Optimizing Physics Performance

The NVIDIA PhysX physics engineA system that simulates aspects of physical systems so that objects can accelerate correctly and be affected by collisions, gravity and other forces. More info
See in Glossary used by Unity is available on iOSApple’s mobile operating system. More info
See in Glossary but the performance limits of the hardware will be reached more easily on mobile platforms than desktops.

Here are some tips for tuning physics to get better performance on iOS:-

• You can adjust the Fixed TimestepA customizable framerate-independent interval that dictates when physics calculations and FixedUpdate() events are performed. More info
  See in Glossary setting (in the Time window) to reduce the time spent on physics updates. Increasing the timestep will reduce the CPU overhead at the expense of the accuracy of the physics. Often, lower accuracy is an acceptable tradeoff for increased speed.
• Set the Maximum Allowed Timestep in the Time window in the 8–10fps range to cap the time spent on physics in the worst case scenario.
• Mesh collidersA free-form collider component which accepts a mesh reference to define its collision surface shape. More info
  See in Glossary have a much higher performance overhead than primitive colliders, so use them sparingly. It is often possible to approximate the shape of a meshThe main graphics primitive of Unity. Meshes make up a large part of your 3D worlds. Unity supports triangulated or Quadrangulated polygon meshes. Nurbs, Nurms, Subdiv surfaces must be converted to polygons. More info
  See in Glossary by using child objects with primitive colliders. The child colliders will be controlled collectively as a single compound colliderAn invisible shape that is used to handle physical collisions for an object. A collider doesn’t need to be exactly the same shape as the object’s mesh - a rough approximation is often more efficient and indistinguishable in gameplay. More info
  See in Glossary by the rigidbodyA component that allows a GameObject to be affected by simulated gravity and other forces. More info
  See in Glossary on the parent.
• While wheel collidersA special collider for grounded vehicles. It has built-in collision detection, wheel physics, and a slip-based tire friction model. It can be used for objects other than wheels, but it is specifically designed for vehicles with wheels. More info
  See in Glossary are not strictly colliders in the sense of solid objects, they nonetheless have a high CPU overhead.

The total amount of physics calculation depends on the number of non-sleeping rigid bodies and colliders in the sceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary and the complexity of the colliders. You can keep track of how many physics objects there are in the scene using the internal profiler.