Firing at the correct point

Blitz3D Forums/Blitz3D Programming/Firing at the correct point

JBR	(Posted 2004) [#1]

Hello, I have a craft rotating in 3d space and I want it to fire from the correct point at the correct angle. What is the best way to achieve this?

Would the following be a good (simple) way?

Have the ship and have an extra vertex where the bullet should come from. Then when the ship is rotated the extra vertex is rotated aswell.

Then I just 'read' where the extra vertex is and 'add' a bullet?

I'm also concerned about reading the vertex before the UpdateWorld command is done; should I be?

Any advice appreciated
Marg

Rook Zimbabwe

(Posted 2004) [#2]

I did something like this in my game. I have the ship fixed in the middle of the screen and I fire at the badguys passing by.

Look at the tutorials:
http://www.blitzbasic.co.nz/Community/posts.php?topic=35127
I used types to set up the bullets (Ross told me how) and to define angles and placement. I also used types to check for collision and then make the boom thig happen.

Hope that helps.

-Rook Zimbabwe

Jeppe Nielsen

(Posted 2004) [#3]

Use the Tform... commands:
use this to place your bullet five units infront of your ship:

TFormPoint 0,0,5,ship,0
PositionEntity bullet,TFormedX(),TFormedY(),TFormedZ()

And this to rotate your bullet:

TFormVector 0,0,1,ship,0
AlignToVector bullet,TFormedX(),TFormedY(),TFormedZ(),3

Now move your bullet with the MoveEntity command each frame, where speed# is the speed of the bullet:

MoveEntity bullet,0,0,speed#

jfk EO-11110

(Posted 2004) [#4]

or you could parent a pivot to the ship, and position the bullet at the pivots position and rotate it to the ships angles:

dummy=createpivot()
parententity dummy, ship
translateentity dummy,0,0,2

...

positionentity bullet, entityx(dummy,1), entityy(dummy,1), entityz(dummy,1)

rotateentity bullet, entitypitch(ship), entityyaw(ship), entityroll(ship)

and then, to move the bullet trough space, use

moveentity bullet,0,0,speed# - as in Jeppes Example