upd hit intersection simplified

1 files changed, 6 insertions, 5 deletions

diff --git a/src/renderer.rs b/src/renderer.rs
index d27edb4..49d8046 100644
--- a/src/renderer.rs
+++ b/src/renderer.rs
@@ -14,6 +14,7 @@ fn ray_color(ray: &Ray) -> Color {
             normal.z + 1.0,
         ).mul_scalar(0.5);
     }
+
     let unit_direction = ray.direction.unit();
     let a = 0.5 * (unit_direction.y + 1.0);
     let color1 = Color::new(1.0, 1.0, 1.0).mul_scalar(1.0 - a);
@@ -23,14 +24,14 @@ fn ray_color(ray: &Ray) -> Color {
 
 fn hit_sphere(center: &Point3, radius: f32, ray: &Ray) -> f32 {
     let oc = center.sub(&ray.origin);
-    let a = ray.direction.dot_prod(&ray.direction);
-    let b = -2.0 * ray.direction.dot_prod(&oc);
-    let c  = oc.dot_prod(&oc) - radius * radius;
-    let discriminant = b * b - 4.0 * a * c;
+    let a = ray.direction.mag_sqr();
+    let h = ray.direction.dot_prod(&oc);
+    let c  = oc.mag_sqr() - radius * radius;
+    let discriminant = h * h - a * c;
     if discriminant < 0.0 {
         -1.0
     } else {
-        (-b - discriminant.sqrt()) / (2.0 * a)
+        (h - discriminant.sqrt()) / a
     }
 }