Parenting lights

Hello:
I was trying to parent a SIO2lamp with a SIO2object.
I can parent two objects with
_SIO2object2->_SIO2transform->_SIO2parent = _SIO2object->_SIO2transform;
and it works grate.
But if I try to parent a light with
_SIO2lamp->_SIO2transform->_SIO2parent = _SIO2object->_SIO2transform;
it doesn't work.
I tried to create an auxiliar child object and, in every frame, give the position of the object to a light, but it doesn't work because the location of the child objet doesn't change although the parent was moving.
Can anyone help me, please?
Thank you!

Because of OpenGL the lamps have to be rendered this way:

Code:


      memcpy( &l[ 0 ], _SIO2lamp->_SIO2transform->loc, 12 );
      l[ 3 ] = 1.0f;
      
      glLightfv( _SIO2lamp->index, GL_POSITION, &l[ 0 ] );


If you want to parent it to an object, you'll have to do the calculation manually...

Thank you.
I will try to set the position manualy.
But, also, I need to know how to get the global position of a child object (for non related light issues).
I am checking in tutorial 14 as explains this topic
https://sio2interactive.forumotion.net/sio2-engine-f3/child-object-unchanged-trans-t626.htm
but, like my companions, I didn't found a solution. When asking the location property, it always returns the same value although the parent is moving (rotating, in fact, like an earth-moon system).
Thank you so much.

Location always need to be in world space, the parent child relationship of the matrix have to be relative to the parent.

Thanks for your replies.
I wrote two functions that allow me to see the global location of a child object.
I hope this will be useful for someone.

Code:


void multMatrix(SIO2transform* pDest, SIO2transform* pOrig2, SIO2transform* pOrig1)
{   
   pDest->mat[0] = pOrig1->mat[0] * pOrig2->mat[0] + pOrig1->mat[4] * pOrig2->mat[1] + pOrig1->mat[8] * pOrig2->mat[2] + pOrig1->mat[12] * pOrig2->mat[3];
   pDest->mat[1] = pOrig1->mat[1] * pOrig2->mat[0] + pOrig1->mat[5] * pOrig2->mat[1] + pOrig1->mat[9] * pOrig2->mat[2] + pOrig1->mat[13] * pOrig2->mat[3];
   pDest->mat[2] = pOrig1->mat[2] * pOrig2->mat[0] + pOrig1->mat[6] * pOrig2->mat[1] + pOrig1->mat[10] * pOrig2->mat[2] + pOrig1->mat[14] * pOrig2->mat[3];
   pDest->mat[3] = pOrig1->mat[3] * pOrig2->mat[0] + pOrig1->mat[7] * pOrig2->mat[1] + pOrig1->mat[11] * pOrig2->mat[2] + pOrig1->mat[15] * pOrig2->mat[3];
   
   pDest->mat[4] = pOrig1->mat[0] * pOrig2->mat[4] + pOrig1->mat[4] * pOrig2->mat[5] + pOrig1->mat[8] * pOrig2->mat[6] + pOrig1->mat[12] * pOrig2->mat[7];
   pDest->mat[5] = pOrig1->mat[1] * pOrig2->mat[4] + pOrig1->mat[5] * pOrig2->mat[5] + pOrig1->mat[9] * pOrig2->mat[6] + pOrig1->mat[13] * pOrig2->mat[7];
   pDest->mat[6] = pOrig1->mat[2] * pOrig2->mat[4] + pOrig1->mat[6] * pOrig2->mat[5] + pOrig1->mat[10] * pOrig2->mat[6] + pOrig1->mat[14] * pOrig2->mat[7];
   pDest->mat[7] = pOrig1->mat[3] * pOrig2->mat[4] + pOrig1->mat[7] * pOrig2->mat[5] + pOrig1->mat[11] * pOrig2->mat[6] + pOrig1->mat[15] * pOrig2->mat[7];
   
   pDest->mat[8] = pOrig1->mat[0] * pOrig2->mat[8] + pOrig1->mat[4] * pOrig2->mat[9] + pOrig1->mat[8] * pOrig2->mat[10] + pOrig1->mat[12] * pOrig2->mat[11];
   pDest->mat[9] = pOrig1->mat[1] * pOrig2->mat[8] + pOrig1->mat[5] * pOrig2->mat[9] + pOrig1->mat[9] * pOrig2->mat[10] + pOrig1->mat[13] * pOrig2->mat[11];
   pDest->mat[10] = pOrig1->mat[2] * pOrig2->mat[8] + pOrig1->mat[6] * pOrig2->mat[9] + pOrig1->mat[10] * pOrig2->mat[10] + pOrig1->mat[14] * pOrig2->mat[11];
   pDest->mat[11] = pOrig1->mat[3] * pOrig2->mat[8] + pOrig1->mat[7] * pOrig2->mat[9] + pOrig1->mat[11] * pOrig2->mat[10] + pOrig1->mat[15] * pOrig2->mat[11];
   
   pDest->mat[12] = pOrig1->mat[0] * pOrig2->mat[12] + pOrig1->mat[4] * pOrig2->mat[13] + pOrig1->mat[8] * pOrig2->mat[14] + pOrig1->mat[12] * pOrig2->mat[15];
   pDest->mat[13] = pOrig1->mat[1] * pOrig2->mat[12] + pOrig1->mat[5] * pOrig2->mat[13] + pOrig1->mat[9] * pOrig2->mat[14] + pOrig1->mat[13] * pOrig2->mat[15];
   pDest->mat[14] = pOrig1->mat[2] * pOrig2->mat[12] + pOrig1->mat[6] * pOrig2->mat[13] + pOrig1->mat[10] * pOrig2->mat[14] + pOrig1->mat[14] * pOrig2->mat[15];
   pDest->mat[15] = pOrig1->mat[3] * pOrig2->mat[12] + pOrig1->mat[7] * pOrig2->mat[13] + pOrig1->mat[11] * pOrig2->mat[14] + pOrig1->mat[15] * pOrig2->mat[15];
}

void applyParentTransform( SIO2transform* pDest, SIO2transform* pOrig, SIO2transform* pParent)
{         
   SIO2transform* PosP = sio2TransformInit();
   PosP->mat[0] = 1; PosP->mat[1] = 0; PosP->mat[2] = 0; PosP->mat[3] = pParent->loc->x;
   PosP->mat[4] = 0; PosP->mat[5] = 1; PosP->mat[6] = 0; PosP->mat[7] = pParent->loc->y;
   PosP->mat[8] = 0; PosP->mat[9] = 0; PosP->mat[10] = 1; PosP->mat[11] = pParent->loc->z;
   PosP->mat[12] = 0;   PosP->mat[13] = 0;   PosP->mat[14] = 0;   PosP->mat[15] = 1;
   
   SIO2transform* Rot1 = sio2TransformInit();
   float cos_v = cosf( pParent->rot->x * SIO2_DEG_TO_RAD );
   float sin_v = sinf( pParent->rot->x * SIO2_DEG_TO_RAD );
   Rot1->mat[0] = 1;   Rot1->mat[1] = 0; Rot1->mat[2] = 0; Rot1->mat[3] = 0;
   Rot1->mat[4] = 0; Rot1->mat[5] = cos_v; Rot1->mat[6] = -sin_v; Rot1->mat[7] = 0;
   Rot1->mat[8] = 0; Rot1->mat[9] = sin_v; Rot1->mat[10] = cos_v; Rot1->mat[11] = 0;
   Rot1->mat[12] = 0;   Rot1->mat[13] = 0;   Rot1->mat[14] = 0;   Rot1->mat[15] = 1;
   
   SIO2transform* Rot2 = sio2TransformInit();
   cos_v = cosf( pParent->rot->y * SIO2_DEG_TO_RAD );
   sin_v = sinf( pParent->rot->y * SIO2_DEG_TO_RAD );
   Rot2->mat[0] = cos_v; Rot2->mat[1] = 0; Rot2->mat[2] = sin_v; Rot2->mat[3] = 0;
   Rot2->mat[4] = 0; Rot2->mat[5] = 1; Rot2->mat[6] = 0; Rot2->mat[7] = 0;
   Rot2->mat[8] = -sin_v; Rot2->mat[9] = 0; Rot2->mat[10] = cos_v; Rot2->mat[11] = 0;
   float aux = Rot2->mat[8];
   Rot2->mat[12] = 0;   Rot2->mat[13] = 0;   Rot2->mat[14] = 0;   Rot2->mat[15] = 1;
   
   SIO2transform* Rot3 = sio2TransformInit();
   cos_v = cosf( pParent->rot->z * SIO2_DEG_TO_RAD );
   sin_v = sinf( pParent->rot->z * SIO2_DEG_TO_RAD );
   Rot3->mat[0] = cos_v; Rot3->mat[1] = -sin_v; Rot3->mat[2] = 0; Rot3->mat[3] = 0;
   Rot3->mat[4] = sin_v; Rot3->mat[5] = cos_v; Rot3->mat[6] = 0; Rot3->mat[7] = 0;
   Rot3->mat[8] = 0; Rot3->mat[9] = 0; Rot3->mat[10] = 1; Rot3->mat[11] = 0;
   Rot3->mat[12] = 0;   Rot3->mat[13] = 0;   Rot3->mat[14] = 0;   Rot3->mat[15] = 1;

   
   SIO2transform* pAux0 = sio2TransformInit();
   SIO2transform* pAux1 = sio2TransformInit();
   SIO2transform* pAux2 = sio2TransformInit();
   multMatrix(pAux0, PosP, Rot1);
   multMatrix(pAux1, pAux0, Rot2);
   multMatrix(pAux2, pAux1, Rot3);
      
   float fX = pAux2->mat[0]*pOrig->loc->x + pAux2->mat[1]*pOrig->loc->y + pAux2->mat[2]*pOrig->loc->z;
   float fY = pAux2->mat[4]*pOrig->loc->x + pAux2->mat[5]*pOrig->loc->y + pAux2->mat[6]*pOrig->loc->z;
   float fZ = pAux2->mat[8]*pOrig->loc->x + pAux2->mat[9]*pOrig->loc->y + pAux2->mat[10]*pOrig->loc->z;
       
   pDest->loc->x = fX;
   pDest->loc->y = fY;
   pDest->loc->z = fZ;
      
   sio2TransformFree(Rot1);
   sio2TransformFree(Rot2);
   sio2TransformFree(Rot3);
   sio2TransformFree(pAux0);
   sio2TransformFree(pAux1);
   sio2TransformFree(pAux2);
}


The first one, multMatrix write in the matrix of pDest the result of pOrig2*pOrig1.
The second one is to give to a pDest transform the result of aply the transform of pParent to pOrig.
Using applyParentTransform I can see in the pDest transform, the global position of pOrig.

But I still have a problem.
In my game, I'm using rigid bodies (_SIO2object->_SIO2objectphysic->_btRigidBody). And I'm moving it by applying torques to it.
The problem to apply torques is that the rotation in SIO2transform->rot is going crazy (for example, aplying an x,0,0 torque, the rotation changes also in y axis) and I can't apply my functions correctly.
Has anyone know how to convert the torque rotation to a standard rotation (or extract the actual standard rotation from the object)?
Thanks so much!