Generate random grass texture

Description

Instead of hard coding a 2x2 array, generate an array of random bytes for an 8x8 texture. We're still using gl::GREEN when uploading our texture data, so the random values might look like a poor quality grass texture (if you squint hard enough).

For random values there's the rand crate, but I was curious how random numbers work so I implemented my own. This implementation is a xorshift random number generator which is very simple to implement.

When we add more randomness later, we'll likely switch to the rand crate which is far more robust.

Screenshot

Commands

git clone git@github.com:atsheehan/iridium
cd iridium
git checkout 828b084bdecc26456c04e209e658a4378dbd35e5
cargo run --release

Code Changes

`Modified src/math.rsGitHub`

@@ -1 +1,23 @@
11  pub(crate) struct Vec3(pub(crate) f32, pub(crate) f32, pub(crate) f32);
2+ 
3+ pub(crate) struct RandomNumberGenerator {
4+     seed: u32,
5+ }
6+ 
7+ impl RandomNumberGenerator {
8+     pub(crate) fn with_seed(seed: u32) -> Self {
9+         Self { seed }
10+     }
11+ 
12+     pub(crate) fn gen_u32(&mut self) -> u32 {
13+         self.seed ^= self.seed << 13;
14+         self.seed ^= self.seed >> 17;
15+         self.seed ^= self.seed << 5;
16+         self.seed
17+     }
18+ 
19+     pub(crate) fn gen_range(&mut self, min: u32, max: u32) -> u32 {
20+         let range = max - min;
21+         min + self.gen_u32() % range
22+     }
23+ }

@@ -1 +1,23 @@
1  pub(crate) struct Vec3(pub(crate) f32, pub(crate) f32, pub(crate) f32);

@@ -1 +1,23 @@
1  pub(crate) struct Vec3(pub(crate) f32, pub(crate) f32, pub(crate) f32);
2+ 
3+ pub(crate) struct RandomNumberGenerator {
4+     seed: u32,
5+ }
6+ 
7+ impl RandomNumberGenerator {
8+     pub(crate) fn with_seed(seed: u32) -> Self {
9+         Self { seed }
10+     }
11+ 
12+     pub(crate) fn gen_u32(&mut self) -> u32 {
13+         self.seed ^= self.seed << 13;
14+         self.seed ^= self.seed >> 17;
15+         self.seed ^= self.seed << 5;
16+         self.seed
17+     }
18+ 
19+     pub(crate) fn gen_range(&mut self, min: u32, max: u32) -> u32 {
20+         let range = max - min;
21+         min + self.gen_u32() % range
22+     }
23+ }

`Modified src/render.rsGitHub`

@@ -18,7 +18,7 @@
1818      window::{Window, WindowBuilder, WindowId},
1919  };
2020  
21- use crate::math::Vec3;
21+ use crate::math::{RandomNumberGenerator, Vec3};
2222  
2323  const CUBE_VERTEX_SHADER_SRC: &str = include_str!("../shaders/cube.vert");
2424  const CUBE_FRAGMENT_SHADER_SRC: &str = include_str!("../shaders/cube.frag");
@@ -87,18 +87,17 @@
8787              gl::GenTextures(1, &mut cube_texture_id);
8888              gl::BindTexture(gl::TEXTURE_2D, cube_texture_id);
8989  
90-             const TEXTURE_WIDTH: usize = 2;
91-             const TEXTURE_HEIGHT: usize = 2;
90+             const TEXTURE_WIDTH: usize = 8;
91+             const TEXTURE_HEIGHT: usize = 8;
9292              const VALUES_PER_PIXEL: usize = 3;
9393              const TEXTURE_SIZE: usize = TEXTURE_WIDTH * TEXTURE_HEIGHT * VALUES_PER_PIXEL;
9494  
95-             #[rustfmt::skip]
96-             let data: [u8; TEXTURE_SIZE] = [
97-                 252, 244, 183,
98-                 137, 233, 51,
99-                 117, 21, 246,
100-                 157, 12, 112
101-             ];
95+             let mut rng = RandomNumberGenerator::with_seed(42);
96+             let mut data: Vec<u8> = Vec::with_capacity(TEXTURE_SIZE);
97+ 
98+             for _ in 0..TEXTURE_SIZE {
99+                 data.push(rng.gen_range(120, 180) as u8);
100+             }
102101  
103102              gl::TexImage2D(
104103                  gl::TEXTURE_2D,

@@ -18,7 +18,7 @@
18      window::{Window, WindowBuilder, WindowId},
19  };
20  
21- use crate::math::Vec3;
22  
23  const CUBE_VERTEX_SHADER_SRC: &str = include_str!("../shaders/cube.vert");
24  const CUBE_FRAGMENT_SHADER_SRC: &str = include_str!("../shaders/cube.frag");
@@ -87,18 +87,17 @@
87              gl::GenTextures(1, &mut cube_texture_id);
88              gl::BindTexture(gl::TEXTURE_2D, cube_texture_id);
89  
90-             const TEXTURE_WIDTH: usize = 2;
91-             const TEXTURE_HEIGHT: usize = 2;
92              const VALUES_PER_PIXEL: usize = 3;
93              const TEXTURE_SIZE: usize = TEXTURE_WIDTH * TEXTURE_HEIGHT * VALUES_PER_PIXEL;
94  
95-             #[rustfmt::skip]
96-             let data: [u8; TEXTURE_SIZE] = [
97-                 252, 244, 183,
98-                 137, 233, 51,
99-                 117, 21, 246,
100-                 157, 12, 112
101-             ];
102  
103              gl::TexImage2D(
104                  gl::TEXTURE_2D,

@@ -18,7 +18,7 @@
18      window::{Window, WindowBuilder, WindowId},
19  };
20  
21+ use crate::math::{RandomNumberGenerator, Vec3};
22  
23  const CUBE_VERTEX_SHADER_SRC: &str = include_str!("../shaders/cube.vert");
24  const CUBE_FRAGMENT_SHADER_SRC: &str = include_str!("../shaders/cube.frag");
@@ -87,18 +87,17 @@
87              gl::GenTextures(1, &mut cube_texture_id);
88              gl::BindTexture(gl::TEXTURE_2D, cube_texture_id);
89  
90+             const TEXTURE_WIDTH: usize = 8;
91+             const TEXTURE_HEIGHT: usize = 8;
92              const VALUES_PER_PIXEL: usize = 3;
93              const TEXTURE_SIZE: usize = TEXTURE_WIDTH * TEXTURE_HEIGHT * VALUES_PER_PIXEL;
94  
95+             let mut rng = RandomNumberGenerator::with_seed(42);
96+             let mut data: Vec<u8> = Vec::with_capacity(TEXTURE_SIZE);
97+ 
98+             for _ in 0..TEXTURE_SIZE {
99+                 data.push(rng.gen_range(120, 180) as u8);
100+             }
 
101  
102              gl::TexImage2D(
103                  gl::TEXTURE_2D,