better stability of collision response

diff --git a/src/world/world.cpp b/src/world/world.cpp
index 349b82d00233e5d67fe3d6a6a1d7aa3f178ffde3..8f22f0c091645486c99913cfa4925bdc1533e5be 100644 (file)
--- a/src/world/world.cpp
+++ b/src/world/world.cpp
@@ -468,14 +468,28 @@ glm::vec3 World::CollisionForce(
                        min_pen = min(min_pen, local_pen);
                        max_pen = max(max_pen, local_pen);
                }
-               glm::vec3 penetration(min_pen + max_pen);
-               glm::vec3 normal(normalize(penetration) * -1.0f);
+               glm::vec3 correction(0.0f);
+               // only apply correction for axes where penetration is only in one direction
+               for (std::size_t i = 0; i < 3; ++i) {
+                       if (min_pen[i] < -std::numeric_limits<float>::epsilon()) {
+                               if (max_pen[i] < std::numeric_limits<float>::epsilon()) {
+                                       correction[i] = -min_pen[i];
+                               }
+                       } else {
+                               correction[i] = -max_pen[i];
+                       }
+               }
+               // correction may be zero in which case normalize() returns NaNs
+               if (dot(correction, correction) < std::numeric_limits<float>::epsilon()) {
+                       return glm::vec3(0.0f);
+               }
+               glm::vec3 normal(normalize(correction));
                glm::vec3 normal_velocity(normal * dot(state.velocity, normal));
                // apply force proportional to penetration
                // use velocity projected onto normal as damper
                constexpr float k = 1000.0f; // spring constant
-               constexpr float b = 100.0f; // damper constant
-               const glm::vec3 x(penetration); // endpoint displacement from equilibrium in m
+               constexpr float b = 10.0f; // damper constant
+               const glm::vec3 x(-correction); // endpoint displacement from equilibrium in m
                const glm::vec3 v(normal_velocity); // relative velocity between endpoints in m/s
                return (((-k) * x) - (b * v)); // times 1kg/s, in kg*m/s²
        } else {