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From: Lewis_Evans@Playstation.sony.com
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: vectored bullets code sample
Date: 7 Jan 1998 17:17:28 -0000
Organization: Sony Computer Entertainment Europe - 119.SS5
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From: Lewis_Evans@Playstation.sony.com
To: news@playstation.co.uk

I cannot say much about the sample code given, because I can't see what
AdvanceModel does.

The one oddity is:

     // here: position of car is assigned to <rotation vector?????> of
bullet?
     // surely should assign to position of bullet?
        theBullet->rotation.vx = theCar.gsObjectCoord.coord.t[0];
        theBullet->rotation.vy = theCar.gsObjectCoord.coord.t[1];
        theBullet->rotation.vz = theCar.gsObjectCoord.coord.t[2];

     // here: rotation vector of bullet is assigned to position of
bullet?????
        theBullet->gsObjectCoord.coord.t[0] = theBullet->rotation.vx;
        theBullet->gsObjectCoord.coord.t[1] = theBullet->rotation.vy;
        theBullet->gsObjectCoord.coord.t[2] = theBullet->rotation.vz;

     What really needs to happen is:
     when you create a bullet, set its position to the centre / front edge
of the car.
     Then you want the velocity of the bullet to point in the direction
that the car faces in.
     This vector is directly obtainable from the car matrix
(COORD2.coord.m);
     the way it faces is the car matrix z axis, eg use

     worldVelocityVector.vx = car.coord.m[0][2];
     worldVelocityVector.vy = car.coord.m[1][2];
     worldVelocityVector.vz = car.coord.m[2][2];

     [Note: should scale for absolute bullet speed, ie each element *=
bulletSpeed, then /= ONE].

     [The above works because a rotation matrix is really just an
expression of three axes:
     the car x, y and z axes, each expressed in world terms].

     now the worldVelocityVector points in the direction the car faces.
Each frame, update the bullet's
     position by the velocity, and there it is.

     See the SCEE demos flying and dungeon for more examples of ships
shooting bullets
     in the direction they are facing.


          Lewis






To:       Lewis Evans
cc:
From:     news @ playstation.co.uk
Subject:  vectored bullets code sample:scee.yaroze.programming.3d_graphics




From: "Linda J. Hodge" <hodgke@earthlink.net>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: vectored bullets code sample
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
hello,Im trying to make a bullet fly from the center of the Car in the
current vector of the car and proceed,like the missiles in twisted
metal.I have some code but it doesnt seem to work.All it displays is the
bullet tmd around the car and wherever the car moves the bullet rotates
around the car.
code Sample:
void Shoot(PlayerStructType2 *theBullet,
                 unsigned long *lModelAddress)
         {
         DrawPlayer(theBullet,&othWorld[currentBuffer]);
         lModelAddress++;
         GsMapModelingData((unsigned long *)lModelAddress);
         GsInitCoordinate2(WORLD, &theBullet->gsObjectCoord);
         lModelAddress++;  lModelAddress++;
        GsLinkObject4((unsigned
long*)lModelAddress,&theBullet->gsObjectHandler,0);
        theBullet->gsObjectHandler.coord2 = &theBullet->gsObjectCoord;
        theBullet->rotation.vx = theCar.gsObjectCoord.coord.t[0];
        theBullet->rotation.vy = theCar.gsObjectCoord.coord.t[1];
        theBullet->rotation.vz = theCar.gsObjectCoord.coord.t[2];
        theBullet->gsObjectCoord.coord.t[0] = theBullet->rotation.vx;
        theBullet->gsObjectCoord.coord.t[1] = theBullet->rotation.vy;
        theBullet->gsObjectCoord.coord.t[2] = theBullet->rotation.vz;
AdvanceModel(&theBullet->gsObjectCoord,&theBullet->rotation,&theBullet->spe
ed,256);
        theBullet->gsObjectCoord.flg = 0;
}
I call this function when the pad is pressed.
-Austin