const double UnitSpeed = 1.0;void ThrustShip(int speed){    int NewAngle;  //used for calculating percentages    bool XNeg, YNeg;    double xdir, ydir;        XNeg = YNeg = false;    //find out what quad the angle is in    if (angle >= 90 && angle < 180)    {         XNeg = true;         NewAngle = 90 - angle;    }    else if (angle >= 180 && angle < 270)    {         XNeg = true;         YNeg = true;         NewAngle = angle - 180;    }    else if (angle >= 270 && angle < 360)    {         YNeg = true;         NewAngle = 360 - angle;    }    //calculate the precentages angle will always be in favour of the x direction.    xdir = UnitSpeed * (NewAngle / 90);    ydir = UnitSpeed * (1 - NewAngle / 90);    //check to see if we are negating    if (XNeg)         xdir = -xdir;    if (YNeg)         ydir = -ydir;    ShipPosX += xdir * speed;    ShipPosY += ydir * speed;}

quote:Original post by benishor
Richard, if I''m not wrong, your sin/cos replacement is not correct, since sin( 0 ) -> sin( 90 ) ( degrees ) does not interpolate liniary.

you tried to map the angle''s raport with respect to it''s quadran and use it as a linear interpolation time parameter, ranging from 0 to 1.

I do belive that this will transform the trygonometric circle into a 45 degrees rotated square around the origin which will result in unnatural movement

so, you''ll have to use sin() and cos(). if you want to make it faster, use lookup tables. one more hint : recalc sin and cos ONLY when angleShip is changing.

hope it helps,

benishor

---
novocaine thru yer veinz

quote:Original post by benishor
Hi Richard,

sadly, I have to say you are wrong. I took some minutes to write a small php demo of both ideas. here's the link :

http://benny.kappa.ro/sprive_movement/

p.s. even if you got the neg boolean variables wrong it still wouldn't work as intended : you're taking a value for xdir and then take the y dir value by substracting it from 1. the ship, though, will move on the distance represented by the hypotenuse. THAT distance has to be 1, not it's projection on both axis added. thus, pythagora theorem brings us to : 1 * 1 = x_dir * x_dir + y_dir * y_dir, not 1 = x_dir + y_dir.

hope it helps,

benishor


---
novocaine thru yer veinz

quote:
if (angle >= 90 && angle < 180)
{
XNeg = true;
NewAngle = 90 - angle;
}

const double DEG_TO_RAD = 0.01745; // PI / 180void ship::thrust( float speed ){   double rad_angle = angle * DEG_TO_RAD;   velx = cos(rad_angle) * speed;   vely = sin(rad_angle) * speed;   xpos += velx;   ypos += vely;}  

struct vector{   float i;   float j;};void ship::rotate( float angle, float speed ){   double rad_angle = angle * DEG_TO_RAD;   movement_vector.i = cos(rad_angle) * speed;   movement_vector.j = sin(rad_angle) * speed;}void ship::thrust(){   xpos += movement_vector.i;   ypos += movement_vector.j;}