Add basic math module

src/main.rs

@@ -1,4 +1,5 @@
 mod core;
+mod math;
 mod render;
 mod voxel;
 

src/math.rs

@@ -0,0 +1,32 @@
+/// Linear interpolation.
+pub fn lerp(a: f32, b: f32, w: f32) -> f32 {
+    assert!(0.0 <= w && w <= 1.0);
+    a + (b - a) * w
+}
+
+/// Bilinear interpolation.
+/// Expected order of `p` is from a nested `for` loop with the outer loop being `y`.
+/// `w` is expected to be `[wx, wy]`
+pub fn bi_lerp(p: &[f32], w: &[f32]) -> f32 {
+    assert_eq!(p.len(), 4);
+    assert_eq!(w.len(), 2);
+
+    lerp(lerp(p[0], p[1], w[0]), lerp(p[2], p[3], w[0]), w[1])
+}
+
+/// Trilinear interpolation.
+/// Expected order of `p` is from a nested `for` loop with the outer loop being `z`.
+/// `w` is expected to be `[wx, wy, wz]`.
+pub fn tri_lerp(p: &[f32], w: &[f32]) -> f32 {
+    assert_eq!(p.len(), 8);
+    assert_eq!(w.len(), 3);
+
+    let front = bi_lerp(&[p[0], p[1], p[2], p[3]], &[w[0], w[1]]);
+    let back = bi_lerp(&[p[4], p[5], p[6], p[7]], &[w[0], w[1]]);
+    lerp(front, back, w[2])
+}
+
+/// Maps a 3d index to a 1d index
+pub fn to_1d_index(p: glam::UVec3, dim: glam::UVec3) -> usize {
+    (p.x + p.y * dim.x + p.z * dim.x * dim.y) as usize
+}