first paragraph: converge. I know not everyone's english is that good but titles are supposed to be short and descriptive... I had to look up myself if it really was the right word tho :)
Merriam-Webster: 1 : to tend or move toward one point or one another : come together
The use is in a 3d game in set in space (free movement, negligible gravity). The code put in is to deal with collisions (between 2 objects, like ships). It's nothing too complicated.
There are 6 variables that matter here, m_fVel is the 'set' velocity (what the ship would like to be travelling at). m_fMoveVel is the 'moving' velocity, for now this changes with collisions, later on also used for if say player set to full speed, this would 'slowly' go to m_fVel. m_fAccel is how fast you can get from m_fMoveVel to m_fVel
m_Pos is the 3d position
m_Dir is the direction you want to be going in
m_Move is your current direction, should become m_Dir over time
there should also be some sort of 'm_fDir2MoveRotation' variable, i haven't gotten that far but if someone wants to put it in that would be very nice :)
problem:
the ships are shown for a frame (i can see them for a split second) then vanish (at the very least outside the camera distance which is 20,000.0f). Problem occured when i tried the improve my system, as per explained below
explanation of code:
the commented code works fine, but isn't right. What it does is make the vectors and velocity converge, but it does so in a circle where movement should be elliptical. example: if 2 ships are heading for a head-on collision, but say the left ship is a little above the right ship. They would hit, the left should would bounce left and up a bit, the right right and down a bit. But then when the left should be going a _little_ up and mostly left or right (eventually just right again no more up), it goes from left and up a bit in a perfect circle to just up to up right, to just right (just right is what you wanted, but that's not how you wanted to get there). What should have happened instead is it should have kept going a _little_ up, but less and less up, while it was going from fast left to slow left to no left-right to slow right to fast right.
Also: i'm using absolute velocity (never negative) and multiplying m_Move by -1 to make it move backwards. I'm now starting to think it would probably be easier to just make velocity positive or negative (so if from -10 to 20, just add 30) and keep m_Move always in 'forward' direction.
void CFlightShip::UpdatePos(DWORD dwTimeElapsed){
/* if(m_fMoveVel > m_fVel + 0.001f || m_fMoveVel < m_fVel - 0.001f){
if(m_fMoveVel < m_fVel){
if(m_fMoveVel < m_fVel + 0.050f)
m_fMoveVel += 0.001f * (float)dwTimeElapsed; // 1.0f / second
else
m_fMoveVel = m_fVel;
}else{
if(m_fMoveVel > m_fVel - 0.050f)
m_fMoveVel -= 0.001f * (float)dwTimeElapsed;
else
m_fMoveVel = m_fVel;
}
}*/
// New position = old position + (direction * distance moved)
m_Pos = m_Pos + m_Move * ((float)dwTimeElapsed/1000.0f * m_fMoveVel);
// m_Move = m_Move * (float)(1000-dwTimeElapsed) + m_Dir * (float)dwTimeElapsed;
// D3DXVec3Normalize(&m_Move, &m_Move);
D3DXVECTOR3 tempVec3 = m_fMoveVel * m_Move + 0.001f * (float)dwTimeElapsed * m_fAccel * m_fVel * (m_Dir-m_Move);
m_fMoveVel = sqrtf(tempVec3.x*tempVec3.x + tempVec3.y*tempVec3.y + tempVec3.z*tempVec3.z); // length of tempVec3
m_Move = tempVec3 / m_fMoveVel; // cheap normalise
}
Also useful, how i handle collisions
tempVec3 = Ship1Pos - Ship2Pos;
// fTemp = distance^2; square root is CPU buster
fTemp = tempVec3.x*tempVec3.x + tempVec3.y*tempVec3.y + tempVec3.z*tempVec3.z;
// if (distance from thispos to checkpos < radius+radius
if( fTemp < (fMaxThisRadius+fMaxCheckRadius)*(fMaxThisRadius+fMaxCheckRadius) ){
// distance between shields, always negative
//(shields are 'in' each other when ships collide... which they just did)
fTemp = sqrtf(fTemp) - (fMaxThisRadius + fMaxCheckRadius);
D3DXVec3Normalize(&tempVec3, &tempVec3);
Ship1Pos += (tempVec3 * -1 * fTemp / 2);
Ship2Pos += (tempVec3 * fTemp / 2);
m_pFlightShips.at(dwShip1)->SetPos(Ship1Pos);
m_pFlightShips.at(dwShip2)->SetPos(Ship2Pos);
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
m_pFlightShips.at(dwShip1)->SetMove(tempVec3);
m_pFlightShips.at(dwShip2)->SetMove(tempVec3 * -1.0f);
fVel = m_pFlightShips.at(dwShip2)->GetMoveVel() * 0.40f + m_pFlightShips.at(dwShip1)->GetMoveVel() * 0.40f;
m_pFlightShips.at(dwShip1)->SetMoveVel(fVel);
m_pFlightShips.at(dwShip2)->SetMoveVel(fVel);
// slows the whole thing quite a bit
if(dwShip2<dwShip1 || !bCheckAll) CollisionDetect(dwShip2, bCheckAll);
}
