Having trouble getting world position of object - opengl

Question

I have a function called getWorldPosition that is supposed to return a vec3 representing the current position of any VisualObject (a super class I defined).
glm::vec3 VisualObject::getWorldPosition()
{
glm::mat4 totalTransformation = getParentModelMatrix() * modelMatrix;
return totalTransformation[3].xyz;
} // end getWorldPosition
I am trying to use the getWorldPosition function to calculate the distance between two objects in the world.
for (int i = enemiesOnBoard.size() - 1; i >= 0; i--){
EnemySphere* s = (EnemySphere*)enemiesOnBoard.at(i);
glm::vec3 sPosition = s->getWorldPosition();
cout << sPosition[0] << endl;
for (int j = cannonBallsOnBoard.size() - 1; j >= 0; j--){
CannonBall* cb = (CannonBall*)cannonBallsOnBoard.at(i);
glm::vec3 cbPosition = cb->getWorldPosition();
GLfloat radiiSum = s->sRadius + cb->sRadius;
GLfloat distance = calcDistance(sPosition, cbPosition);
//cout << distance << endl;
if (distance < radiiSum){
//cout << "COLLISION BABY!" << endl;
}
}
}
The problem is that every getWorldPosition is returning a vec3 with 0 for the x,y,z coordinate.
One of the spheres is defined as such,
EnemySphere* s = new EnemySphere();
enemiesOnBoard.push_back(s);
s->setShader(glutObjectShaderProgram);
s->addController(new EnemySphereController(rand() % 8 - 3.5, 1.0));
s->initialize();
addChild(s);
The relevant controller is this:
EnemySphereController::EnemySphereController(GLfloat x, GLfloat r, GLfloat t)
: Controller(), startX(x), rate(r), translation(t)
{ }
void EnemySphereController::update(float elapsedTimeSec){
if (translation < 3.9f){
translation += elapsedTimeSec * rate;
}
else {
target->getParent()->removeChild(target->getObjectSerialNumber());
}
glm::mat4 t4;
t4 = glm::translate(glm::mat4(1.0f), glm::vec3(startX, -2.50f, translation)); //add 0.5 because the sphere is calculated from the center
target->fixedTransformation = t4;
}
I know this is a complicated problem, but do you guys have any ideas on where I can start?

Answer 1

As I know, the world position resides in glm::vec3(mat[3], mat[7], mat[11]), so you should change your function to:
glm::vec3 VisualObject::getWorldPosition()
{
glm::mat4 totalTransformation = getParentModelMatrix() * modelMatrix;
return glm::vec3(totalTransformation[3], totalTransformation[7], totalTransformation[11]);
} // end getWorldPosition
The part which you were using as translation is used for projection.