Add entry points for GPU

enkou-shaders/src/chaos_game.rs

@@ -12,16 +12,17 @@
 //!
 //! 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 glam::{Vec2, vec2};
-use rand::distr::{Distribution, StandardUniform};
-use rand::{Rng, RngExt};
+use rand::Rng;
+use rand::distributions::{Distribution, Standard};
+use spirv_std::glam::{Vec2, vec2};
 
 struct BiUnit;
 impl Distribution<f32> for BiUnit {
     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f32 {
-        rng.sample::<f32, _>(StandardUniform) * 2.0 - 1.0
+        rng.sample::<f32, _>(Standard) * 2.0 - 1.0
     }
 }
 
@@ -40,11 +41,11 @@ pub fn step_chaos_game<R: Rng>(
     weights: &[f32],
     variations: &[Variation],
 ) -> (Vec2, u32) {
-    let mut choice_weight = rng.sample::<f32, _>(StandardUniform);
+    let mut choice_weight = rng.sample::<f32, _>(Standard);
     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;
         }
@@ -105,3 +106,40 @@ impl<'a, R: Rng> Iterator for ChaosGame<'a, R> {
         Some(next_point)
     }
 }
+
+pub mod entry {
+    use crate::chaos_game::ChaosGame;
+    use crate::transform::Transform;
+    use crate::variation::Variation;
+    use glam::Vec2;
+    use rand_xoshiro::Xoshiro256StarStar;
+    use spirv_std::spirv;
+
+    fn xoshiro_from_state(rng_state: [u8; 32]) -> Xoshiro256StarStar {
+        let mut rng_state_actual = [1u64, 2u64, 3u64, 4u64];
+        unsafe { core::mem::transmute(rng_state_actual) }
+    }
+
+    #[spirv(compute(entry_point_name = "main_chaos_game", threads(1)))]
+    pub extern "C" 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();
+        }
+    }
+}