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# Integration of AI into objects... Also, will this method work?

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Hello all! I'm new to the world of AI and have a question regarding my current game. I'm making a simple Space Invaders clone, and am wondering how AI is implemented. I don't know if you embed the AI directly in the objects member functions, or what! However, if you do, then I've written the following pseudo-code to do the enemy ships firing. Is this a good approach for simple AI, or am I way off base?

enum ENEMY_DIRECTION
{
IMMOBILE=0, TOWARDS=1, STOPPED=2
};

//*********************************************************************
// bool CShip::CheckAttack(const CShip& enemy)
// This function determines if a craft should fire at the enemy craft
// For calculations, it assumes NO acceleration.. All instantaneous
// craft velocities are == to the max velocity or the ship is at rest
// RETURN VALUES: true means attack should be performed
//                false means attack should not be performed
// NOTE: THIS DOES NOT YET TAKE INTO ACCOUNT THE ACTIVE WEAPON!  IF
//*********************************************************************
bool CShip::CheckAttack(const CShip& enemy)
{
/*
CShip(THIS_SHIP)
|   | \
|  \ z
|      |       |-----      x     CShip(enemy)
*/
float enemyX = enemy.getX();
float enemyY = enemy.getY();

float x = enemyX - m_position.x;
float y = enemyY - m_position.y;

//float xsquared = x*x;

//float ysquared = y*y;

//float zsquared = (xsquared + ysquared);

ENEMY_DIRECTION enemyDir = AWAY;

//* Find out how far away the enemy craft is, then determine

//* if it is coming towards me, away from me, or sitting still

float enemySpeed = enemy.getSpeed();

if(enemySpeed != 0 && m_position.x > enemyX)
if(x > 0)
enemyDir = TOWARDS;

if(enemySpeed != 0 && m_position.x < enemyX)
if(x < 0)
enemyDir = TOWARDS;

if(enemySpeed == 0)
enemyDir = STOPPED;

if(enemyDir == STOPPED)
{
if(enemyX == m_position.x)
return true;  //* Sitting duck

else
return false; //* Lame craft is hiding in corner

}

float timeUntilBulletHits = y / getActiveWeaponMuzzleVelocity();
float timeUntilEnemyBelow = x / enemySpeed;

// If bullet can hit ground in less time than it would take for the enemy

// to travel directly below, I can possibly score a hit

// If bullet time is greater than travel time, the ship could go right past

// way before my bullet would be able to hit it.

if(timeUntilBulletHits >= timeUntilEnemyBelow*0.95f &&
timeUntilBulletHits <= timeUntilEnemyBelow)
{
if(TOWARDS_ME)
{ //* present course will bring enemy within fire-range

return true;
}
}

return false;
}

[edited by - camcbri on May 31, 2002 3:53:04 PM] [edited by - camcbri on May 31, 2002 3:56:53 PM]

wrong forum

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as far as i can tell, the original space invaders just had them fire randomly, and more so at higher levels (with an occasional bomb or homing bomb).
or am i thinking of a different game?

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well.. i hope to make the enemies a little more accurate than the original if they really did just fire randomly!

basically, what i''m doing is determining if the player is heading toward the enemy, away from, or sitting still.

if he''s sitting still and under the enemy, i return true but if he''s still and not under me, I return false.

then, i figure out how long it would take for the bullet to get to the player if he were moving toward the enemy. If he can beat the bullet by a long ways and pass under me, I don''t want to fire. SO, I return true if the player ship is within 95% and 100% of the distance that he could traverse before getting directly under the current enemy ship position..

it''s all boils down to velocity = distance / time, but I wanted to ask if there are any shortcuts, or if I shouldn''t put this into the CShip class at all, but in some AI library? I remember very little from my physics classes so velocity was the first thing I thought of!

I thought that this would work for a demo mode too... If both the player ship and the enemy ships are derived from CShip, then the computer could play both sides! Now I just have to teach it how to evade...

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