// This function handles the collision between the ray and the ground
// Information about the interaction is passed in colEntry
void World::ground_collide_handler(const CollisionEntry& colEntry)
{
// Set the ball to the appropriate Z value for it to be exactly on the ground
NodePath renderNp = m_windowFrameworkPtr->get_render();
float newZ = colEntry.get_surface_point(renderNp).get_z();
m_ballRootNp.set_z(newZ + 0.4);
// Find the acceleration direction. First the surface normal is crossed with
// the up vector to get a vector perpendicular to the slope
LVector3f norm = colEntry.get_surface_normal(renderNp);
LVector3f accelSide = norm.cross(UP);
// Then that vector is crossed with the surface normal to get a vector that
// points down the slope. By getting the acceleration in 3D like this rather
// than in 2D, we reduce the amount of error per-frame, reducing jitter
m_accelV = norm.cross(accelSide);
}
// This function handles the collision between the ball and a wall
void World::wall_collide_handler(const CollisionEntry& colEntry)
{
// First we calculate some numbers we need to do a reflection
NodePath renderNp = m_windowFrameworkPtr->get_render();
// The normal of the wall
LVector3f norm = colEntry.get_surface_normal(renderNp) * -1;
// The current speed
float curSpeed = m_ballV.length();
// The direction of travel
LVector3f inVec = m_ballV / curSpeed;
// Angle of incidence
float velAngle = norm.dot(inVec);
LPoint3f hitDir = colEntry.get_surface_point(renderNp) - m_ballRootNp.get_pos();
hitDir.normalize();
// The angle between the ball and the normal
float hitAngle = norm.dot(hitDir);
// Ignore the collision if the ball is either moving away from the wall
// already (so that we don't accidentally send it back into the wall)
// and ignore it if the collision isn't dead-on (to avoid getting caught on
// corners)
if(velAngle > 0 && hitAngle > .995)
{
// Standard reflection equation
LVector3f reflectVec = (norm * norm.dot(inVec * -1) * 2) + inVec;
// This makes the velocity half of what it was if the hit was dead-on
// and nearly exactly what it was if this is a glancing blow
m_ballV = reflectVec * (curSpeed * (((1-velAngle)*.5)+.5));
// Since we have a collision, the ball is already a little bit buried in
// the wall. This calculates a vector needed to move it so that it is
// exactly touching the wall
LPoint3f disp = (colEntry.get_surface_point(renderNp) -
colEntry.get_interior_point(renderNp));
LPoint3f newPos = m_ballRootNp.get_pos() + disp;
m_ballRootNp.set_pos(newPos);
}
}
