allow clicking celestial bodies

[blobs.git] / src / math / geometry.cpp

diff --git a/src/math/geometry.cpp b/src/math/geometry.cpp
index 58c97ae71e378b98f14ce3cc1917ed8201e23aad..3afa944f479b0fc41905d5de6364ee6ca8068e5b 100644 (file)
--- a/src/math/geometry.cpp
+++ b/src/math/geometry.cpp
@@ -148,5 +148,37 @@ bool Intersect(
        return true;
 }
 
+bool Intersect(
+       const Ray &r,
+       const Sphere &s,
+       glm::dvec3 &normal,
+       double &dist
+) noexcept {
+       const glm::dvec3 diff(s.origin - r.Origin());
+       if (glm::dot(diff, r.Direction()) < 0.0) {
+               if (glm::length2(diff) > s.radius * s.radius) return false;
+               if (std::abs(glm::length2(diff) - s.radius * s.radius) < std::numeric_limits<double>::epsilon() * s.radius) {
+                       normal = glm::normalize(-diff);
+                       dist = 0.0;
+                       return true;
+               }
+               const glm::dvec3 pc(r.Direction() * glm::dot(r.Direction(), diff) + r.Origin());
+               double idist = std::sqrt(s.radius * s.radius - glm::length2(pc - s.origin));
+               dist = idist - glm::length(pc - r.Origin());
+               normal = glm::normalize((r.Origin() + (r.Direction() * dist)) - s.origin);
+               return true;
+       }
+       const glm::dvec3 pc(r.Direction() * glm::dot(r.Direction(), diff) + r.Origin());
+       if (glm::length2(s.origin - pc) > s.radius * s.radius) return false;
+       double idist = std::sqrt(s.radius * s.radius - glm::length2(pc - s.origin));
+       if (glm::length2(diff) > s.radius * s.radius) {
+               dist = glm::length(pc - r.Origin()) - idist;
+       } else {
+               dist = glm::length(pc - r.Origin()) + idist;
+       }
+       normal = glm::normalize((r.Origin() + (r.Direction() * dist)) - s.origin);
+       return true;
+}
+
 }
 }