1 /*
2 * Copyright (c) 2008-2009 Erin Catto http://www.box2d.org
3 *
4 * This software is provided 'as-is', without any express or implied
5 * warranty.  In no event will the authors be held liable for any damages
6 * arising from the use of this software.
7 * Permission is granted to anyone to use this software for any purpose,
8 * including commercial applications, and to alter it and redistribute it
9 * freely, subject to the following restrictions:
10 * 1. The origin of this software must not be misrepresented; you must not
11 * claim that you wrote the original software. If you use this software
12 * in a product, an acknowledgment in the product documentation would be
13 * appreciated but is not required.
14 * 2. Altered source versions must be plainly marked as such, and must not be
15 * misrepresented as being the original software.
16 * 3. This notice may not be removed or altered from any source distribution.
17 */
18 
19 #ifndef BREAKABLE_TEST_H
20 #define BREAKABLE_TEST_H
21 
22 // This is used to test sensor shapes.
23 class Breakable : public Test
24 {
25 public:
26 
27     enum
28     {
29         e_count = 7
30     };
31 
Breakable()32     Breakable()
33     {
34         // Ground body
35         {
36             b2BodyDef bd;
37             b2Body* ground = m_world->CreateBody(&bd);
38 
39             b2EdgeShape shape;
40             shape.Set(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
41             ground->CreateFixture(&shape, 0.0f);
42         }
43 
44         // Breakable dynamic body
45         {
46             b2BodyDef bd;
47             bd.type = b2_dynamicBody;
48             bd.position.Set(0.0f, 40.0f);
49             bd.angle = 0.25f * b2_pi;
50             m_body1 = m_world->CreateBody(&bd);
51 
52             m_shape1.SetAsBox(0.5f, 0.5f, b2Vec2(-0.5f, 0.0f), 0.0f);
53             m_piece1 = m_body1->CreateFixture(&m_shape1, 1.0f);
54 
55             m_shape2.SetAsBox(0.5f, 0.5f, b2Vec2(0.5f, 0.0f), 0.0f);
56             m_piece2 = m_body1->CreateFixture(&m_shape2, 1.0f);
57         }
58 
59         m_break = false;
60         m_broke = false;
61     }
62 
PostSolve(b2Contact * contact,const b2ContactImpulse * impulse)63     void PostSolve(b2Contact* contact, const b2ContactImpulse* impulse)
64     {
65         if (m_broke)
66         {
67             // The body already broke.
68             return;
69         }
70 
71         // Should the body break?
72         int32 count = contact->GetManifold()->pointCount;
73 
74         float32 maxImpulse = 0.0f;
75         for (int32 i = 0; i < count; ++i)
76         {
77             maxImpulse = b2Max(maxImpulse, impulse->normalImpulses[i]);
78         }
79 
80         if (maxImpulse > 40.0f)
81         {
82             // Flag the body for breaking.
83             m_break = true;
84         }
85     }
86 
Break()87     void Break()
88     {
89         // Create two bodies from one.
90         b2Body* body1 = m_piece1->GetBody();
91         b2Vec2 center = body1->GetWorldCenter();
92 
93         body1->DestroyFixture(m_piece2);
94         m_piece2 = NULL;
95 
96         b2BodyDef bd;
97         bd.type = b2_dynamicBody;
98         bd.position = body1->GetPosition();
99         bd.angle = body1->GetAngle();
100 
101         b2Body* body2 = m_world->CreateBody(&bd);
102         m_piece2 = body2->CreateFixture(&m_shape2, 1.0f);
103 
104         // Compute consistent velocities for new bodies based on
105         // cached velocity.
106         b2Vec2 center1 = body1->GetWorldCenter();
107         b2Vec2 center2 = body2->GetWorldCenter();
108 
109         b2Vec2 velocity1 = m_velocity + b2Cross(m_angularVelocity, center1 - center);
110         b2Vec2 velocity2 = m_velocity + b2Cross(m_angularVelocity, center2 - center);
111 
112         body1->SetAngularVelocity(m_angularVelocity);
113         body1->SetLinearVelocity(velocity1);
114 
115         body2->SetAngularVelocity(m_angularVelocity);
116         body2->SetLinearVelocity(velocity2);
117     }
118 
Step(Settings * settings)119     void Step(Settings* settings)
120     {
121         if (m_break)
122         {
123             Break();
124             m_broke = true;
125             m_break = false;
126         }
127 
128         // Cache velocities to improve movement on breakage.
129         if (m_broke == false)
130         {
131             m_velocity = m_body1->GetLinearVelocity();
132             m_angularVelocity = m_body1->GetAngularVelocity();
133         }
134 
135         Test::Step(settings);
136     }
137 
Create()138     static Test* Create()
139     {
140         return new Breakable;
141     }
142 
143     b2Body* m_body1;
144     b2Vec2 m_velocity;
145     float32 m_angularVelocity;
146     b2PolygonShape m_shape1;
147     b2PolygonShape m_shape2;
148     b2Fixture* m_piece1;
149     b2Fixture* m_piece2;
150 
151     bool m_broke;
152     bool m_break;
153 };
154 
155 #endif
156