X-Git-Url: https://git.rohieb.name/MicroTrace.git/blobdiff_plain/0e3446ceb6fd6db0cb292671f37b46daaa2aed5b..0b29fae9afb220c13cc0c48c91031f0798b91ec7:/Sphere.cxx

diff --git a/Sphere.cxx b/Sphere.cxx
index 3c19afa..77d4320 100644
--- a/Sphere.cxx
+++ b/Sphere.cxx
@@ -1,7 +1,7 @@
 #include "Sphere.hxx"
 
 Sphere::Sphere(const Vec3f& center, float radius, Shader* shader)
-  : Primitive(shader), 
+  : Primitive(shader),
     m_center(center),
     m_radius(radius)
 {
@@ -20,12 +20,12 @@ Sphere::Intersect(Ray& ray)
 
   if( B*B-4*A*C < 0 )
     return false;
-  
+
   float root = sqrtf(B*B-4*A*C);
   float t = (-B-root)/(2.0f*A);
   if(t > ray.t())
     return false;
-      
+
   if( t < 1e-6 )
     {
       t = (-B+root)/(2.0f*A);
@@ -39,5 +39,20 @@ Sphere::Intersect(Ray& ray)
 Vec3f
 Sphere::GetNormal(Ray& ray)
 {
-  return Vec3f();
+  // We don't want to modify the ray (probably this is not needed, but I am
+  // too lazy to think about it now ...)
+  Ray tempRay = ray;
+
+  // Surface normal is the difference between intersection and center point
+  if(Intersect(tempRay)) {
+    // intersection point
+    Vec3f i = tempRay.origin() + tempRay.direction() * (tempRay.t() - Epsilon);
+    // normal
+    Vec3f n = (i - m_center);
+    n.normalize();
+    return n;
+  } else {
+    // no intersection with ray, so no surface normal
+    return Vec3f(0,0,0);
+  }
 }