TopDown Car demo
作者：互联网
1 //这个是老外教程附带的文件，直接复制下来放到Testbed例子的目录。你懂得
2 /* * Author: Chris Campbell - www.iforce2d.net * * Copyright (c) 2006-2011 Erin Catto http://www.box2d.org *
3 * This software is provided 'as-is', without any express or implied * warranty. In no event will the authors be held liable for any damages * arising from the use of this software.
4 * Permission is granted to anyone to use this software for any purpose, * including commercial applications, and to alter it and redistribute it * freely, subject to the following restrictions:
5 * 1. The origin of this software must not be misrepresented; you must not * claim that you wrote the original software. If you use this software * in a product, an acknowledgment in the product documentation would be * appreciated but is not required.
6 * 2. Altered source versions must be plainly marked as such, and must not be * misrepresented as being the original software.
7 * 3. This notice may not be removed or altered from any source distribution. */
8 #ifndef IFORCE2D_TOPDOWN_CAR_H
9 #define IFORCE2D_TOPDOWN_CAR_H
10 #include #include
11 #ifndef DEGTORAD
12 #define DEGTORAD 0.0174532925199432957f
13 #define RADTODEG 57.295779513082320876f
14 #endif
15 enum {
16 TDC_LEFT = 0x1,
17 TDC_RIGHT = 0x2,
18 TDC_UP = 0x4,
19 TDC_DOWN = 0x8
20 }; //types of fixture user data
21 enum fixtureUserDataType
22 {
23 FUD_CAR_TIRE,
24 FUD_GROUND_AREA
25 }; //a class to allow subclassing of different fixture user data
26 class FixtureUserData {
27 fixtureUserDataType m_type;
28 protected:
29 FixtureUserData(fixtureUserDataType type) : m_type(type) {}
30 public:
31 virtual fixtureUserDataType getType() {
32 return m_type;
33 }
34 virtual ~FixtureUserData()
35 {
36 }
37 }; //class to allow marking a fixture as a car tire
38 class CarTireFUD : public FixtureUserData
39 {
40 public:
41 CarTireFUD() : FixtureUserData(FUD_CAR_TIRE) {}
42 };
43 //class to allow marking a fixture as a ground area
44 class GroundAreaFUD : public FixtureUserData {
45 public:
46 float frictionModifier;
47 bool outOfCourse;
48 GroundAreaFUD(float fm, bool ooc) : FixtureUserData(FUD_GROUND_AREA)
49 {
50 frictionModifier = fm; outOfCourse = ooc;
51 }
52 };
53 class TDTire
54 {
55 public:
56 b2Body* m_body;
57 float m_maxForwardSpeed;
58 float m_maxBackwardSpeed;
59 float m_maxDriveForce;
60 float m_maxLateralImpulse;
61 std::set m_groundAreas;
62 float m_currentTraction;
63 TDTire(b2World* world) {
64 b2BodyDef bodyDef;
65 bodyDef.type = b2_dynamicBody;
66 m_body = world->CreateBody(&bodyDef);
67 b2PolygonShape polygonShape;
68 polygonShape.SetAsBox(0.5f, 1.25f);
69 b2Fixture* fixture = m_body->CreateFixture(&polygonShape, 1);//shape, density
70 fixture->SetUserData(new CarTireFUD());
71 m_body->SetUserData(this);
72 m_currentTraction = 1;
73 }
74 ~TDTire() { m_body->GetWorld()->DestroyBody(m_body); }
75 void setCharacteristics(float maxForwardSpeed, float maxBackwardSpeed, float maxDriveForce, float maxLateralImpulse)
76 {
77 m_maxForwardSpeed = maxForwardSpeed; m_maxBackwardSpeed = maxBackwardSpeed; m_maxDriveForce = maxDriveForce;
78 m_maxLateralImpulse = maxLateralImpulse;
79 }
80 void addGroundArea(GroundAreaFUD* ga) {
81 m_groundAreas.insert(ga);
82 updateTraction();
83 } void removeGroundArea(GroundAreaFUD* ga) { m_groundAreas.erase(ga); updateTraction(); }
84 void updateTraction() {
85 if (m_groundAreas.empty()) m_currentTraction = 1; else { //find area with highest traction
86 m_currentTraction = 0; std::set::iterator it = m_groundAreas.begin();
87 while (it != m_groundAreas.end()) { GroundAreaFUD* ga = *it; if (ga->frictionModifier > m_currentTraction) m_currentTraction = ga->frictionModifier; ++it; }
88 }
89 }
90 b2Vec2 getLateralVelocity() {
91 b2Vec2 currentRightNormal = m_body->GetWorldVector(b2Vec2(1, 0));
92 return b2Dot(currentRightNormal, m_body->GetLinearVelocity()) * currentRightNormal;
93 }
94 b2Vec2 getForwardVelocity() {
95 b2Vec2 currentForwardNormal = m_body->GetWorldVector(b2Vec2(0, 1));
96 return b2Dot(currentForwardNormal, m_body->GetLinearVelocity()) * currentForwardNormal;
97 }
98 void updateFriction() { //lateral linear velocity
99 b2Vec2 impulse = m_body->GetMass() * -getLateralVelocity();
100 if (impulse.Length() > m_maxLateralImpulse)
101 impulse *= m_maxLateralImpulse / impulse.Length();
102 m_body->ApplyLinearImpulse(m_currentTraction * impulse, m_body->GetWorldCenter()); //angular velocity
103 m_body->ApplyAngularImpulse(m_currentTraction * 0.1f * m_body->GetInertia() * -m_body->GetAngularVelocity()); //forward linear velocity
104 b2Vec2 currentForwardNormal = getForwardVelocity();
105 float currentForwardSpeed = currentForwardNormal.Normalize();
106 float dragForceMagnitude = -2 * currentForwardSpeed;
107 m_body->ApplyForce(m_currentTraction * dragForceMagnitude * currentForwardNormal, m_body->GetWorldCenter());
108 }
109 void updateDrive(int controlState) { //find desired speed
110 float desiredSpeed = 0;
111 switch (controlState & (TDC_UP | TDC_DOWN))
112 {
113 case TDC_UP: desiredSpeed = m_maxForwardSpeed; break;
114 case TDC_DOWN: desiredSpeed = m_maxBackwardSpeed; break;
115 default: return;//do nothing } //find current speed in forward direction
116 b2Vec2 currentForwardNormal = m_body->GetWorldVector(b2Vec2(0, 1));
117 float currentSpeed = b2Dot(getForwardVelocity(), currentForwardNormal); //apply necessary force
118 float force = 0;
119 if (desiredSpeed > currentSpeed)
120 force = m_maxDriveForce;
121 else if (desiredSpeed < currentSpeed)
122 force = -m_maxDriveForce; else return;
123 m_body->ApplyForce(m_currentTraction * force * currentForwardNormal, m_body->GetWorldCenter());
124 }
125 void updateTurn(int controlState) {
126 float desiredTorque = 0;
127 switch (controlState & (TDC_LEFT | TDC_RIGHT))
128 {
129 case TDC_LEFT:
130 desiredTorque = 15;
131 break;
132 case TDC_RIGHT:
133 desiredTorque = -15;
134 break;
135 default:;//nothing
136 }
137 m_body->ApplyTorque(desiredTorque);
138 }
139 };
140 }
141 class TDCar {
142 b2Body* m_body;
143 std::vector m_tires;
144 b2RevoluteJoint* flJoint, * frJoint;
145 public:
146 TDCar(b2World* world)
147 {
148 //create car body
149 b2BodyDef bodyDef;
150 bodyDef.type = b2_dynamicBody; m_body = world->CreateBody(&bodyDef);
151 m_body->SetAngularDamping(3); b2Vec2 vertices[8]; vertices[0].Set(1.5, 0);
152 vertices[1].Set(3, 2.5); vertices[2].Set(2.8, 5.5); vertices[3].Set(1, 10);
153 vertices[4].Set(-1, 10); vertices[5].Set(-2.8, 5.5); vertices[6].Set(-3, 2.5);
154 vertices[7].Set(-1.5, 0); b2PolygonShape polygonShape; polygonShape.Set(vertices, 8);
155 b2Fixture* fixture = m_body->CreateFixture(&polygonShape, 0.1f);//shape, density //prepare common joint parameters
156 b2RevoluteJointDef jointDef;
157 jointDef.bodyA = m_body;
158 jointDef.enableLimit = true;
159 jointDef.lowerAngle = 0;
160 jointDef.upperAngle = 0;
161 jointDef.localAnchorB.SetZero();//center of tire float maxForwardSpeed = 250; float maxBackwardSpeed = -40; float backTireMaxDriveForce = 300; float frontTireMaxDriveForce = 500; float backTireMaxLateralImpulse = 8.5; float frontTireMaxLateralImpulse = 7.5; //back left tire TDTire* tire = new TDTire(world); tire->setCharacteristics(maxForwardSpeed, maxBackwardSpeed, backTireMaxDriveForce, backTireMaxLateralImpulse); jointDef.bodyB = tire->m_body; jointDef.localAnchorA.Set( -3, 0.75f ); world->CreateJoint( &jointDef ); m_tires.push_back(tire); //back right tire tire = new TDTire(world); tire->setCharacteristics(maxForwardSpeed, maxBackwardSpeed, backTireMaxDriveForce, backTireMaxLateralImpulse); jointDef.bodyB = tire->m_body; jointDef.localAnchorA.Set( 3, 0.75f ); world->CreateJoint( &jointDef ); m_tires.push_back(tire); //front left tire tire = new TDTire(world); tire->setCharacteristics(maxForwardSpeed, maxBackwardSpeed, frontTireMaxDriveForce, frontTireMaxLateralImpulse); jointDef.bodyB = tire->m_body; jointDef.localAnchorA.Set( -3, 8.5f ); flJoint = (b2RevoluteJoint*)world->CreateJoint( &jointDef ); m_tires.push_back(tire); //front right tire tire = new TDTire(world); tire->setCharacteristics(maxForwardSpeed, maxBackwardSpeed, frontTireMaxDriveForce, frontTireMaxLateralImpulse); jointDef.bodyB = tire->m_body; jointDef.localAnchorA.Set( 3, 8.5f ); frJoint = (b2RevoluteJoint*)world->CreateJoint( &jointDef ); m_tires.push_back(tire); } ~TDCar() { for (int i = 0; i < m_tires.size(); i++) delete m_tires[i]; } void update(int controlState) { for (int i = 0; i < m_tires.size(); i++) m_tires[i]->updateFriction();
162 for (int i = 0; i < m_tires.size(); i++)
163 m_tires[i]->updateDrive(controlState); //control steering
164 float lockAngle = 35 * DEGTORAD;
165 float turnSpeedPerSec = 160 * DEGTORAD;//from lock to lock in 0.5 sec
166 float turnPerTimeStep = turnSpeedPerSec / 60.0f;
167 float desiredAngle = 0;
168 switch (controlState & (TDC_LEFT | TDC_RIGHT))
169 {
170 case TDC_LEFT:
171 desiredAngle = lockAngle;
172 break;
173 case TDC_RIGHT:
174 desiredAngle = -lockAngle;
175 break;
176 default:;//nothing
177 }
178 float angleNow = flJoint->GetJointAngle();
179 float angleToTurn = desiredAngle - angleNow;
180 angleToTurn = b2Clamp(angleToTurn, -turnPerTimeStep, turnPerTimeStep);
181 float newAngle = angleNow + angleToTurn;
182 flJoint->SetLimits(newAngle, newAngle);
183 frJoint->SetLimits(newAngle, newAngle);
184 }
185 };
186 class MyDestructionListener : public b2DestructionListener {
187 void SayGoodbye(b2Fixture* fixture) {
188 if (FixtureUserData* fud = (FixtureUserData*)fixture->GetUserData())
189 delete fud;
190 } //(unused but must implement all pure virtual functions)
191 void SayGoodbye(b2Joint* joint) {}
192 };
193 class iforce2d_TopdownCar : public Test {
194 public:
195 iforce2d_TopdownCar()
196 {
197 m_world->SetGravity(b2Vec2(0, 0));
198 m_world->SetDestructionListener(&m_destructionListener); //set up ground areas
199 {
200 b2BodyDef bodyDef; m_groundBody = m_world->CreateBody(&bodyDef);
201 b2PolygonShape polygonShape; b2FixtureDef fixtureDef;
202 fixtureDef.shape = &polygonShape; fixtureDef.isSensor = true;
203 polygonShape.SetAsBox(9, 7, b2Vec2(-10, 15), 20 * DEGTORAD);
204 b2Fixture* groundAreaFixture = m_groundBody->CreateFixture(&fixtureDef);
205 groundAreaFixture->SetUserData(new GroundAreaFUD(0.5f, false));
206 polygonShape.SetAsBox(9, 5, b2Vec2(5, 20), -40 * DEGTORAD);
207 groundAreaFixture = m_groundBody->CreateFixture(&fixtureDef);
208 groundAreaFixture->SetUserData(new GroundAreaFUD(0.2f, false));
209 } //
210 m_tire = new TDTire(m_world); //
211 m_tire->setCharacteristics(100, -20, 150);
212 m_car = new TDCar(m_world);
213 m_controlState = 0;
214 }
215
216 ~iforce2d_TopdownCar() { //
217 delete m_tire; delete m_car; m_world->DestroyBody(m_groundBody);
218 }
219 void Keyboard(unsigned char key) {
220 switch (key) {
221 case 'a': m_controlState |= TDC_LEFT; break;
222 case 'd': m_controlState |= TDC_RIGHT; break;
223 case 'w': m_controlState |= TDC_UP; break;
224 case 's': m_controlState |= TDC_DOWN; break;
225 default: Test::Keyboard(key);
226 }
227 }
228 void KeyboardUp(unsigned char key)
229 {
230 switch (key) {
231 case 'a':
232 m_controlState &= ~TDC_LEFT; break;
233 case 'd':
234 m_controlState &= ~TDC_RIGHT;
235 break;
236 case 'w':
237 m_controlState &= ~TDC_UP;
238 break;
239 case 's':
240 m_controlState &= ~TDC_DOWN;
241 break;
242 default:
243 Test::Keyboard(key);
244 }
245 }
246 void handleContact(b2Contact* contact, bool began)
247 {
248 b2Fixture* a = contact->GetFixtureA();
249 b2Fixture* b = contact->GetFixtureB();
250 FixtureUserData* fudA = (FixtureUserData*)a->GetUserData();
251 FixtureUserData* fudB = (FixtureUserData*)b->GetUserData();
252 if (!fudA || !fudB)
253 return;
254 if (fudA->getType() == FUD_CAR_TIRE || fudB->getType() == FUD_GROUND_AREA)
255 tire_vs_groundArea(a, b, began);
256 else if (fudA->getType() == FUD_GROUND_AREA || fudB->getType() == FUD_CAR_TIRE)
257 tire_vs_groundArea(b, a, began);
258 }
259 void BeginContact(b2Contact* contact)
260 {
261 handleContact(contact, true);
262 }
263 void EndContact(b2Contact* contact)
264 {
265 handleContact(contact, false);
266 }
267 void tire_vs_groundArea(b2Fixture* tireFixture, b2Fixture* groundAreaFixture, bool began)
268 {
269 TDTire* tire = (TDTire*)tireFixture->GetBody()->GetUserData();
270 GroundAreaFUD* gaFud = (GroundAreaFUD*)groundAreaFixture->GetUserData();
271 if (began) tire->addGroundArea(gaFud); else tire->removeGroundArea(gaFud);
272 }
273 void Step(Settings* settings) {
274 /*m_tire->updateFriction();
275 m_tire->updateDrive(m_controlState);
276 m_tire->updateTurn(m_controlState);*/
277 m_car->update(m_controlState); Test::Step(settings); //show some useful info
278 m_debugDraw.DrawString(5, m_textLine, "Press w/a/s/d to control the car");
279 m_textLine += 15; //
280 m_debugDraw.DrawString(5, m_textLine, "Tire traction: %.2f", m_tire->m_currentTraction); //
281 m_textLine += 15;
282 }
283 static Test* Create()
284 {
285 return new iforce2d_TopdownCar;
286 }
287 int m_controlState;
288 MyDestructionListener m_destructionListener;
289 b2Body* m_groundBody; //
290 TDTire* m_tire;
291 TDCar* m_car;
292 };
293 #endif
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标签：body,tire,TDC,Car,TopDown,float,controlState,demo,world 来源： https://www.cnblogs.com/yang131/p/14372236.html