sphere/sphere intersection test

[gong.git] / src / geometry / geometry.cpp

diff --git a/src/geometry/geometry.cpp b/src/geometry/geometry.cpp
index 002c68f0d1ba69760b65d41049e069a2ef2d490a..1d7beeb20777747d500bbebf3e6a1300f60f1fee 100644 (file)
--- a/src/geometry/geometry.cpp
+++ b/src/geometry/geometry.cpp
@@ -302,6 +302,31 @@ std::ostream &operator <<(std::ostream &out, const Sphere &s) {
        return out << "Sphere(" << s.origin << ", " << s.radius << ')';
 }
 
+bool Intersection(
+       const Sphere &a,
+       const Sphere &b,
+       float &dist,
+       glm::vec3 &norm
+) noexcept {
+       glm::vec3 diff(b.origin - a.origin);
+       float dist2 = glm::length2(diff);
+       if (dist2 < std::numeric_limits<float>::epsilon()) {
+               // origins coincide, use smaller of the diameters for
+               // depth and pick arbitrary normal
+               dist = 2.0f * std::min(a.radius, b.radius);
+               norm = glm::vec3(1.0f, 0.0f, 0.0f);
+               return true;
+       }
+       if (dist2 < (a.radius + b.radius) * (a.radius + b.radius)) {
+               dist = std::sqrt(dist2);
+               norm = diff / dist;
+               dist = a.radius - (dist - b.radius);
+               return true;
+       } else {
+               return false;
+       }
+}
+
 bool Intersection(
        const Sphere &sphere,
        const Plane &plane,