add 'mass' and 'elasticity' entity properties

src/content/loading/EntityLoader.cpp

@@ -89,5 +89,7 @@ template<> void ContentUnitLoader<EntityDef>::loadUnit(
     root.at("skeleton-name").get(def.skeletonName);
     root.at("blocking").get(def.blocking);
     root.at("solid").get(def.solid);
+    root.at("mass").get(def.mass);
+    root.at("elasticity").get(def.elasticity);
     root.at("step-height").get(def.stepHeight);
 }

src/objects/Entities.cpp

@@ -22,6 +22,7 @@
 
 #include <entt/entity/registry.hpp>
 #include <glm/ext/matrix_transform.hpp>
+#include <limits>
 #include <sstream>
 
 static debug::Logger logger("entities");
@@ -318,6 +319,9 @@ void Entities::preparePhysics(float delta) {
         if (!eid.def.solid) {
             continue;
         }
+        rigidbody.hitbox.mass = eid.def.bodyType == BodyType::DYNAMIC
+                                    ? eid.def.mass
+                                    : std::numeric_limits<float>::infinity();
         solidHitboxes.emplace_back(&rigidbody.hitbox);
     }
 }

src/objects/EntityDef.cpp

@@ -10,6 +10,8 @@ void EntityDef::cloneTo(EntityDef& dst) {
     dst.skeletonName = skeletonName;
     dst.blocking = blocking;
     dst.solid = solid;
+    dst.mass = mass;
+    dst.elasticity = elasticity;
     dst.stepHeight = stepHeight;
     dst.save = save;
 }

src/objects/EntityDef.hpp

@@ -45,6 +45,12 @@ struct EntityDef {
     /// @brief Is the entity solid (blocks other entities)
     bool solid = false;
 
+    /// @brief Mass for physics calculations
+    float mass = 1.0f;
+
+    /// @brief Elasticity for physics calculations
+    float elasticity = 0.0f;
+
     /// @brief Max obstacle height that does not require jumping
     float stepHeight = 0.5f;
 

src/physics/PhysicsSolver.cpp

@@ -26,6 +26,12 @@ static glm::vec3 calc_collsion_velocity_result(
 ) {
     const auto& vA = a.velocity;
     const auto& vB = b.velocity;
+    if (glm::isinf(a.mass)) {
+        return vA;
+    }
+    if (glm::isinf(b.mass)) {
+        return vA * -a.elasticity + vB;
+    }
     const auto& mA = a.mass;
     const auto& mB = b.mass;
     return (mA * vA + mB * vB + a.elasticity * mB * (vB - vA)) / (mA + mB);