public static void createBody(World world, SceneElement e, ValueMap valueMap) {
float x = valueMap.getValue(e, SceneElement.VAR_X, 0f) / WORLD_SCALE;
float y = valueMap.getValue(e, SceneElement.VAR_Y, 0f) / WORLD_SCALE;
float width = valueMap.getValue(e, SceneElement.VAR_WIDTH, 1) / WORLD_SCALE;
float height = valueMap.getValue(e, SceneElement.VAR_HEIGHT, 1) / WORLD_SCALE;
// TODO what if corner is not center?
PhType phType = valueMap.getValue(e, PhysicsEf.VAR_PH_TYPE, PhType.DYNAMIC);
PhShape phShape = valueMap.getValue(e, PhysicsEf.VAR_PH_SHAPE, PhShape.RECTANGULAR);
Shape s = null;
switch (phShape) {
case CIRCULAR:
s = new CircleShape();
s.setRadius(width / 2);
break;
default:
s = new PolygonShape();
((PolygonShape) s).setAsBox(width / 2, height / 2);
}
BodyDef bd = new BodyDef();
switch (phType) {
case STATIC:
bd.type = BodyType.StaticBody;
break;
case DYNAMIC:
bd.type = BodyType.DynamicBody;
break;
}
bd.position.set(x, y);
bd.angle = valueMap.getValue(e, SceneElement.VAR_ROTATION, 0);
FixtureDef fixture = new FixtureDef();
fixture.shape = s;
fixture.density = valueMap.getValue(e, PhysicsEf.VAR_PH_DENSITY, 1f);
fixture.friction = valueMap.getValue(e, PhysicsEf.VAR_PH_FRICTION, 1f);
fixture.restitution = valueMap.getValue(e, PhysicsEf.VAR_PH_RESTITUTION, 1f);
Body body = world.createBody(bd);
body.createFixture(fixture);
body.resetMassData();
valueMap.setValue(e.getId(), VAR_PH_BODY, body);
}
/**
* @param f - fixture that is affected
* @return true if force was applied, false otherwise.
*/
private boolean ApplyToFixture(Fixture f) {
float shapeDensity = mUseDensity ? f.getDensity() : mFluidDensity;
// don't bother with buoyancy on sensors or fixtures with no density
if (f.isSensor() || (shapeDensity == 0)) {
return false;
}
Body body = f.getBody();
mAreac.set(Vector2.Zero);
mMassc.set(Vector2.Zero);
float area = 0;
// Get shape for displacement area calculations
Shape shape = f.getShape();
mSC.set(Vector2.Zero);
float sarea;
switch (shape.getType()) {
case Circle:
sarea =
B2ShapeExtensions.ComputeSubmergedArea(
(CircleShape) shape, mSurfaceNormal, mSurfaceHeight, body.getTransform(), mSC);
break;
case Chain:
sarea =
B2ShapeExtensions.ComputeSubmergedArea(
(ChainShape) shape, mSurfaceNormal, mSurfaceHeight, body.getTransform(), mSC);
break;
case Edge:
sarea =
B2ShapeExtensions.ComputeSubmergedArea(
(EdgeShape) shape, mSurfaceNormal, mSurfaceHeight, body.getTransform(), mSC);
break;
case Polygon:
sarea =
B2ShapeExtensions.ComputeSubmergedArea(
(PolygonShape) shape, mSurfaceNormal, mSurfaceHeight, body.getTransform(), mSC);
break;
default:
sarea = 0;
break;
}
area += sarea;
mAreac.x += sarea * mSC.x;
mAreac.y += sarea * mSC.y;
float mass = sarea * shapeDensity;
mMassc.x += sarea * mSC.x * shapeDensity;
mMassc.y += sarea * mSC.y * shapeDensity;
mAreac.x /= area;
mAreac.y /= area;
mMassc.x /= mass;
mMassc.y /= mass;
if (area < Float.MIN_VALUE) {
return false;
}
if (DEBUG_BUOYANCY) {
// Run debug w/HCR to see the effects of different fluid densities / linear drag
mFluidDensity = 2f;
mLinearDrag = 5;
mAngularDrag = 2;
}
// buoyancy force.
mTmp.set(mGravity).scl(-mFluidDensity * area);
body.applyForce(mTmp, mMassc, true); // multiply by -density to invert gravity
// linear drag.
mTmp.set(
body.getLinearVelocityFromWorldPoint(mAreac).sub(mFluidVelocity).mul(-mLinearDrag * area));
body.applyForce(mTmp, mAreac, true);
// angular drag.
float bodyMass = body.getMass();
if (bodyMass < 1) // prevent a huge torque from being generated...
{
bodyMass = 1;
}
float torque = -body.getInertia() / bodyMass * area * body.getAngularVelocity() * mAngularDrag;
body.applyTorque(torque, true);
return true;
}
