Don't set the player to previous position when uncrouching.

src/Engine/Collision/CollisionSystem.cpp

@@ -66,7 +66,7 @@ void CollisionSystem::UpdateComponent(EntityWrapper& entity, ComponentWrapper& c
                 }
             }
         }
-
+        bool& jitterGuard = (bool&)entity["Collidable"]["JitterGuard"];
         // Collide against octree items
         m_OctreeResult.clear();
         m_Octree->ObjectsInSameRegion(*boundingBox, m_OctreeResult);
@@ -93,7 +93,7 @@ void CollisionSystem::UpdateComponent(EntityWrapper& entity, ComponentWrapper& c
                 float verticalStepHeight = (float)(double)cPhysics["VerticalStepHeight"];
                 if (Collision::AABBvsTriangles(boxA, model->Vertices(), model->m_Indices, modelMatrix, inOutVelocity, verticalStepHeight, isOnGround, resolutionVector)) {
                     //Move the position to previous position if it is not moving in the xz-plane, else resolve with the resolution vector.
-                    (glm::vec3&)cTransform["Position"] += notMovingxz ? prevPosIt->second - boxA.Origin() : resolutionVector;
+                    (glm::vec3&)cTransform["Position"] += jitterGuard && notMovingxz ? prevPosIt->second - boxA.Origin() : resolutionVector;
                     boxA = *Collision::EntityAbsoluteAABB(entity);
                     cPhysics["Velocity"] = inOutVelocity;
                     if (isOnGround) {
@@ -118,6 +118,7 @@ void CollisionSystem::UpdateComponent(EntityWrapper& entity, ComponentWrapper& c
             (bool)cPhysics["IsOnGround"] = false;
         }
 
+        jitterGuard = true;
         m_PrevPositions[entity] = boxA.Origin();
     }
 }

src/Game/Systems/PlayerMovementSystem.cpp

@@ -273,6 +273,15 @@ void PlayerMovementSystem::updateMovementControllers(double dt)
                     size = glm::vec3(1.f, 1.f, 1.f);
                 } else {
                     size = glm::vec3(1.f, 1.6f, 1.f);
+                    if (controller->CrouchingLastFrame() && player.HasComponent("Collidable")) {
+                        // Disable jitter guard so player doesn't get stuck in the ground.
+                        (bool&)player["Collidable"]["JitterGuard"] = false;
+                        if (isOnGround) {
+                            // The collision should resolve this anyway, but 
+                            // this is more reliable, since the box gets larger.
+                            ((glm::vec3&)cTransform["Position"]).y += 0.3f;
+                        }
+                    }
                 }
             }