physics.cpp

#include "physics.h"
 
 
physics::physics() 
{
    m_gravity = XMVectorSet(0.0f, -9.81f, 0.0f, 0.0f); // initialize the gravity vector
}
 
physics::physics(const physics& other)
{
    m_gravity = other.m_gravity; // Copy the gravity value
}
 
physics::~physics()
{
}
 
// Get the gravity value
XMVECTOR physics::GetGravity() const
{
    return m_gravity;
}
 
// Define the gravity value
void physics::SetGravity(XMVECTOR gravity)
{
    m_gravity = gravity;
}
 
// Apply gravity to an object
void physics::ApplyGravity(object* object, float dragValue)
{
    if (this == nullptr || object == nullptr) // Verify if 'this' and 'object' are not null
    {
        return;
    }
 
    if (!object->IsGrounded()) // Verify if the object is grounded
    {
        // Calculate the acceleration caused by gravity
        XMVECTOR gravityAcceleration = m_gravity / object->GetMass();
 
        // Add the gravity acceleration to the object's current acceleration
        object->SetAcceleration(object->GetAcceleration() + gravityAcceleration);
 
        // Calculate the acceleration caused by drag
        XMVECTOR dragAcceleration = -object->GetVelocity() * dragValue / object->GetMass();
 
        // Add the drag acceleration to the object's current acceleration
        object->SetAcceleration(object->GetAcceleration() + dragAcceleration);
 
        // Get the object velocity
        XMVECTOR velocity = object->GetVelocity();
 
        // Update the velocity with the object's acceleration
        velocity += object->GetAcceleration();
 
        // Set the new velocity
        object->SetVelocity(velocity);
    }
}
 
void physics::AddForce(object* object, XMVECTOR force)
{
    if (object == nullptr) // Verify if the object is not null
    {
        return;
    }
 
    // Get the mass of the object
    float mass = object->GetMass();
 
    // Calculate the acceleration caused by the force
    XMVECTOR acceleration = force / mass;
 
    // Add the acceleration to the object's current acceleration
    object->SetAcceleration(object->GetAcceleration() + acceleration);
}
 
bool physics::IsColliding(object* object1, object* object2)
{
    ObjectType type1 = object1->GetType();
    ObjectType type2 = object2->GetType();
 
    if (type1 == ObjectType::Unknown || type2 == ObjectType::Unknown)
    {
        return false;
    }
 
    if (type1 == ObjectType::Sphere && type2 == ObjectType::Sphere)
    {
        return SpheresOverlap(object1, object2);
    }
    if ((type1 == ObjectType::Cube && type2 == ObjectType::Sphere) ||
        (type1 == ObjectType::Sphere && type2 == ObjectType::Cube))
    {
        if (type1 == ObjectType::Cube)
        {
            return SphereCubeOverlap(object1, object2);
        }
        else if (type1 == ObjectType::Sphere)
        {
            return SphereCubeOverlap(object2, object1);
        }
    }
    else
    {
        return CubesOverlap(object1, object2);
    }
 
    return false;
}
 
 
// AABB method for collision detection //
 
bool physics::CubesOverlap(object* cube1, object* cube2)
{
    XMVECTOR position1 = cube1->GetPosition();
    XMVECTOR position2 = cube2->GetPosition();
 
    XMVECTOR scale1 = cube1->GetScale();
    XMVECTOR scale2 = cube2->GetScale();
 
    XMVECTOR min1 = position1 - scale1;
    XMVECTOR max1 = position1 + scale1;
    XMVECTOR min2 = position2 - scale2;
    XMVECTOR max2 = position2 + scale2;
 
    return (min1.m128_f32[0] <= max2.m128_f32[0] && max1.m128_f32[0] >= min2.m128_f32[0] &&
        min1.m128_f32[1] <= max2.m128_f32[1] && max1.m128_f32[1] >= min2.m128_f32[1] &&
        min1.m128_f32[2] <= max2.m128_f32[2] && max1.m128_f32[2] >= min2.m128_f32[2]);
}
 
bool physics::SpheresOverlap(object* sphere1, object* sphere2)
{
    XMVECTOR position1 = sphere1->GetPosition();
    XMVECTOR position2 = sphere2->GetPosition();
 
    XMVECTOR scale1 = sphere1->GetScale() / 2;
    XMVECTOR scale2 = sphere2->GetScale() / 2;
 
    float distance = sqrt(
        (position1.m128_f32[0] - position2.m128_f32[0]) * (position1.m128_f32[0] - position2.m128_f32[0]) +
        (position1.m128_f32[1] - position2.m128_f32[1]) * (position1.m128_f32[1] - position2.m128_f32[1]) +
        (position1.m128_f32[2] - position2.m128_f32[2]) * (position1.m128_f32[2] - position2.m128_f32[2])
    );
 
    float radius1 = XMVectorGetX(XMVector3Length(scale1));
    float radius2 = XMVectorGetX(XMVector3Length(scale2));
 
    return distance < radius1 + radius2;
}
 
bool physics::SphereCubeOverlap(object* cube, object* sphere)
{
    XMVECTOR position1 = cube->GetPosition();
    XMVECTOR position2 = sphere->GetPosition();
 
    XMVECTOR scale1 = cube->GetScale();
    XMVECTOR scale2 = XMVectorScale(sphere->GetScale(), 0.5f);
 
    XMVECTOR min1 = position1 - scale1;
    XMVECTOR max1 = position1 + scale1;
 
    // Get box closest point to sphere center by clamping
    float x = max(min1.m128_f32[0], min(position2.m128_f32[0], max1.m128_f32[0]));
    float y = max(min1.m128_f32[1], min(position2.m128_f32[1], max1.m128_f32[1]));
    float z = max(min1.m128_f32[2], min(position2.m128_f32[2], max1.m128_f32[2]));
 
    // This is the same as SpheresOverlap
    float distance = sqrt(
        (x - position2.m128_f32[0]) * (x - position2.m128_f32[0]) +
        (y - position2.m128_f32[1]) * (y - position2.m128_f32[1]) +
        (z - position2.m128_f32[2]) * (z - position2.m128_f32[2])
    );
 
    float radius = XMVectorGetX(XMVector3Length(scale2));
 
    return distance < radius;
}