void RigidBody2D::CopyBodyData(cpBody* body)
{
cpBodySetAngle(m_handle, cpBodyGetAngle(body));
cpBodySetAngularVelocity(m_handle, cpBodyGetAngularVelocity(body));
cpBodySetCenterOfGravity(m_handle, cpBodyGetCenterOfGravity(body));
cpBodySetForce(m_handle, cpBodyGetForce(body));
cpBodySetPosition(m_handle, cpBodyGetPosition(body));
cpBodySetTorque(m_handle, cpBodyGetTorque(body));
cpBodySetVelocity(m_handle, cpBodyGetVelocity(body));
}
void RigidBody2D::CopyBodyData(cpBody* from, cpBody* to)
{
cpBodySetAngle(to, cpBodyGetAngle(from));
cpBodySetAngularVelocity(to, cpBodyGetAngularVelocity(from));
cpBodySetCenterOfGravity(to, cpBodyGetCenterOfGravity(from));
cpBodySetForce(to, cpBodyGetForce(from));
cpBodySetPosition(to, cpBodyGetPosition(from));
cpBodySetTorque(to, cpBodyGetTorque(from));
cpBodySetVelocity(to, cpBodyGetVelocity(from));
}
static int l_physics_getBodyCenterOfGravity(lua_State* state)
{
l_tools_checkUserDataPlusErrMsg(state, 1, "You must provide a body");
l_physics_Body* body = (l_physics_Body*)lua_touserdata(state, 1);
cpVect vec = cpBodyGetCenterOfGravity(body->body);
lua_pushnumber(state, vec.x);
lua_pushnumber(state, vec.y);
return 2;
}
Vector2f RigidBody2D::GetCenterOfGravity(CoordSys coordSys) const
{
cpVect cog = cpBodyGetCenterOfGravity(m_handle);
switch (coordSys)
{
case CoordSys_Global:
cog = cpBodyLocalToWorld(m_handle, cog);
break;
case CoordSys_Local:
break; // Nothing to do
}
return Vector2f(static_cast<float>(cog.x), static_cast<float>(cog.y));
}
cpBool Buoyancy::WaterPreSolve(cpArbiter *arb, cpSpace *space, void *ptr)
{
CP_ARBITER_GET_SHAPES(arb, water, poly);
cpBody *body = cpShapeGetBody(poly);
// Get the top of the water sensor bounding box to use as the water level.
cpFloat level = cpShapeGetBB(water).t;
// Clip the polygon against the water level
int count = cpPolyShapeGetCount(poly);
int clippedCount = 0;
#ifdef _MSC_VER
// MSVC is pretty much the only compiler in existence that doesn't support variable sized arrays.
cpVect clipped[10];
#else
cpVect clipped[count + 1];
#endif
for(int i=0, j=count-1; i<count; j=i, i++){
cpVect a = cpBodyLocalToWorld(body, cpPolyShapeGetVert(poly, j));
cpVect b = cpBodyLocalToWorld(body, cpPolyShapeGetVert(poly, i));
if(a.y < level){
clipped[clippedCount] = a;
clippedCount++;
}
cpFloat a_level = a.y - level;
cpFloat b_level = b.y - level;
if(a_level*b_level < 0.0f){
cpFloat t = cpfabs(a_level)/(cpfabs(a_level) + cpfabs(b_level));
clipped[clippedCount] = cpvlerp(a, b, t);
clippedCount++;
}
}
// Calculate buoyancy from the clipped polygon area
cpFloat clippedArea = cpAreaForPoly(clippedCount, clipped, 0.0f);
cpFloat displacedMass = clippedArea*FLUID_DENSITY;
cpVect centroid = cpCentroidForPoly(clippedCount, clipped);
cpDataPointer data = ptr;
DrawPolygon(clippedCount, clipped, 0.0f, RGBAColor(0, 0, 1, 1), RGBAColor(0, 0, 1, 0.1f), data);
DrawDot(5, centroid, RGBAColor(0, 0, 1, 1), data);
cpFloat dt = cpSpaceGetCurrentTimeStep(space);
cpVect g = cpSpaceGetGravity(space);
// Apply the buoyancy force as an impulse.
cpBodyApplyImpulseAtWorldPoint(body, cpvmult(g, -displacedMass*dt), centroid);
// Apply linear damping for the fluid drag.
cpVect v_centroid = cpBodyGetVelocityAtWorldPoint(body, centroid);
cpFloat k = k_scalar_body(body, centroid, cpvnormalize(v_centroid));
cpFloat damping = clippedArea*FLUID_DRAG*FLUID_DENSITY;
cpFloat v_coef = cpfexp(-damping*dt*k); // linear drag
// cpFloat v_coef = 1.0/(1.0 + damping*dt*cpvlength(v_centroid)*k); // quadratic drag
cpBodyApplyImpulseAtWorldPoint(body, cpvmult(cpvsub(cpvmult(v_centroid, v_coef), v_centroid), 1.0/k), centroid);
// Apply angular damping for the fluid drag.
cpVect cog = cpBodyLocalToWorld(body, cpBodyGetCenterOfGravity(body));
cpFloat w_damping = cpMomentForPoly(FLUID_DRAG*FLUID_DENSITY*clippedArea, clippedCount, clipped, cpvneg(cog), 0.0f);
cpBodySetAngularVelocity(body, cpBodyGetAngularVelocity(body)*cpfexp(-w_damping*dt/cpBodyGetMoment(body)));
return cpTrue;
}
void RCPBody::applyImpulse(RVector const & impulse)
{
if (mBody) {
cpBodyApplyImpulseAtWorldPoint(mBody, cpv(impulse.x(), impulse.y()), cpBodyLocalToWorld(mBody, cpBodyGetCenterOfGravity(mBody)));
}
}
