1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
|
/*
* Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com
*
* 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.
* 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:
* 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.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/
#include "b2BuoyancyController.h"
b2BuoyancyController::b2BuoyancyController(const b2BuoyancyControllerDef* def) : b2Controller(def)
{
normal = def->normal;
offset = def->offset;
density = def->density;
velocity = def->velocity;
linearDrag = def->linearDrag;
angularDrag = def->angularDrag;
useDensity = def->useDensity;
useWorldGravity = def->useWorldGravity;
gravity = def->gravity;
m_type = e_buoyancyController;
}
void b2BuoyancyController::Step(const b2TimeStep& step)
{
B2_NOT_USED(step);
if(!m_bodyList)
return;
if(useWorldGravity){
gravity = m_world->GetGravity();
}
for(b2ControllerEdge *i=m_bodyList;i;i=i->nextBody){
b2Body* body = i->body;
if(body->IsSleeping()){
//Buoyancy force is just a function of position,
//so unlike most forces, it is safe to ignore sleeping bodes
continue;
}
b2Vec2 areac(0,0);
b2Vec2 massc(0,0);
float32 area = 0;
float32 mass = 0;
for(b2Shape* shape=body->GetShapeList();shape;shape=shape->GetNext()){
b2Vec2 sc(0,0);
float32 sarea = shape->ComputeSubmergedArea(normal,offset,body->GetXForm(),&sc);
area += sarea;
areac.x += sarea * sc.x;
areac.y += sarea * sc.y;
float shapeDensity = 0;
if(useDensity){
//TODO: Expose density publicly
shapeDensity=shape->GetDensity();
}else{
shapeDensity = 1;
}
mass += sarea*shapeDensity;
massc.x += sarea * sc.x * shapeDensity;
massc.y += sarea * sc.y * shapeDensity;
}
areac.x/=area;
areac.y/=area;
b2Vec2 localCentroid = b2MulT(body->GetXForm(),areac);
massc.x/=mass;
massc.y/=mass;
if(area<B2_FLT_EPSILON)
continue;
//Buoyancy
b2Vec2 buoyancyForce = -density*area*gravity;
body->ApplyForce(buoyancyForce,massc);
//Linear drag
b2Vec2 dragForce = body->GetLinearVelocityFromWorldPoint(areac) - velocity;
dragForce *= -linearDrag*area;
body->ApplyForce(dragForce,areac);
//Angular drag
//TODO: Something that makes more physical sense?
body->ApplyTorque(-body->GetInertia()/body->GetMass()*area*body->GetAngularVelocity()*angularDrag);
}
}
void b2BuoyancyController::Draw(b2DebugDraw *debugDraw)
{
float32 r = 1000;
b2Vec2 p1 = offset * normal + b2Cross(normal, r);
b2Vec2 p2 = offset * normal - b2Cross(normal, r);
b2Color color(0,0,0.8f);
debugDraw->DrawSegment(p1, p2, color);
}
void b2BuoyancyController::Destroy(b2BlockAllocator* allocator)
{
allocator->Free(this, sizeof(b2BuoyancyController));
}
b2BuoyancyController* b2BuoyancyControllerDef::Create(b2BlockAllocator* allocator)
{
void* mem = allocator->Allocate(sizeof(b2BuoyancyController));
return new (mem) b2BuoyancyController(this);
}
|
