120 lines
3.5 KiB
C++
120 lines
3.5 KiB
C++
/*
|
|
* Copyright (c) 2006-2009 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"
|
|
#include "../b2Fixture.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;
|
|
}
|
|
|
|
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(b2Fixture* shape=body->GetFixtureList();shape;shape=shape->GetNext())
|
|
{
|
|
b2Vec2 sc(0,0);
|
|
float32 sarea = shape->ComputeSubmergedArea(normal, offset, &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) const
|
|
{
|
|
void* mem = allocator->Allocate(sizeof(b2BuoyancyController));
|
|
return new (mem) b2BuoyancyController(this);
|
|
}
|