Tutorial Physics: Unity Car

Transcription

1 Tutorial Physics: Unity Car This activity will show you how to create a free-driving car game using Unity from scratch. You will learn how to import models using FBX file and set texture. You will learn how to set physics to car model and add sound effect to the scene. More importantly, you will learn to add camera control script and car control script. Getting Started 1. Download FreeDriveCarProject from blackboard (Unity Week four). Unzip it to a folder. Open Project File -> Open Project. Unity will ask you to upgrade the project. Please accept it. 2. Download car model (FBX file) from Blackboard. Asset -> Import New Asset. Move car into Asset folder -> Artwork folder -> Car folder

2 3. Click the Car model in asset folder. Go to inspector window in the right. Change scale factor to 1.0 and set mesh compression to medium. Then click the apply button. 4. Add texture to the car model. Click the < in the right side of Car model to expand the geometry model. Select TruckBody in the last one in the list. In the inspector window, click select button in Main Color section. Select truck_color_normal texture from the list (in the bottom of the list).

3 4. Drag the car model to the hierarchy. Select the Car in the hierarchy window. Go to inspect window. Change position to 119, 0, 214. Change Scale to 0.004,0.004, Click Add Component button. Add Physics ->RigidBody. Change mass to Notice Car will drop like a stone as it is influenced by Gravity. We need to add colliders to prevent it to drop through terrain. 7. Add upper Car body collider. Menu GameObject-> Create Empty Game. Rename it as ColliderTop and Drag it under Car in Hierarchy window. Add Box Colliders using Add component in inspector windows. Adjust its size to fit with upper part of the car.

4 Remember use transform toolbar in the top to adjust size and position of box collider. 8. Add lower Car body collider. Menu GameObject-> Create Empty Game. Rename it as ColliderBottom and Drag it under Car in Hierarchy window. Add Box Colliders using Add component in inspector windows. Adjust its size to fit with lower part of the car. 9. Add Wheel colliders. In Hierarchy window, under Car node, delete front two wheels and right rear wheel. Just leave the left rear wheel. See figure below. Rename left rear wheel (Left_Rear) to Wheel. Add an empty game object and drag under the Car node. Rename it to WheelRL. Drag Wheel object under WheelRL. Then duplicate WheelRL three time. Rename them to WheelFL, WheelFR, WheelRR and move to them to corresponding place such as WheelFL to front left. See figure below.

5 Rotate Wheel objects under WheelFR, WheelRR by 180 degree. See figure below Add an empty game object and drag under the Car node. Rename it to WheelTransforms. Drag Wheel objects (WheelFL, WheelFR, WheelRL andwheelrr) under WheelTransforms. Add an empty game object and drag under the Car node. Rename it to WheelColliders. Copy Wheel objects (WheelFL, WheelFR, WheelRL andwheelrr) to WheelColliders. Delete all child objects of Wheel objects (WheelFL, WheelFR, WheelRL andwheelrr).

6 Add Wheelcollider component for WheelObjects under Wheelcolliders node. Adjust radius of Wheel Collider to fit with the wheels. Click the play icon, you will notice now the car stands on the terrain and does not fall through it. 10. In Hierarchy window, select Car object. Inspector window, click Add component. Add a C# script. Rename it as CarControlScript. Double click on script and open it in MonoDevelop. Add WheelCollider variables to the script. Save the script. using UnityEngine; using System.Collections; public class CarControlScript : MonoBehaviour { public WheelCollider WheelFL; public WheelCollider WheelFR; public WheelCollider WheelRL; public WheelCollider WheelRR; // Use this for initialization void Start () { // Update is called once per frame void Update () { 11. In Hierarchy window, select Car object. Inspector window, under Car Control Script, you will see four public variables. Drag corresponding collider objects from Hierarchy to the public variables. Results are shown in following figure.

7 12. In CarControlScript, Please replace Update() function with FixUpdate() function. Add following keyboard controlling codes to FixUpdate() function. void FixedUpdate () { WheelRR.motorTorque = maxtorque * Input.GetAxis("Vertical"); WheelRL.motorTorque = maxtorque * Input.GetAxis("Vertical"); WheelFL.steerAngle = 10 * Input.GetAxis("Horizontal"); WheelFR.steerAngle = 10 * Input.GetAxis("Horizontal"); Also Add a private variable to the class private float maxtorque = 50; motortorque controls Car speed. steerangle controls car direction. maxtorque controls the maximum speed of the car. FixUpdate() gets called every constant amount of time (hence "fixed"). FixedUpdate should be used instead of Update when dealing with Rigidbody. For example when adding a force to a rigidbody, you have to apply the force every fixed frame inside FixedUpdate instead of every frame inside Update. Now, test it out. You will find that car is very light and easy to flip over. That is because the center of mass is too high. 13. In CarControlScript, Add follow line of code to the Start() function. rigidbody.centerofmass = new Vector3(0,0,0); Now, you can test it out again. Controls should work fine. Save your Scene and save project. Car Camera control script 14. In Hierarchy window, select Main Camera. Inspector window, click Add component. Add a C# script. Rename it as CarCameraScript. Add following four public variables to CarCameraScript.

8 public Transform car; public float distance = 6.4f; public float height = 1.4f; public float rotationdamping = 3.0f; public float heightdamping = 2.0f; public float zoomratio = 0.5f; private Vector3 rotationvector; 14. In CarCameraScript, replace Update() function with LateUpdate() function. Add following codes. // void LateUpdate () { float wantedangle = car.eulerangles.y; float wantedheight = car.position.y + height; float myangle = transform.eulerangles.y; float myheight = transform.position.y; myangle = Mathf.LerpAngle(myAngle,wantedAngle,rotationDamping*Time.deltaTime); myheight = Mathf.Lerp (myheight,wantedheight,heightdamping*time.deltatime); Quaternion currentrotation = Quaternion.Euler(0,myAngle,0); transform.position = car.position; transform.position -= currentrotation*vector3.forward*distance; Vector3 newposition = transform.position; newposition.y = myheight; transform.position = newposition; transform.lookat(car); LateUpdate() is called every frame, if the Behaviour is enabled. LateUpdate is called after all Update functions have been called. This is useful to order script execution. For example a follow camera should always be implemented in LateUpdate because it tracks objects that might have moved inside Update. Both Mathf.LerpAngle and Mathf.Lerp are used to create smooth movement of camera. 15. In Hierarchy window, drag Car object (Do not select it) to CarCamerScript s Car object. Save your Scene and save project.