2 files changed, 24 insertions, 7 deletions
diff --git a/src/sample/mod.rs b/src/sample/mod.rs
index 6f2c3eb..84ac755 100644
--- a/src/sample/mod.rs
+++ b/src/sample/mod.rs
@@ -1,11 +1,33 @@
 use crate::Float;
-use crate::core::Vector2f;
+use crate::core::{Vector3f, Vector2f};
+use std::f32::consts::PI;
 
 mod uniform;
 
 pub use uniform::UniformSampler;
 
+fn distribute_between(x: Float, a: Float, b: Float) -> Float {
+    x * (b - a) + a
+}
+
 pub trait Sampler {
     fn get_sample(&mut self) -> Float;
-    fn get_sample_2d(&mut self) -> Vector2f;
+
+    fn get_sample_2d(&mut self) -> Vector2f {
+        Vector2f::new_xy(self.get_sample(), self.get_sample())
+    }
+
+    fn get_unit_vector(&mut self) -> Vector3f {
+        let s2d = self.get_sample_2d();
+
+        let lambda = distribute_between(s2d.x, -PI, PI);
+        let costheta = 2.0 * s2d.y - 1.0;
+        let sintheta = costheta.acos().sin();
+
+        Vector3f::new_xyz(
+            lambda.cos() * sintheta,
+            lambda.sin() * sintheta,
+            costheta,
+            )
+    }
 }
diff --git a/src/sample/uniform.rs b/src/sample/uniform.rs
index 221fdf8..cc6825a 100644
--- a/src/sample/uniform.rs
+++ b/src/sample/uniform.rs
@@ -1,4 +1,3 @@
-use crate::core::Vector2f;
 use crate::Float;
 use super::Sampler;
 
@@ -25,8 +24,4 @@ impl Sampler for UniformSampler {
     fn get_sample(&mut self) -> Float {
         self.d.sample(&mut self.r)
     }
-
-    fn get_sample_2d(&mut self) -> Vector2f {
-        Vector2f::new_xy(self.get_sample(), self.get_sample())
-    }
 }