Rustfmt

I was hoping to implement the image filter/reduction step as well, but that seems to be meaningfully more complex

enkou-shaders-tests/src/lib.rs

@@ -53,15 +53,10 @@ mod test {
     }
 
     #[test]
-    pub fn has_entry_main_chaos_game() {
+    fn has_entry_main_camera() {
         assert!(has_entry_point(
             ExecutionModel::GLCompute,
-            "main_chaos_game"
+            "main_image_accumulate"
         ))
     }
-
-    #[test]
-    pub fn has_entry_main_camera() {
-        assert!(has_entry_point(ExecutionModel::GLCompute, "main_camera"))
-    }
 }

enkou-shaders/examples/gasket.rs

@@ -1,36 +1,40 @@
 use anyhow::{Context, Result};
 use enkou_shaders::Coefficients2;
 use enkou_shaders::camera::Camera;
-use enkou_shaders::camera::entry::main_camera;
-use enkou_shaders::chaos_game::entry::main_chaos_game;
+use enkou_shaders::chaos_game::ChaosGame;
+use enkou_shaders::image::{BlendMode, ImageSettings};
 use enkou_shaders::transform::Transform;
 use enkou_shaders::variation::Variation;
-use glam::{Affine2, IVec2, UVec2, Vec2, uvec2};
+use glam::{Affine2, UVec2, Vec2, uvec2, vec2};
 use image::{GrayImage, Luma};
+use rand::SeedableRng;
+use rand_xoshiro::Xoshiro256StarStar;
 use std::mem;
 use std::process::Command;
 use tempfile::NamedTempFile;
 
-const ITERATIONS_DISCARD: u32 = 20;
-const ITERATIONS: u32 = 50_000;
+const ITERATIONS_DISCARD: usize = 20;
+const ITERATIONS: usize = 50_000;
 const IMAGE_DIMENSION: UVec2 = uvec2(600, 600);
 
 pub fn main() -> Result<()> {
+    let mut rng = Xoshiro256StarStar::from_seed([4u8; 32]);
+
     let transforms = [
         {
             // F_0: (x / 2, y / 2)
             let coefficients = Affine2::from_coefficients(0.5, 0.0, 0.0, 0.0, 0.5, 0.0);
-            Transform::new(coefficients, Affine2::IDENTITY, uvec2(0, 1))
+            Transform::new(coefficients, Affine2::IDENTITY, uvec2(0, 1), vec2(0.0, 1.0))
         },
         {
             // F_1: ((x + 1) / 2, y / 2)
             let coefficients = Affine2::from_coefficients(0.5, 0.0, 0.5, 0.0, 0.5, 0.0);
-            Transform::new(coefficients, Affine2::IDENTITY, uvec2(0, 1))
+            Transform::new(coefficients, Affine2::IDENTITY, uvec2(0, 1), vec2(0.0, 1.0))
         },
         {
             // F_2: (x / 2, (y + 1) / 2)
             let coefficients = Affine2::from_coefficients(0.5, 0.0, 0.0, 0.0, 0.5, 0.5);
-            Transform::new(coefficients, Affine2::IDENTITY, uvec2(0, 1))
+            Transform::new(coefficients, Affine2::IDENTITY, uvec2(0, 1), vec2(0.0, 1.0))
         },
     ];
 
@@ -38,18 +42,6 @@ pub fn main() -> Result<()> {
 
     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; 32],
-        &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(
         IMAGE_DIMENSION,
@@ -59,20 +51,18 @@ pub fn main() -> Result<()> {
         IMAGE_DIMENSION.as_vec2(),
     );
 
-    let mut output_points_pixel = Vec::new();
-    output_points_pixel.resize(ITERATIONS as usize, IVec2::ZERO);
-
-    main_camera(&camera, &output_points_ifs, &mut output_points_pixel);
+    let image_settings = ImageSettings::new(BlendMode::Linear, IMAGE_DIMENSION);
 
     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 chaos_game = ChaosGame::new(&mut rng, &transforms, &weights, &variations);
+
+    chaos_game
+        .skip(ITERATIONS_DISCARD)
+        .take(ITERATIONS)
+        .map(|(point_ifs, _)| camera.transform_point(point_ifs))
+        .filter_map(|point_pixel| image_settings.transform_point_to_image(point_pixel))
+        .for_each(|point_pixel| image.put_pixel(point_pixel.x, point_pixel.y, Luma([255])));
 
     let temp = NamedTempFile::with_suffix(".png").context("Unable to create file for image")?;
     image.save(temp.path()).context("Unable to save image")?;

enkou-shaders/src/camera.rs

@@ -12,7 +12,6 @@ use libm::powf;
 #[derive(Copy, Clone, Pod, Zeroable)]
 #[repr(C)]
 pub struct Camera {
-    dimensions: UVec2,
     transform: Affine2,
 }
 
@@ -23,7 +22,7 @@ impl Camera {
     /// to express the transform steps individually.
     ///
     /// # Arguments
-    ///
+    /// * `blend_mode` - Color blending mode for the output image
     /// * `dimensions` - Width and height of the output image (in pixels).
     /// * `center` - Location of the origin in IFS coordinates. Positive `x` shifts the image
     ///   left, and positive `y` position shifts the image up.
@@ -47,10 +46,7 @@ impl Camera {
             * zoom_transform
             * ifs_center_transform;
 
-        Camera {
-            dimensions,
-            transform,
-        }
+        Camera { transform }
     }
 
     /// Map a point from IFS coordinates to pixel coordinates.
@@ -73,40 +69,6 @@ impl Camera {
     pub fn transform_point(&self, point: Vec2) -> IVec2 {
         self.transform.transform_point2(point).as_ivec2()
     }
-
-    /// Map a point from IFS coordinates to pixel coordinates (like [`transform_point`](Camera::transform_point)),
-    /// and check that the result is within the provided image dimensions.
-    pub fn transform_point_to_image(&self, point: Vec2) -> Option<UVec2> {
-        let pixel_coordinates = self.transform_point(point);
-        if pixel_coordinates.x < 0
-            || pixel_coordinates.y < 0
-            || (pixel_coordinates.x as u32) >= self.dimensions.x
-            || (pixel_coordinates.y as u32) >= self.dimensions.y
-        {
-            None
-        } else {
-            Some(pixel_coordinates.as_uvec2())
-        }
-    }
-}
-
-/// 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)]
@@ -116,7 +78,7 @@ mod test {
     use libm::powf;
 
     #[test]
-    pub fn manual_camera() {
+    fn manual_camera() {
         let starting_point = vec2(1.0, 1.0);
 
         // Move the origin; points move right and up by one unit, giving us (2.0, 2.0)
@@ -148,13 +110,14 @@ mod test {
 
         // The camera is implemented by composing affine transforms,
         // which ends up with a slightly different result because of rounding.
-        let error = camera.transform_point(starting_point) - point;
-        assert!(error.x.abs() <= 1);
-        assert!(error.y.abs() <= 1);
+        let error = (camera.transform_point(starting_point) - point)
+            .abs()
+            .as_uvec2();
+        assert!(error.x <= 1 && error.y <= 1);
     }
 
     #[test]
-    pub fn point_outside_camera() {
+    fn point_outside_camera() {
         // Scale 250 for an image 1000 x 1000 gives an effective range of [-2, 2]
         let camera = Camera::new(
             uvec2(1000, 1000),
@@ -169,7 +132,7 @@ mod test {
     }
 
     #[test]
-    pub fn point_outside_camera_negative() {
+    fn point_outside_camera_negative() {
         // Scale 250 for an image 1000 x 1000 gives an effective range of [-2, 2]
         let camera = Camera::new(
             uvec2(1000, 1000),
@@ -184,7 +147,7 @@ mod test {
     }
 
     #[test]
-    pub fn aspect_ratio() {
+    fn aspect_ratio() {
         // Scale 100 for an image 1600 x 900 gives an effective X range of [-8, 8],
         // and effective Y range of [-4.5, 4.5]
         let camera = Camera::new(

enkou-shaders/src/chaos_game.rs

@@ -12,7 +12,6 @@
 //!
 //! 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 crate::variation::Variation;
 use rand::distr::{Distribution, StandardUniform};
@@ -36,11 +35,12 @@ impl Distribution<f32> for BiUnit {
 /// * `weights` - Weights are assumed to be normalized; adding all elements together should return the value 1
 pub fn step_chaos_game<R: Rng>(
     point: Vec2,
+    color: f32,
     rng: &mut R,
     transforms: &[Transform],
     weights: &[f32],
     variations: &[Variation],
-) -> (Vec2, u32) {
+) -> (Vec2, f32, u32) {
     let mut choice_weight = rng.sample::<f32, _>(StandardUniform);
     let mut transform_index: u32 = 0;
 
@@ -53,8 +53,11 @@ pub fn step_chaos_game<R: Rng>(
         transform_index += 1;
     }
 
+    let transform = transforms[transform_index as usize];
+
     (
-        transforms[transform_index as usize].transform_point(rng, variations, point),
+        transform.transform_point(rng, variations, point),
+        transform.transform_color(color),
         transform_index,
     )
 }
@@ -65,6 +68,7 @@ pub fn step_chaos_game<R: Rng>(
 /// New points in the chaos game are produced by iterating on the chaos game.
 pub struct ChaosGame<'a, R: Rng> {
     current_point: Vec2,
+    current_color: f32,
     rng: &'a mut R,
     transforms: &'a [Transform],
     weights: &'a [f32],
@@ -80,8 +84,10 @@ impl<'a, R: Rng> ChaosGame<'a, R> {
         variations: &'a [Variation],
     ) -> Self {
         let current_point = vec2(rng.sample(BiUnit), rng.sample(BiUnit));
+        let current_color = rng.sample(StandardUniform);
         ChaosGame {
             current_point,
+            current_color,
             rng,
             transforms,
             weights,
@@ -91,54 +97,20 @@ impl<'a, R: Rng> ChaosGame<'a, R> {
 }
 
 impl<'a, R: Rng> Iterator for ChaosGame<'a, R> {
-    type Item = Vec2;
+    type Item = (Vec2, f32);
 
     fn next(&mut self) -> Option<Self::Item> {
-        let (next_point, _) = step_chaos_game(
+        let (next_point, next_color, _) = step_chaos_game(
             self.current_point,
+            self.current_color,
             self.rng,
             self.transforms,
             self.weights,
             self.variations,
         );
         self.current_point = next_point;
+        self.current_color = next_color;
 
-        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::xoshiro256starstar_from_seed;
-    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 mut rng_seed_actual = [0u8; 32];
-        (0..32).for_each(|i| rng_seed_actual[i] = rng_seed[i]);
-
-        let mut rng = xoshiro256starstar_from_seed(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();
-        }
+        Some((next_point, next_color))
     }
 }

enkou-shaders/src/entry/image_accumulate.rs

@@ -0,0 +1,63 @@
+//! Image Accumulate
+
+use crate::camera::Camera;
+use crate::chaos_game::ChaosGame;
+use crate::image::ImageSettings;
+use crate::rng::xoshiro256starstar_from_seed;
+use crate::transform::Transform;
+use crate::variation::Variation;
+use glam::{UVec2, Vec4};
+use spirv_std::spirv;
+
+/// Run the chaos game and accumulate points into the output image buffer
+///
+/// # Arguments
+/// * `iterations` - Controls the iteration count; the first `x` iterations are discarded,
+///   the next `y` iterations are accumulated into the output image
+/// * `rng_seed`
+/// * `transforms`
+/// * `weights`
+/// * `variations`
+/// * `camera` - Camera transformation to map IFS coordinates to pixel coordinates
+/// * `image_settings` - Settings to use for image accumulation
+/// * `palette` - List of colors to use for the image palette; assumed to be RGB values scaled to `[0-255]`, with an alpha of 255
+/// * `image` - Output image buffer
+#[spirv(compute(entry_point_name = "main_image_accumulate", threads(1)))]
+pub fn main_image_accumulate(
+    #[spirv(storage_buffer, descriptor_set = 0, binding = 0)] iterations: &UVec2,
+    #[spirv(storage_buffer, descriptor_set = 0, binding = 1)] rng_seed: &[u8],
+    #[spirv(storage_buffer, descriptor_set = 0, binding = 2)] transforms: &[Transform],
+    #[spirv(storage_buffer, descriptor_set = 0, binding = 3)] weights: &[f32],
+    #[spirv(storage_buffer, descriptor_set = 0, binding = 4)] variations: &[Variation],
+    #[spirv(storage_buffer, descriptor_set = 0, binding = 5)] camera: &Camera,
+    #[spirv(storage_buffer, descriptor_set = 0, binding = 6)] image_settings: &ImageSettings,
+    #[spirv(storage_buffer, descriptor_set = 0, binding = 7)] palette: &[Vec4],
+    #[spirv(storage_buffer, descriptor_set = 1, binding = 0)] image: &mut [Vec4],
+) {
+    let mut rng_seed_actual = [0u8; 32];
+    for i in 0..rng_seed_actual.len() {
+        rng_seed_actual[i] = rng_seed[i];
+    }
+
+    let mut rng = xoshiro256starstar_from_seed(rng_seed_actual);
+
+    let chaos_game = ChaosGame::new(&mut rng, transforms, weights, variations);
+    let (iterations_fuse, iterations_accumulate) = (iterations.x, iterations.y);
+
+    let ifs_to_image = |(ifs_point, ifs_color)| {
+        let pixel_coordinates = camera.transform_point(ifs_point);
+        let pixel_color = image_settings.transform_color(ifs_color, palette);
+        image_settings
+            .transform_point_to_index(pixel_coordinates)
+            .map(|pixel_index| (pixel_index, pixel_color))
+    };
+
+    for ifs_point in chaos_game
+        .skip(iterations_fuse as usize)
+        .take(iterations_accumulate as usize)
+    {
+        if let Some((pixel_index, pixel_color)) = ifs_to_image(ifs_point) {
+            image[pixel_index as usize] = pixel_color;
+        }
+    }
+}

enkou-shaders/src/entry/mod.rs

@@ -0,0 +1,4 @@
+//! # Entry
+//!
+//! Entry points for Enkou shaders
+pub mod image_accumulate;

enkou-shaders/src/image.rs

@@ -0,0 +1,155 @@
+//! Image
+
+use bytemuck::{Pod, Zeroable};
+use glam::{IVec2, UVec2, Vec4};
+use libm::floorf;
+
+/// Blending modes for mapping IFS color values (which are on a scale `[0, 1]`)
+/// to RGBA colors.
+#[derive(Copy, Clone, Default)]
+#[repr(u32)]
+pub enum BlendMode {
+    /// Map IFS color values to a linear blend of the nearest two palette colors
+    #[default]
+    Linear = 0,
+
+    /// Map IFS color values to the nearest single palette color
+    Step = 1,
+}
+
+impl BlendMode {
+    /// Map an IFS color value to RGBA color from the provided palette.
+    pub fn ifs_to_rgb(&self, color: f32, palette: &[Vec4]) -> Vec4 {
+        let colors_m_one = palette.len() - 1;
+        let period = 1.0 / colors_m_one as f32;
+        let index_lower = floorf(color / period) as usize;
+        let index_upper = (index_lower + 1).clamp(0, colors_m_one);
+        let rem = color % period / period;
+
+        match self {
+            BlendMode::Linear => palette[index_lower].lerp(palette[index_upper], rem),
+            BlendMode::Step => palette[index_lower],
+        }
+    }
+}
+
+// UNSAFE: Sound because enum has guaranteed layout (u32) and defined zero-value
+unsafe impl bytemuck::Zeroable for BlendMode {}
+// UNSAFE: Sound because enum has guaranteed layout (u32) and defined zero-value
+unsafe impl bytemuck::Pod for BlendMode {}
+
+/// Settings to use for mapping the IFS coordinates to an output image
+#[derive(Copy, Clone, Pod, Zeroable)]
+#[repr(C)]
+pub struct ImageSettings {
+    blend_mode: BlendMode,
+    dimensions: UVec2,
+}
+
+impl ImageSettings {
+    /// Create a new settings object
+    pub fn new(blend_mode: BlendMode, dimensions: UVec2) -> Self {
+        ImageSettings {
+            blend_mode,
+            dimensions,
+        }
+    }
+
+    /// Map a point from camera coordinates to pixel coordinates,
+    /// and check that the result is within the provided image dimensions.
+    pub fn transform_point_to_image(&self, point: IVec2) -> Option<UVec2> {
+        if 0 <= point.x
+            && (point.x as u32) < self.dimensions.x
+            && 0 <= point.y
+            && (point.y as u32) < self.dimensions.y
+        {
+            Some(point.as_uvec2())
+        } else {
+            None
+        }
+    }
+
+    /// Map a point from camera coordinates to a final pixel index
+    pub fn transform_point_to_index(&self, point: IVec2) -> Option<u32> {
+        self.transform_point_to_image(point)
+            .map(|pixel| self.dimensions.with_x(1).dot(pixel))
+    }
+
+    /// Map an IFS color coordinate to the palette RGB value
+    pub fn transform_color(&self, color: f32, palette: &[Vec4]) -> Vec4 {
+        self.blend_mode.ifs_to_rgb(color, palette)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::image::{BlendMode, ImageSettings};
+    use glam::{Vec4, ivec2, uvec2};
+
+    #[test]
+    fn blend_linear() {
+        let ifs_to_rgb = |color, palette| BlendMode::Linear.ifs_to_rgb(color, palette);
+
+        let palette = &[Vec4::splat(0.0), Vec4::splat(1.0)];
+        assert_eq!(ifs_to_rgb(0.0, palette), Vec4::splat(0.0));
+        assert_eq!(ifs_to_rgb(0.5, palette), Vec4::splat(0.5));
+        assert_eq!(ifs_to_rgb(1.0, palette), Vec4::splat(1.0));
+
+        let palette = &[Vec4::splat(1.0), Vec4::splat(2.0), Vec4::splat(3.0)];
+        assert_eq!(ifs_to_rgb(0.0, palette), Vec4::splat(1.0));
+        assert_eq!(ifs_to_rgb(0.5, palette), Vec4::splat(2.0));
+        assert_eq!(ifs_to_rgb(1.0, palette), Vec4::splat(3.0));
+
+        let palette = &[
+            Vec4::splat(1.0),
+            Vec4::splat(2.0),
+            Vec4::splat(3.0),
+            Vec4::splat(4.0),
+        ];
+        assert_eq!(ifs_to_rgb(0.0, palette), Vec4::splat(1.0));
+        assert_eq!(ifs_to_rgb(0.5, palette), Vec4::splat(2.5));
+        assert_eq!(ifs_to_rgb(1.0, palette), Vec4::splat(4.0));
+    }
+
+    #[test]
+    fn blend_step() {
+        let ifs_to_rgb = |color, palette| BlendMode::Step.ifs_to_rgb(color, palette);
+
+        let palette = &[Vec4::splat(0.0), Vec4::splat(1.0)];
+        assert_eq!(ifs_to_rgb(0.5, palette), Vec4::splat(0.0));
+
+        let palette = &[Vec4::splat(1.0), Vec4::splat(2.0), Vec4::splat(3.0)];
+        assert_eq!(ifs_to_rgb(0.0, palette), palette[0]);
+        assert_eq!(ifs_to_rgb(0.25, palette), palette[0]);
+        assert_eq!(ifs_to_rgb(0.4, palette), palette[0]);
+        assert_eq!(ifs_to_rgb(0.5, palette), palette[1]);
+        assert_eq!(ifs_to_rgb(0.7, palette), palette[1]);
+        assert_eq!(ifs_to_rgb(1.0, palette), palette[2]);
+    }
+
+    #[test]
+    fn image_bounds() {
+        let image_settings = ImageSettings::new(BlendMode::Linear, uvec2(100, 100));
+
+        assert!(
+            image_settings
+                .transform_point_to_image(ivec2(-1, -1))
+                .is_none()
+        );
+        assert!(
+            image_settings
+                .transform_point_to_image(ivec2(0, 0))
+                .is_some()
+        );
+        assert!(
+            image_settings
+                .transform_point_to_image(ivec2(99, 99))
+                .is_some()
+        );
+        assert!(
+            image_settings
+                .transform_point_to_image(ivec2(100, 100))
+                .is_none()
+        );
+    }
+}

enkou-shaders/src/lib.rs

@@ -1,10 +1,16 @@
 //! # Enkou
 #![no_std]
-#![deny(missing_docs)]
-#![allow(clippy::needless_range_loop)] // SPIR-V backend has issues with iteration over items
+#![warn(missing_docs)]
+// SPIR-V backend has issues with iteration over items:
+#![allow(clippy::needless_range_loop)]
+#![allow(clippy::manual_memcpy)]
+// Shader entry points are expected to have a lot of arguments:
+#![allow(clippy::too_many_arguments)]
 
 pub mod camera;
 pub mod chaos_game;
+pub mod entry;
+pub mod image;
 mod rng;
 pub mod transform;
 pub mod variation;

enkou-shaders/src/rng.rs

@@ -14,6 +14,8 @@ use rand_xoshiro::Xoshiro256StarStar;
 /// 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.
+// Temporarily unused, will be required once the main image accumulation entry point is implemented
+#[allow(unused)]
 pub(crate) fn xoshiro256starstar_from_seed(
     rng_state: <Xoshiro256StarStar as SeedableRng>::Seed,
 ) -> Xoshiro256StarStar {

enkou-shaders/src/transform.rs

@@ -5,7 +5,7 @@
 //! but produce more interesting images once we add variations.
 use crate::variation::Variation;
 use bytemuck::{Pod, Zeroable};
-use glam::{Affine2, UVec2, Vec2};
+use glam::{Affine2, FloatExt, UVec2, Vec2};
 use rand::Rng;
 
 /// Affine transform for use in the [`chaos_game`](crate::chaos_game).
@@ -15,15 +15,22 @@ pub struct Transform {
     coefficients: Affine2,
     coefficients_post: Affine2,
     variation_range: UVec2,
+    color: Vec2,
 }
 
 impl Transform {
     /// Create a new transform from an affine transformation matrix
-    pub fn new(coefficients: Affine2, coefficients_post: Affine2, variation_range: UVec2) -> Self {
+    pub fn new(
+        coefficients: Affine2,
+        coefficients_post: Affine2,
+        variation_range: UVec2,
+        color: Vec2,
+    ) -> Self {
         Transform {
             coefficients,
             coefficients_post,
             variation_range,
+            color,
         }
     }
 
@@ -47,6 +54,11 @@ impl Transform {
 
         self.coefficients_post.transform_point2(point)
     }
+
+    /// Apply this transform to a color
+    pub fn transform_color(&self, color: f32) -> f32 {
+        color.lerp(self.color.x, self.color.y)
+    }
 }
 
 #[cfg(test)]
@@ -54,7 +66,7 @@ mod test {
     use crate::rng::xoshiro256starstar_from_seed;
     use crate::transform::Transform;
     use crate::variation::{Variation, VariationKind};
-    use glam::{Affine2, uvec2, vec2};
+    use glam::{Affine2, Vec2, uvec2, vec2};
 
     #[test]
     fn transform_scaling() {
@@ -63,6 +75,7 @@ mod test {
             Affine2::from_scale(scale_coefficients),
             Affine2::IDENTITY,
             uvec2(0, 1),
+            Vec2::ZERO,
         );
 
         let mut rng = xoshiro256starstar_from_seed([0; 32]);
@@ -78,11 +91,17 @@ mod test {
     #[test]
     fn transform_scaling_post() {
         let scale_coefficients = vec2(2.0, 0.5);
-        let transform_pdj = Transform::new(Affine2::IDENTITY, Affine2::IDENTITY, uvec2(0, 1));
+        let transform_pdj = Transform::new(
+            Affine2::IDENTITY,
+            Affine2::IDENTITY,
+            uvec2(0, 1),
+            Vec2::ZERO,
+        );
         let transform_pdj_post = Transform::new(
             Affine2::IDENTITY,
             Affine2::from_scale(scale_coefficients),
             uvec2(0, 1),
+            Vec2::ZERO,
         );
 
         let mut rng = xoshiro256starstar_from_seed([0; 32]);
@@ -94,4 +113,23 @@ mod test {
 
         assert_eq!(point_pdj * scale_coefficients, point_pdj_post);
     }
+
+    #[test]
+    fn transform_color() {
+        // Color 0.5, color speed 1.0, so color value will always be 0.5 after transform
+        let color = vec2(0.5, 1.0);
+        let transform = Transform::new(Affine2::IDENTITY, Affine2::IDENTITY, uvec2(0, 1), color);
+
+        assert_eq!(transform.transform_color(0.0), 0.5);
+        assert_eq!(transform.transform_color(1.0), 0.5);
+        assert_eq!(transform.transform_color(2.0), 0.5);
+
+        // Color 1.0, color speed 0.5, so color value moves to halfway between current and 1.0
+        let color = vec2(1.0, 0.5);
+        let transform = Transform::new(Affine2::IDENTITY, Affine2::IDENTITY, uvec2(0, 1), color);
+
+        assert_eq!(transform.transform_color(0.0), 0.5);
+        assert_eq!(transform.transform_color(1.0), 1.0);
+        assert_eq!(transform.transform_color(2.0), 1.5);
+    }
 }