upd: diffuse material

1 files changed, 37 insertions, 0 deletions

diff --git a/src/calculus.rs b/src/calculus.rs
index a39c8a5..8865154 100644
--- a/src/calculus.rs
+++ b/src/calculus.rs
@@ -16,6 +16,43 @@ pub mod calculus {
             Self { x, y, z }
         }
 
+        fn random() -> Self {
+            let mut rng = rand::rng();
+            Self::new(
+                rng.random(),
+                rng.random(),
+                rng.random(),
+            )
+        }
+
+        fn random_range(min: f32, max: f32) -> Self {
+            let mut rng = rand::rng();
+            Self::new(
+                rng.random_range(min..max),
+                rng.random_range(min..max),
+                rng.random_range(min..max),
+            )
+        }
+
+        fn random_unit() -> Vec3 {
+            loop {
+                let p = Self::random_range(-1.0, 1.0);
+                let lensq = p.mag_sqr();
+                if f32::EPSILON < lensq && lensq <= 1.0 {
+                    return p.scalar_mul(1.0 / lensq.sqrt())
+                }
+            }
+        }
+
+        pub fn random_on_hemisphere(normal: &Vec3) -> Vec3 {
+            let on_unit_sphere = Self::random_unit();
+            if on_unit_sphere.dot_prod(normal) > 0.0 {
+                on_unit_sphere
+            } else {
+                on_unit_sphere.scalar_mul(-1.0)
+            }
+        }
+
         pub fn add(&self, other: &Self) -> Self {
             Self {
                 x: self.x + other.x,