void PhysicsShapePolygon::updateScale()
{
cpFloat factorX = _newScaleX / _scaleX;
cpFloat factorY = _newScaleY / _scaleY;
auto shape = _cpShapes.front();
int count = cpPolyShapeGetCount(shape);
cpVect* vects = new cpVect[count];
for(int i=0;i<count;++i)
vects[i] = cpPolyShapeGetVert(shape, i);
for (int i = 0; i < count; ++i)
{
vects[i].x *= factorX;
vects[i].y *= factorY;
}
// convert hole to clockwise
if (factorX * factorY < 0)
{
for (int i = 0; i < count / 2; ++i)
{
cpVect v = vects[i];
vects[i] = vects[count - i - 1];
vects[count - i - 1] = v;
}
}
cpPolyShapeSetVertsRaw(shape, count, vects);
CC_SAFE_DELETE_ARRAY(vects);
PhysicsShape::updateScale();
}
void PhysicsShapePolygon::getPoints(Vec2* outPoints) const
{
auto shape = _cpShapes.front();
int count = cpPolyShapeGetCount(shape);
cpVect* vecs = new cpVect[count];
for(int i=0;i<count;++i)
vecs[i] = cpPolyShapeGetVert(shape, i);
PhysicsHelper::cpvs2points(vecs, outPoints, count);
CC_SAFE_DELETE_ARRAY(vecs);
}
cpVect
cpPolyShapeGetVert(const cpShape *shape, int i)
{
cpAssertHard(shape->klass == &polyClass, "Shape is not a poly shape.");
int count = cpPolyShapeGetCount(shape);
cpAssertHard(0 <= i && i < count, "Index out of range.");
return ((cpPolyShape *)shape)->planes[i + count].v0;
}
float PhysicsShapePolygon::calculateArea()
{
auto shape = _cpShapes.front();
int count = cpPolyShapeGetCount(shape);
cpVect* vecs = new cpVect[count];
for(int i=0;i<count;++i)
vecs[i] = cpPolyShapeGetVert(shape, i);
float area = PhysicsHelper::cpfloat2float(cpAreaForPoly(count, vecs, cpPolyShapeGetRadius(shape)));
CC_SAFE_DELETE_ARRAY(vecs);
return area;
}
Vec2 PhysicsShapePolygon::getCenter()
{
auto shape = _cpShapes.front();
int count = cpPolyShapeGetCount(shape);
cpVect* vecs = new cpVect[count];
for(int i=0;i<count;++i)
vecs[i] = cpPolyShapeGetVert(shape, i);
Vec2 center = PhysicsHelper::cpv2point(cpCentroidForPoly(count, vecs));
CC_SAFE_DELETE_ARRAY(vecs);
return center;
}
float PhysicsShapePolygon::calculateDefaultMoment()
{
if(_mass == PHYSICS_INFINITY)
{
return PHYSICS_INFINITY;
}
else
{
auto shape = _cpShapes.front();
int count = cpPolyShapeGetCount(shape);
cpVect* vecs = new cpVect[count];
for(int i=0;i<count;++i)
vecs[i] = cpPolyShapeGetVert(shape, i);
float moment = PhysicsHelper::cpfloat2float(cpMomentForPoly(_mass, count, vecs, cpvzero, cpPolyShapeGetRadius(shape)));
CC_SAFE_DELETE_ARRAY(vecs);
return moment;
}
}
void Slice::ClipPoly(cpSpace *space, cpShape *shape, cpVect n, cpFloat dist)
{
cpBody *body = cpShapeGetBody(shape);
int count = cpPolyShapeGetCount(shape);
int clippedCount = 0;
cpVect *clipped = (cpVect *)alloca((count + 1)*sizeof(cpVect));
for(int i=0, j=count-1; i<count; j=i, i++){
cpVect a = cpBodyLocalToWorld(body, cpPolyShapeGetVert(shape, j));
cpFloat a_dist = cpvdot(a, n) - dist;
if(a_dist < 0.0){
clipped[clippedCount] = a;
clippedCount++;
}
cpVect b = cpBodyLocalToWorld(body, cpPolyShapeGetVert(shape, i));
cpFloat b_dist = cpvdot(b, n) - dist;
if(a_dist*b_dist < 0.0f){
cpFloat t = cpfabs(a_dist)/(cpfabs(a_dist) + cpfabs(b_dist));
clipped[clippedCount] = cpvlerp(a, b, t);
clippedCount++;
}
}
cpVect centroid = cpCentroidForPoly(clippedCount, clipped);
cpFloat mass = cpAreaForPoly(clippedCount, clipped, 0.0f)*DENSITY;
cpFloat moment = cpMomentForPoly(mass, clippedCount, clipped, cpvneg(centroid), 0.0f);
cpBody *new_body = cpSpaceAddBody(space, cpBodyNew(mass, moment));
cpBodySetPosition(new_body, centroid);
cpBodySetVelocity(new_body, cpBodyGetVelocityAtWorldPoint(body, centroid));
cpBodySetAngularVelocity(new_body, cpBodyGetAngularVelocity(body));
cpTransform transform = cpTransformTranslate(cpvneg(centroid));
cpShape *new_shape = cpSpaceAddShape(space, cpPolyShapeNew(new_body, clippedCount, clipped, transform, 0.0));
// Copy whatever properties you have set on the original shape that are important
cpShapeSetFriction(new_shape, cpShapeGetFriction(shape));
}
int PhysicsShapePolygon::getPointsCount() const
{
return cpPolyShapeGetCount(_cpShapes.front());
}
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;
}
