Box2D  2.3.0
A 2D Physics Engine for Games
b2Rope.h
1 /*
2 * Copyright (c) 2011 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 B2_ROPE_H
20 #define B2_ROPE_H
21 
22 #include <Box2D/Common/b2Math.h>
23 
24 class b2Draw;
25 
27 struct b2RopeDef
28 {
29  b2RopeDef()
30  {
31  vertices = NULL;
32  count = 0;
33  masses = NULL;
34  gravity.SetZero();
35  damping = 0.1f;
36  k2 = 0.9f;
37  k3 = 0.1f;
38  }
39 
41  b2Vec2* vertices;
42 
44  int32 count;
45 
47  float32* masses;
48 
50  b2Vec2 gravity;
51 
53  float32 damping;
54 
56  float32 k2;
57 
59  float32 k3;
60 };
61 
63 class b2Rope
64 {
65 public:
66  b2Rope();
67  ~b2Rope();
68 
70  void Initialize(const b2RopeDef* def);
71 
73  void Step(float32 timeStep, int32 iterations);
74 
76  int32 GetVertexCount() const
77  {
78  return m_count;
79  }
80 
82  const b2Vec2* GetVertices() const
83  {
84  return m_ps;
85  }
86 
88  void Draw(b2Draw* draw) const;
89 
91  void SetAngle(float32 angle);
92 
93 private:
94 
95  void SolveC2();
96  void SolveC3();
97 
98  int32 m_count;
99  b2Vec2* m_ps;
100  b2Vec2* m_p0s;
101  b2Vec2* m_vs;
102 
103  float32* m_ims;
104 
105  float32* m_Ls;
106  float32* m_as;
107 
108  b2Vec2 m_gravity;
109  float32 m_damping;
110 
111  float32 m_k2;
112  float32 m_k3;
113 };
114 
115 #endif
float32 k2
Stretching stiffness.
Definition: b2Rope.h:56
void SetZero()
Set this vector to all zeros.
Definition: b2Math.h:62
Definition: b2Draw.h:35
A 2D column vector.
Definition: b2Math.h:53
Definition: b2Rope.h:63
Definition: b2Rope.h:27
float32 k3
Bending stiffness. Values above 0.5 can make the simulation blow up.
Definition: b2Rope.h:59