void TranslateToObjectSpace(PhysicsObject po)
{
// handy function to move into object space given a PhysicsObject
gl.Translatef(po.Location.X, po.Location.Y, po.Location.Z);
}
void ProcessShip(float elapsedTime, float sceneDepth)
{
myShip.Velocity = GetShipVelocityVector();
// this makes the ship rotate slowly if the user turns it.
// the ship can do a max turn of 360 degrees in 1 second, so enforce that
float angle = ZRotationFromVector(myShip.Velocity);
float maxRotateAllowed = 360f * elapsedTime;
float delta = angle - myShipRotation;
if (Math.Abs(delta) > maxRotateAllowed)
{
if ((delta > 0 && delta < 180) || delta < -180)
myShipRotation += maxRotateAllowed;
else
myShipRotation -= maxRotateAllowed;
}
else
{
myShipRotation = angle;
}
if (myShipRotation < 0)
myShipRotation += 360;
else if (myShipRotation > 360)
myShipRotation -= 360;
// move the ship
myShip = ApplyPhysics(myShip, Vector4f.Zero, elapsedTime, true);
gl.PushMatrix();
myShip.Location.Z = sceneDepth;
TranslateToObjectSpace(myShip);
if (!float.IsNaN(myShipRotation))
gl.Rotatef(myShipRotation, 0, 0, 1);
// draw the ship
myShipTexture.DrawCenteredSprite();
gl.PopMatrix();
}
// create a bullet flying at the given angle
// the starting point is the ship
PhysicsObject CreateBullet(float angle)
{
PhysicsObject bullet = new PhysicsObject();
bullet.Location = myShip.Location;
bullet.Velocity.X = (float)Math.Cos(angle / 180 * Math.PI);
bullet.Velocity.Y = (float)Math.Sin(angle / 180 * Math.PI);
bullet.Velocity = bullet.Velocity.Normalize().Scale(500);
return bullet;
}
bool IsInBounds(PhysicsObject po)
{
// return whether the object is in screen bounds or not
return po.Location.X < myWidth / 2 && po.Location.X > -myWidth / 2 && po.Location.Y < myHeight / 2 && po.Location.Y > -myHeight / 2;
}
PhysicsObject ApplyPhysics(PhysicsObject po, Vector4f acceleration, float elapsedTime, bool rollOver)
{
// update the position and velocity of the object
po.Location += po.Velocity.Scale(elapsedTime);
po.Velocity += acceleration.Scale(elapsedTime);
if (rollOver)
{
// roll it over the edge of the screen if necessary
Rollover(ref po.Location.X, myWidth);
Rollover(ref po.Location.Y, myHeight);
}
return po;
}
