UCA Game Physics & Animation 3 — Questions and Answers
Question 1: Which component would you add to a GameObject to simulate cloth physics in Unity?
- Rigidbody
- Cloth (Correct answer)
- Joint
- Soft Body
Correct answer: Cloth
Unity's Cloth component simulates cloth-like physics on a mesh, responding to forces and colliders.
Question 2: What is the role of a Physics Material (PhysicMaterial) in Unity?
- It defines the shader used on a collider
- It sets friction and bounciness properties for collision surfaces (Correct answer)
- It controls Rigidbody mass
- It determines layer collision rules
Correct answer: It sets friction and bounciness properties for collision surfaces
A PhysicMaterial stores friction (static/dynamic) and bounciness (restitution) values that affect how colliders interact.
Question 3: What does 'Root Motion' refer to in Unity animation?
- The root bone's rotation being locked
- Movement of the GameObject driven by animation clip motion data rather than code (Correct answer)
- The first frame of every animation clip
- Physics-based procedural movement
Correct answer: Movement of the GameObject driven by animation clip motion data rather than code
Root Motion lets the animation clip itself move the character's Transform, using baked displacement data from the animator.
Question 4: Which type of Joint constrains two Rigidbodies so they maintain a fixed distance apart, like a rod?
- Hinge Joint
- Spring Joint (Correct answer)
- Fixed Joint
- Character Joint
Correct answer: Spring Joint
A Spring Joint keeps two Rigidbodies at approximately a set distance using spring forces, though a ConfigurableJoint with locked linear limits acts as a true rigid rod.
Question 5: In Unity's Animator, what is an 'Avatar Mask' used for?
- Hiding characters in multiplayer
- Restricting which body parts are affected by a specific animation layer (Correct answer)
- Blending two Animator Controllers
- Disabling root motion on certain bones
Correct answer: Restricting which body parts are affected by a specific animation layer
An Avatar Mask lets you specify which skeleton bones an Animator layer applies to, enabling upper/lower body animation separation.
Question 6: What does FixedUpdate's execution timing guarantee in Unity?
- It runs once per rendered frame
- It runs at a consistent physics time step independent of frame rate (Correct answer)
- It runs only when a collision occurs
- It runs after all Update calls finish
Correct answer: It runs at a consistent physics time step independent of frame rate
FixedUpdate is called at a fixed interval defined in Time.fixedDeltaTime, making it ideal for physics calculations that need frame-rate independence.
Question 7: Which Animator Controller feature allows you to store and reuse sets of transitions and states across multiple controllers?
- Sub-State Machine (Correct answer)
- Override Controller
- Blend Tree
- State Machine Behaviour
Correct answer: Sub-State Machine
A Sub-State Machine groups related states into a nested machine within an Animator Controller, improving organization and reuse.
UCA Game Physics & Animation 3
Which component would you add to a GameObject to simulate cloth physics in Unity?