//==========================================================
// Force of gravity on this entity
// Calculated by F = mass * acceleration (gravity)
// Using that information creates an always downward force
// to the Entity
//==========================================================
void Entity::gravityForce(float frameTime)
{
if (!active)
return;
force = gravity * mass;
VECTOR2 gravityV(getCenterX(), 0-getCenterY());
Graphics::Vector2Normalize(&gravityV);
gravityV *= force *frameTime;
velocity += gravityV;
}
//=============================================================================
// Force of gravity on this entity from other entity
// Adds the gravitational force to the velocity vector of this entity
// force = GRAVITY * m1 * m2 / r*r
// 2 2
// r*r = (Ax - Bx) + (Ay - By)
//=============================================================================
void Entity::gravityForce(Entity *ent, float frameTime)
{
// if either entity is not active then no gravity effect
if (!active || !ent->getActive())
return ;
rr = pow((ent->getCenterX() - getCenterX()),2) +
pow((ent->getCenterY() - getCenterY()),2);
force = gravity * ent->getMass() * mass/rr;
// --- Using vector math to create gravity vector ---
// Create vector between entities
VECTOR2 gravityV(ent->getCenterX() - getCenterX(),
ent->getCenterY() - getCenterY());
// Normalize the vector
Graphics::Vector2Normalize(&gravityV);
// Multipy by force of gravity to create gravity vector
gravityV *= force * frameTime;
// Add gravity vector to moving velocity vector to change direction
velocity += gravityV;
}
