upd camera focus

1 files changed, 14 insertions, 0 deletions

diff --git a/src/calculus.rs b/src/calculus.rs
index e59ae56..62253cf 100644
--- a/src/calculus.rs
+++ b/src/calculus.rs
@@ -132,6 +132,20 @@ pub mod calculus {
             let r_out_parallel = normal.scalar_mul(-1.0 * f);
             r_out_perp.add(&r_out_parallel)
         }
+
+        pub fn random_in_unit_disk() -> Self {
+            let mut rng = rand::rng();
+            loop {
+                let p = Vec3::new(
+                    rng.random_range(-1.0..1.0),
+                    rng.random_range(-1.0..1.0),
+                    0.0
+                );
+                if p.mag_sqr() < 1.0 {
+                    return p;
+                }
+            }
+        }
     }
 
     pub struct Ray {