Fixed raycast sphere.

src/dawn/physics/3d/Ray3D.cpp

@@ -14,20 +14,23 @@ bool_t Dawn::raytestSphere(
   glm::vec3 *normal,
   float_t *distance
 ) {
-  assertNotNull(hit);
-  assertNotNull(normal);
+  float_t a = glm::dot(ray.direction, ray.direction);
+  float_t b = 2.0f * glm::dot(ray.direction, ray.origin - sphere.center);
+  float_t c = glm::dot(ray.origin - sphere.center, ray.origin - sphere.center);
+  c -= sphere.radius * sphere.radius;
 
-  glm::vec3 h, n;
-  auto result = glm::intersectRaySphere(
-    ray.origin, ray.direction,
-    sphere.center, sphere.radius,
-    h, n
-  );
-  if(!result) return result;
-  *hit = h;
-  *normal = n;
-  *distance = glm::distance(ray.origin, h);
-  return result;
+  float_t dt = b * b - 4.0f * a * c;
+  if(dt < 0.0f) return false;
+
+  float_t t0 = (-b - sqrtf(dt)) / (a * 2.0f);
+  if(t0 < 0.0f) return false;
+
+  *hit = ray.origin + t0 * ray.direction;
+  *normal = glm::normalize(*hit - sphere.center);
+  *distance = t0;
+
+
+  return true;
 }
 
 bool_t Dawn::raytestTriangle(