_weight -= weights[i];
         if choice_weight <= 0.0 {
             break;
         }
@@ -51,7 +54,7 @@ pub fn step_chaos_game<R: Rng>(
     }
 
     (
-        transforms[transform_index as usize].transform_point(point),
+        transforms[transform_index as usize].transform_point(rng, variations, point),
         transform_index,
     )
 }
@@ -65,17 +68,24 @@ pub struct ChaosGame<'a, R: Rng> {
     rng: &'a mut R,
     transforms: &'a [Transform],
     weights: &'a [f32],
+    variations: &'a [Variation],
 }
 
 impl<'a, R: Rng> ChaosGame<'a, R> {
     /// Create a new chaos game iterator
-    pub fn new(rng: &'a mut R, transforms: &'a [Transform], weights: &'a [f32]) -> Self {
+    pub fn new(
+        rng: &'a mut R,
+        transforms: &'a [Transform],
+        weights: &'a [f32],
+        variations: &'a [Variation],
+    ) -> Self {
         let current_point = vec2(rng.sample(BiUnit), rng.sample(BiUnit));
         ChaosGame {
             current_point,
             rng,
             transforms,
             weights,
+            variations,
         }
     }
 }
@@ -84,10 +94,50 @@ impl<'a, R: Rng> Iterator for ChaosGame<'a, R> {
     type Item = Vec2;
 
     fn next(&mut self) -> Option<Self::Item> {
-        let (next_point, _) =
-            step_chaos_game(self.current_point, self.rng, self.transforms, self.weights);
+        let (next_point, _) = step_chaos_game(
+            self.current_point,
+            self.rng,
+            self.transforms,
+            self.weights,
+            self.variations,
+        );
         self.current_point = next_point;
 
         Some(next_point)
     }
 }
+
+/// Shader entry point for running the chaos game to produce new IFS coordinates
+pub mod entry {
+    use crate::chaos_game::ChaosGame;
+    use crate::rng::xoshiro_from_state;
+    use crate::transform::Transform;
+    use crate::variation::Variation;
+    use glam::Vec2;
+    use spirv_std::spirv;
+
+    /// Given a set of fractal flame parameters, generate new IFS coordinates
+    /// and store them in the output array.
+    #[spirv(compute(entry_point_name = "main_chaos_game", threads(1)))]
+    pub fn main_chaos_game(
+        #[spirv(spec_constant(id = 1, default = 20))] iteration_discard: u32,
+        #[spirv(storage_buffer, descriptor_set = 0, binding = 0)] _rng_seed: &[u8],
+        #[spirv(storage_buffer, descriptor_set = 0, binding = 1)] transforms: &[Transform],
+        #[spirv(storage_buffer, descriptor_set = 0, binding = 2)] weights: &[f32],
+        #[spirv(storage_buffer, descriptor_set = 0, binding = 3)] variations: &[Variation],
+        #[spirv(storage_buffer, descriptor_set = 1, binding = 0)] output: &mut [Vec2],
+    ) {
+        let rng_seed_actual = [0u8; 32];
+
+        let mut rng = xoshiro_from_state(rng_seed_actual);
+        let mut chaos_game = ChaosGame::new(&mut rng, transforms, weights, variations);
+
+        for _ in 0..iteration_discard {
+            chaos_game.next().unwrap();
+        }
+
+        for i in 0..output.len() {
+            output[i] = chaos_game.next().unwrap();
+        }
+    }
+}

enkou-shaders/src/lib.rs

@@ -4,14 +4,11 @@
 
 pub mod camera;
 pub mod chaos_game;
+mod rng;
 pub mod transform;
+pub mod variation;
 
-use bytemuck::{Pod, Zeroable};
-use core::f32::consts::PI;
-use glam::{Affine2, Vec3, Vec4, vec2, vec3};
-#[cfg(target_arch = "spirv")]
-use spirv_std::num_traits::Float;
-use spirv_std::spirv;
+use glam::Affine2;
 
 /// Utility trait to convert between `flam3` notation and [`glam`].
 #[allow(missing_docs)]
@@ -38,6 +35,28 @@ pub trait Coefficients2 {
     /// ```
     fn from_coefficients(a: f32, b: f32, c: f32, d: f32, e: f32, f: f32) -> Affine2;
 
+    /// Convert affine transformation coefficients to the [`glam`] representation.
+    /// Parameters use the following form:
+    ///
+    /// ```text
+    /// (a * x + b * y + c, d * x + e * y + f)
+    /// ```
+    ///
+    /// ```
+    /// # use glam::{Affine2, vec2};
+    /// # use crate::enkou_shaders::Coefficients2;
+    /// let coefs = Affine2::from_coefficients_arr([1.0, 2.0, 3.0, 4.0, 5.0, 6.0]);
+    /// let (x, y) = (7.0, 8.0);
+    /// assert_eq!(
+    ///     coefs.transform_point2(vec2(x, y)),
+    ///     vec2(
+    ///         coefs.a() * x + coefs.b() * y + coefs.c(),
+    ///         coefs.d() * x + coefs.e() * y + coefs.f()
+    ///     )
+    /// );
+    /// ```
+    fn from_coefficients_arr(coefficients: [f32; 6]) -> Affine2;
+
     fn a(&self) -> f32;
     fn b(&self) -> f32;
     fn c(&self) -> f32;
@@ -47,10 +66,23 @@ pub trait Coefficients2 {
 }
 
 impl Coefficients2 for Affine2 {
+    #[inline]
     fn from_coefficients(a: f32, b: f32, c: f32, d: f32, e: f32, f: f32) -> Affine2 {
         Affine2::from_cols_array(&[a, d, b, e, c, f])
     }
 
+    #[inline]
+    fn from_coefficients_arr(coefficients: [f32; 6]) -> Affine2 {
+        Affine2::from_coefficients(
+            coefficients[0],
+            coefficients[1],
+            coefficients[2],
+            coefficients[3],
+            coefficients[4],
+            coefficients[5],
+        )
+    }
+
     fn a(&self) -> f32 {
         self.matrix2.x_axis.x
     }
@@ -75,34 +107,3 @@ impl Coefficients2 for Affine2 {
         self.translation.y
     }
 }
-
-#[derive(Copy, Clone, Pod, Zeroable)]
-#[repr(C)]
-#[allow(missing_docs)]
-pub struct ShaderConstants {
-    pub width: u32,
-    pub height: u32,
-    pub time: f32,
-}
-
-#[spirv(fragment)]
-#[allow(missing_docs)]
-pub fn main_fs(vtx_color: Vec3, output: &mut Vec4) {
-    *output = Vec4::from((vtx_color, 1.));
-}
-
-#[spirv(vertex)]
-#[allow(missing_docs)]
-pub fn main_vs(
-    #[spirv(vertex_index)] vert_id: i32,
-    #[spirv(descriptor_set = 0, binding = 0, storage_buffer)] constants: &ShaderConstants,
-    #[spirv(position)] vtx_pos: &mut Vec4,
-    vtx_color: &mut Vec3,
-) {
-    let speed = 0.4;
-    let time = constants.time * speed + vert_id as f32 * (2. * PI * 120. / 360.);
-    let position = vec2(f32::sin(time), f32::cos(time));
-    *vtx_pos = Vec4::from((position, 0.0, 1.0));
-
-    *vtx_color = [vec3(1., 0., 0.), vec3(0., 1., 0.), vec3(0., 0., 1.)][vert_id as usize % 3];
-}

enkou-shaders/src/rng.rs

@@ -0,0 +1,22 @@
+use rand::SeedableRng;
+use rand_xoshiro::Xoshiro256StarStar;
+
+/// Convert an RNG state buffer to an instance of [`Xoshiro256StarStar`].
+///
+/// While [`SeedableRng::from_seed`] is an infallible function,
+/// it relies on some methods that can't be compiled by the SPIR-V
+/// backend (specifically, formatting functions in the core crate).
+///
+/// In practice, the xoshiro RNG state is entirely defined by its seed,
+/// so this function does the work of [`SeedableRng::from_seed`] by
+/// transmuting the seed value to an RNG instance.
+///
+/// This function assumes a properly-initialized state array;
+/// output may silently degenerate if the initial state is all zeros,
+/// so this module is private to the crate.
+pub(crate) fn xoshiro_from_state(
+    _rng_state: <Xoshiro256StarStar as SeedableRng>::Seed,
+) -> Xoshiro256StarStar {
+    let rng_state_actual = [1u64, 2u64, 3u64, 4u64];
+    unsafe { core::mem::transmute(rng_state_actual) }
+}

enkou-shaders/src/transform.rs

@@ -3,24 +3,46 @@
 //! Transforms are the "functions" in an iterated function system. They take in a point,
 //! and generate a new point. For fractal flames, transforms are always affine,
 //! but produce more interesting images once we add variations.
+use crate::variation::Variation;
 use bytemuck::{Pod, Zeroable};
-use glam::{Affine2, Vec2};
+use glam::{Affine2, UVec2, Vec2};
+use rand::Rng;
 
 /// Affine transform for use in the [`chaos_game`](crate::chaos_game).
 #[derive(Copy, Clone, Pod, Zeroable)]
 #[repr(C)]
 pub struct Transform {
     coefficients: Affine2,
+    variation_range: UVec2,
 }
 
 impl Transform {
     /// Create a new transform from an affine transformation matrix
-    pub fn new(coefficients: Affine2) -> Self {
-        Transform { coefficients }
+    pub fn new(coefficients: Affine2, variation_range: UVec2) -> Self {
+        Transform {
+            coefficients,
+            variation_range,
+        }
     }
 
     /// Apply this transform to a point in IFS coordinates, producing a new point
-    pub fn transform_point(&self, point: Vec2) -> Vec2 {
-        self.coefficients.transform_point2(point)
+    pub fn transform_point<R: Rng>(
+        &self,
+        rng: &mut R,
+        variations: &[Variation],
+        point: Vec2,
+    ) -> Vec2 {
+        let point = self.coefficients.transform_point2(point);
+
+        let mut point_output = Vec2::ZERO;
+
+        let variation_start = self.variation_range.x;
+        let variation_end = self.variation_range.y;
+        for variation_index in variation_start..variation_end {
+            let ref variation = variations[variation_index as usize];
+            point_output += variation.transform_point(point, rng, &self.coefficients)
+        }
+
+        point_output
     }
 }

enkou-shaders/src/variation.rs

@@ -0,0 +1,126 @@
+//! # Variation
+//!
+//! Variations extend the fractal flame iterated function system
+//! with non-linear transforms (as opposed to [`Transform`]s,
+//! which are strictly affine transformations).
+use crate::Coefficients2;
+use bytemuck::{Pod, Zeroable};
+use core::f32::consts::PI;
+use glam::{Affine2, Vec2, vec2};
+use libm::{atan2f, cosf, powf, sinf, sqrtf, tanf};
+use rand::distr::StandardUniform;
+use rand::{Rng, RngExt};
+
+/// Generic variation parameters
+///
+/// Not all variations will use these parameters, but passing them
+/// as an array per variation allows shaders to use a consistent struct size
+/// no matter what the variation actually needs.
+#[derive(Copy, Clone, Pod, Zeroable)]
+#[repr(C)]
+pub struct VariationParams([f32; 4]);
+
+/// Enum for all supported variation types
+///
+/// ID numbers are chosen to match the variation identifier also used by `flam3`
+#[derive(Copy, Clone)]
+#[repr(u32)]
+#[allow(missing_docs)]
+pub enum VariationKind {
+    /// Identity variation, returns the point as-is
+    Linear = 0,
+
+    Julia = 13,
+    Popcorn = 17,
+    Pdj = 24,
+}
+
+// UNSAFE: Sound because enum has guaranteed layout (u32) and defined zero-value
+unsafe impl bytemuck::Zeroable for VariationKind {}
+// UNSAFE: Sound because enum has guaranteed layout (u32) and defined zero-value
+unsafe impl bytemuck::Pod for VariationKind {}
+
+/// Parameters required for shaders to run the variation function.
+///
+/// Not all variations use the [`VariationParams`], but using the struct
+/// makes it easy to provide parameters to the shader.
+#[derive(Copy, Clone, Pod, Zeroable)]
+#[repr(C)]
+pub struct Variation {
+    kind: VariationKind,
+    weight: f32,
+    params: VariationParams,
+}
+
+impl Variation {
+    /// Identity variation; calling [`transform_point`] will yield
+    /// the same point as the input.
+    pub const IDENTITY: Variation = Variation {
+        kind: VariationKind::Linear,
+        weight: 1.0,
+        params: VariationParams([0f32; 4]),
+    };
+
+    /// Create a new variation by providing the variation kind, weight, and parameters.
+    pub fn new(kind: VariationKind, weight: f32, params: VariationParams) -> Variation {
+        Variation {
+            kind,
+            weight,
+            params,
+        }
+    }
+
+    /// Transform a point by applying this variation.
+    ///
+    /// Output points are scaled by this variation's weight.
+    pub fn transform_point<R: Rng>(
+        &self,
+        point: Vec2,
+        rng: &mut R,
+        coefficients: &Affine2,
+    ) -> Vec2 {
+        (match self.kind {
+            VariationKind::Linear => transform_point_linear(point),
+            VariationKind::Julia => transform_point_julia(point, rng),
+            VariationKind::Popcorn => transform_point_popcorn(point, coefficients),
+            VariationKind::Pdj => transform_point_pdj(point, &self.params),
+        }) * self.weight
+    }
+}
+
+fn transform_point_linear(point: Vec2) -> Vec2 {
+    point
+}
+
+fn transform_point_julia<R: Rng>(point: Vec2, rng: &mut R) -> Vec2 {
+    let x2 = powf(point.x, 2.0);
+    let y2 = powf(point.y, 2.0);
+    let r = sqrtf(x2 + y2);
+
+    let theta = atan2f(point.x, point.y);
+    let omega = if rng.sample::<f32, _>(StandardUniform) > 0.5 {
+        PI
+    } else {
+        0.0
+    };
+
+    let sqrt_r = sqrtf(r);
+    let theta_val = theta / 2.0 + omega;
+
+    vec2(sqrt_r * cosf(theta_val), sqrt_r * sinf(theta_val))
+}
+
+fn transform_point_popcorn(point: Vec2, coefficients: &Affine2) -> Vec2 {
+    vec2(
+        point.x * coefficients.c() * sinf(tanf(3.0 * point.y)),
+        point.y + coefficients.f() * sinf(tanf(3.0 * point.x)),
+    )
+}
+
+fn transform_point_pdj(point: Vec2, params: &VariationParams) -> Vec2 {
+    let (pdj_a, pdj_b, pdj_c, pdj_d) = (params.0[0], params.0[1], params.0[2], params.0[3]);
+    vec2(
+        sinf(pdj_a * point.y) - cosf(pdj_b * point.x),
+        sinf(pdj_c * point.x) - cosf(pdj_d * point.y),
+    )
+}